diff --git a/app/src/main/java/net/micode/notes/data/Contact.java b/app/src/main/java/net/micode/notes/data/Contact.java
index 35ed74d..d97ac5d 100644
--- a/app/src/main/java/net/micode/notes/data/Contact.java
+++ b/app/src/main/java/net/micode/notes/data/Contact.java
@@ -1,78 +1,73 @@
-/*//如果查询结果不为空且有数据
- * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)//如果查询结果不为空且有数据
- *如果查询结果不为空且有数据//如果查询结果不为空且有数据
- * Licensed under the Apache License, Version 2.0 (the "License");//如果查询结果不为空且有数据
- * you may not use this file except in compliance with the License.//如果查询结果不为空且有数据
- * You may obtain a copy of the License at//如果查询结果不为空且有数据//如果查询结果不为空且有数据
+/*
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
  *
- *        http://www.apache.org/licenses/LICENSE-2.0//如果查询结果不为空且有数据
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
- * Unless required by applicable law or agreed to in writing, software//如果查询结果不为空且有数据
- * distributed under the License is distributed on an "AS IS" BASIS,//如果查询结果不为空且有数据
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.//如果查询结果不为空且有数据
- * See the License for the specific language governing permissions and//如果查询结果不为空且有数据
- * limitations under the License.//如果查询结果不为空且有数据
- */// //如果查询结果不为空且有数据
-// 如果查询结果不为空且有数据
-package net.micode.notes.data; // 定义包名
-//如果查询结果不为空且有数据
-import android.content.Context; // 导入Context类
-import android.database.Cursor; // 导入Cursor类
-import android.provider.ContactsContract.CommonDataKinds.Phone; // 导入Phone类
-import android.provider.ContactsContract.Data; // 导入Data类
-import android.telephony.PhoneNumberUtils; // 导入PhoneNumberUtils类
-import android.util.Log; // 导入Log类
-// 如果查询结果不为空且有数据
-import java.util.HashMap; // 导入HashMap类
-// 如果查询结果不为空且有数据
-public class Contact {//如果查询结果不为空且有数据
-    private static HashMap<String, String> sContactCache; // 定义一个静态HashMap用于缓存联系人信息
-    private static final String TAG = "Contact"; // 定义日志标签// 如果查询结果不为空且有数据
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.micode.notes.data;
+
+import android.content.Context;
+import android.database.Cursor;
+import android.provider.ContactsContract.CommonDataKinds.Phone;
+import android.provider.ContactsContract.Data;
+import android.telephony.PhoneNumberUtils;
+import android.util.Log;
+
+import java.util.HashMap;
+
+public class Contact {
+    private static HashMap<String, String> sContactCache;
+    private static final String TAG = "Contact";
+
+    private static final String CALLER_ID_SELECTION = "PHONE_NUMBERS_EQUAL(" + Phone.NUMBER
+    + ",?) AND " + Data.MIMETYPE + "='" + Phone.CONTENT_ITEM_TYPE + "'"
+    + " AND " + Data.RAW_CONTACT_ID + " IN "
+            + "(SELECT raw_contact_id "
+            + " FROM phone_lookup"
+            + " WHERE min_match = '+')";
+
+    public static String getContact(Context context, String phoneNumber) {
+        if(sContactCache == null) {
+            sContactCache = new HashMap<String, String>();
+        }
+
+        if(sContactCache.containsKey(phoneNumber)) {
+            return sContactCache.get(phoneNumber);
+        }
+
+        String selection = CALLER_ID_SELECTION.replace("+",
+                PhoneNumberUtils.toCallerIDMinMatch(phoneNumber));
+        Cursor cursor = context.getContentResolver().query(
+                Data.CONTENT_URI,
+                new String [] { Phone.DISPLAY_NAME },
+                selection,
+                new String[] { phoneNumber },
+                null);
 
-    // 定义查询条件字符串，用于匹配电话号码// 如果查询结果不为空且有数据
-    private static final String CALLER_ID_SELECTION = "PHONE_NUMBERS_EQUAL(" + Phone.NUMBER// 如果查询结果不为空且有数据
-            + ",?) AND " + Data.MIMETYPE + "='" + Phone.CONTENT_ITEM_TYPE + "'"// 如果查询结果不为空且有数据
-            + " AND " + Data.RAW_CONTACT_ID + " IN "// 如果查询结果不为空且有数据
-            + "(SELECT raw_contact_id "// 如果查询结果不为空且有数据
-            + " FROM phone_lookup"// 如果查询结果不为空且有数据
-            + " WHERE min_match = '+')";// 如果查询结果不为空且有数据
-    //如果查询结果不为空且有数据
-    // 获取联系人信息的方法// 如果查询结果不为空且有数据
-    public static String getContact(Context context, String phoneNumber) {// 如果查询结果不为空且有数据
-        if(sContactCache == null) { // 如果缓存为空，则初始化
-            sContactCache = new HashMap<String, String>();// 如果查询结果不为空且有数据
-        }// 如果查询结果不为空且有数据
-// 如果查询结果不为空且有数据
-        if(sContactCache.containsKey(phoneNumber)) { // 如果缓存中已存在该电话号码，直接返回缓存的联系人姓名
-            return sContactCache.get(phoneNumber);// 如果查询结果不为空且有数据
-        }// 如果查询结果不为空且有数据
-// 如果查询结果不为空且有数据
-        // 替换查询条// 如果查询结果不为空且有数据件中的占位符
-        String selection = CALLER_ID_SELECTION.replace("+",// 如果查询结果不为空且有数据
-                PhoneNumberUtils.toCallerIDMinMatch(phoneNumber));// 如果查询结果不为空且有数据
-        // 查询联系人信息
-        Cursor cursor = context.getContentResolver().query(// 如果查询结果不为空且有数据
-                Data.CONTENT_URI,// 如果查询结果不为空且有数据
-                new String [] { Phone.DISPLAY_NAME },// 如果查询结果不为空且有数据
-                selection,// 如果查询结果不为空且有数据
-                new String[] { phoneNumber },// 如果查询结果不为空且有数据
-                null);// 如果查询结果不为空且有数据
-//如果查询结果不为空且有数据
-        if (cursor != null && cursor.moveToFirst()) { // 如果查询结果不为空且有数据
-            try {//如果查询结果不为空且有数据
-                String name = cursor.getString(0); // 获取联系人姓名
-                sContactCache.put(phoneNumber, name); // 将联系人信息缓存
-                return name; // 返回联系人姓名
-            } catch (IndexOutOfBoundsException e) { // 捕获异常
-                Log.e(TAG, " Cursor get string error " + e.toString()); // 打印错误日志
-                return null; // 返回空
-            } finally {// 返回空
-                cursor.close(); // 关闭游标
-            }// 返回空
-        } else {// 返回空
-            Log.d(TAG, "No contact matched with number:" + phoneNumber); // 打印未匹配到联系人日志
-            return null; // 返回空
-        }// 返回空
-    }// 返回空
-}// 返回空
-//如果查询结果不为空且有数据
\ No newline at end of file
+        if (cursor != null && cursor.moveToFirst()) {
+            try {
+                String name = cursor.getString(0);
+                sContactCache.put(phoneNumber, name);
+                return name;
+            } catch (IndexOutOfBoundsException e) {
+                Log.e(TAG, " Cursor get string error " + e.toString());
+                return null;
+            } finally {
+                cursor.close();
+            }
+        } else {
+            Log.d(TAG, "No contact matched with number:" + phoneNumber);
+            return null;
+        }
+    }
+}
diff --git a/app/src/main/java/net/micode/notes/data/Notes.java b/app/src/main/java/net/micode/notes/data/Notes.java
index 9a9d8d2..f240604 100644
--- a/app/src/main/java/net/micode/notes/data/Notes.java
+++ b/app/src/main/java/net/micode/notes/data/Notes.java
@@ -1,26 +1,40 @@
-package net.micode.notes.data;  // 定义该类所在的包名
+/*
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 
-import android.net.Uri;  // 导入Android的Uri类
+package net.micode.notes.data;
 
-// 定义一个公共类 Notes，用于管理笔记应用中的常量和数据结构
+import android.net.Uri;
 public class Notes {
-    // 定义权限名，用于内容提供者的访问
     public static final String AUTHORITY = "micode_notes";
-    // 定义日志标签名，便于调试
     public static final String TAG = "Notes";
+    public static final int TYPE_NOTE     = 0;
+    public static final int TYPE_FOLDER   = 1;
+    public static final int TYPE_SYSTEM   = 2;
 
-    // 定义笔记类型：普通笔记、文件夹、系统类型
-    public static final int TYPE_NOTE     = 0;   // 普通笔记类型
-    public static final int TYPE_FOLDER   = 1;   // 文件夹类型
-    public static final int TYPE_SYSTEM   = 2;   // 系统类型
+    /**
+     * Following IDs are system folders' identifiers
+     * {@link Notes#ID_ROOT_FOLDER } is default folder
+     * {@link Notes#ID_TEMPARAY_FOLDER } is for notes belonging no folder
+     * {@link Notes#ID_CALL_RECORD_FOLDER} is to store call records
+     */
+    public static final int ID_ROOT_FOLDER = 0;
+    public static final int ID_TEMPARAY_FOLDER = -1;
+    public static final int ID_CALL_RECORD_FOLDER = -2;
+    public static final int ID_TRASH_FOLER = -3;
 
-    // 系统文件夹标识符
-    public static final int ID_ROOT_FOLDER = 0;          // 根文件夹的ID
-    public static final int ID_TEMPARAY_FOLDER = -1;     // 临时文件夹的ID
-    public static final int ID_CALL_RECORD_FOLDER = -2;  // 通话记录文件夹的ID
-    public static final int ID_TRASH_FOLER = -3;         // 垃圾箱文件夹的ID
-
-    // 定义各种Intent额外数据的key
     public static final String INTENT_EXTRA_ALERT_DATE = "net.micode.notes.alert_date";
     public static final String INTENT_EXTRA_BACKGROUND_ID = "net.micode.notes.background_color_id";
     public static final String INTENT_EXTRA_WIDGET_ID = "net.micode.notes.widget_id";
@@ -28,74 +42,238 @@ public class Notes {
     public static final String INTENT_EXTRA_FOLDER_ID = "net.micode.notes.folder_id";
     public static final String INTENT_EXTRA_CALL_DATE = "net.micode.notes.call_date";
 
-    // 定义Widget类型
-    public static final int TYPE_WIDGET_INVALIDE = -1;  // 无效Widget类型
-    public static final int TYPE_WIDGET_2X = 0;         // 2x的Widget类型
-    public static final int TYPE_WIDGET_4X = 1;         // 4x的Widget类型
+    public static final int TYPE_WIDGET_INVALIDE      = -1;
+    public static final int TYPE_WIDGET_2X            = 0;
+    public static final int TYPE_WIDGET_4X            = 1;
 
-    // 定义数据常量类
     public static class DataConstants {
-        // 定义文本笔记类型和通话笔记类型
-        public static final String NOTE = TextNote.CONTENT_ITEM_TYPE;  // 文本笔记类型
-        public static final String CALL_NOTE = CallNote.CONTENT_ITEM_TYPE;  // 通话笔记类型
+        public static final String NOTE = TextNote.CONTENT_ITEM_TYPE;
+        public static final String CALL_NOTE = CallNote.CONTENT_ITEM_TYPE;
     }
 
-    // 定义访问所有笔记和文件夹的Uri
+    /**
+     * Uri to query all notes and folders
+     */
     public static final Uri CONTENT_NOTE_URI = Uri.parse("content://" + AUTHORITY + "/note");
-    // 定义访问数据的Uri
+
+    /**
+     * Uri to query data
+     */
     public static final Uri CONTENT_DATA_URI = Uri.parse("content://" + AUTHORITY + "/data");
 
-    // 定义笔记的列名接口
     public interface NoteColumns {
-        public static final String ID = "_id";  // 每行的唯一ID
-        public static final String PARENT_ID = "parent_id";  // 父ID（文件夹的ID或上级ID）
-        public static final String CREATED_DATE = "created_date";  // 创建日期
-        public static final String MODIFIED_DATE = "modified_date";  // 最后修改日期
-        public static final String ALERTED_DATE = "alert_date";  // 提醒日期
-        public static final String SNIPPET = "snippet";  // 文件夹名称或笔记文本内容
-        public static final String WIDGET_ID = "widget_id";  // Widget的ID
-        public static final String WIDGET_TYPE = "widget_type";  // Widget的类型
-        public static final String BG_COLOR_ID = "bg_color_id";  // 背景颜色ID
-        public static final String HAS_ATTACHMENT = "has_attachment";  // 是否有附件
-        public static final String NOTES_COUNT = "notes_count";  // 文件夹内笔记数量
-        public static final String TYPE = "type";  // 文件类型（笔记或文件夹）
-        public static final String SYNC_ID = "sync_id";  // 同步ID
-        public static final String LOCAL_MODIFIED = "local_modified";  // 是否本地修改
-        public static final String ORIGIN_PARENT_ID = "origin_parent_id";  // 移动前的父ID
-        public static final String GTASK_ID = "gtask_id";  // 任务ID
-        public static final String VERSION = "version";  // 版本号
+        /**
+         * The unique ID for a row
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String ID = "_id";
+
+        /**
+         * The parent's id for note or folder
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String PARENT_ID = "parent_id";
+
+        /**
+         * Created data for note or folder
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String CREATED_DATE = "created_date";
+
+        /**
+         * Latest modified date
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String MODIFIED_DATE = "modified_date";
+
+
+        /**
+         * Alert date
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String ALERTED_DATE = "alert_date";
+
+        /**
+         * Folder's name or text content of note
+         * <P> Type: TEXT </P>
+         */
+        public static final String SNIPPET = "snippet";
+
+        /**
+         * Note's widget id
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String WIDGET_ID = "widget_id";
+
+        /**
+         * Note's widget type
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String WIDGET_TYPE = "widget_type";
+
+        /**
+         * Note's background color's id
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String BG_COLOR_ID = "bg_color_id";
+
+        /**
+         * For text note, it doesn't has attachment, for multi-media
+         * note, it has at least one attachment
+         * <P> Type: INTEGER </P>
+         */
+        public static final String HAS_ATTACHMENT = "has_attachment";
+
+        /**
+         * Folder's count of notes
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String NOTES_COUNT = "notes_count";
+
+        /**
+         * The file type: folder or note
+         * <P> Type: INTEGER </P>
+         */
+        public static final String TYPE = "type";
+
+        /**
+         * The last sync id
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String SYNC_ID = "sync_id";
+
+        /**
+         * Sign to indicate local modified or not
+         * <P> Type: INTEGER </P>
+         */
+        public static final String LOCAL_MODIFIED = "local_modified";
+
+        /**
+         * Original parent id before moving into temporary folder
+         * <P> Type : INTEGER </P>
+         */
+        public static final String ORIGIN_PARENT_ID = "origin_parent_id";
+
+        /**
+         * The gtask id
+         * <P> Type : TEXT </P>
+         */
+        public static final String GTASK_ID = "gtask_id";
+
+        /**
+         * The version code
+         * <P> Type : INTEGER (long) </P>
+         */
+        public static final String VERSION = "version";
     }
 
-    // 定义数据列的接口
     public interface DataColumns {
-        public static final String ID = "_id";  // 数据的唯一ID
-        public static final String MIME_TYPE = "mime_type";  // 数据的MIME类型
-        public static final String NOTE_ID = "note_id";  // 数据所属的笔记ID
-        public static final String CREATED_DATE = "created_date";  // 数据创建日期
-        public static final String MODIFIED_DATE = "modified_date";  // 数据最后修改日期
-        public static final String CONTENT = "content";  // 数据内容
-        public static final String DATA1 = "data1";  // 通用数据列1
-        public static final String DATA2 = "data2";  // 通用数据列2
-        public static final String DATA3 = "data3";  // 通用数据列3
-        public static final String DATA4 = "data4";  // 通用数据列4
-        public static final String DATA5 = "data5";  // 通用数据列5
+        /**
+         * The unique ID for a row
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String ID = "_id";
+
+        /**
+         * The MIME type of the item represented by this row.
+         * <P> Type: Text </P>
+         */
+        public static final String MIME_TYPE = "mime_type";
+
+        /**
+         * The reference id to note that this data belongs to
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String NOTE_ID = "note_id";
+
+        /**
+         * Created data for note or folder
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String CREATED_DATE = "created_date";
+
+        /**
+         * Latest modified date
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String MODIFIED_DATE = "modified_date";
+
+        /**
+         * Data's content
+         * <P> Type: TEXT </P>
+         */
+        public static final String CONTENT = "content";
+
+
+        /**
+         * Generic data column, the meaning is {@link #MIMETYPE} specific, used for
+         * integer data type
+         * <P> Type: INTEGER </P>
+         */
+        public static final String DATA1 = "data1";
+
+        /**
+         * Generic data column, the meaning is {@link #MIMETYPE} specific, used for
+         * integer data type
+         * <P> Type: INTEGER </P>
+         */
+        public static final String DATA2 = "data2";
+
+        /**
+         * Generic data column, the meaning is {@link #MIMETYPE} specific, used for
+         * TEXT data type
+         * <P> Type: TEXT </P>
+         */
+        public static final String DATA3 = "data3";
+
+        /**
+         * Generic data column, the meaning is {@link #MIMETYPE} specific, used for
+         * TEXT data type
+         * <P> Type: TEXT </P>
+         */
+        public static final String DATA4 = "data4";
+
+        /**
+         * Generic data column, the meaning is {@link #MIMETYPE} specific, used for
+         * TEXT data type
+         * <P> Type: TEXT </P>
+         */
+        public static final String DATA5 = "data5";
     }
 
-    // 定义文本笔记类
     public static final class TextNote implements DataColumns {
-        public static final String MODE = DATA1;  // 模式字段：是否为检查列表模式
-        public static final int MODE_CHECK_LIST = 1;  // 检查列表模式
-        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/text_note";  // 内容类型：多个文本笔记
-        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/text_note";  // 内容类型：单个文本笔记
-        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/text_note");  // 文本笔记的访问Uri
+        /**
+         * Mode to indicate the text in check list mode or not
+         * <P> Type: Integer 1:check list mode 0: normal mode </P>
+         */
+        public static final String MODE = DATA1;
+
+        public static final int MODE_CHECK_LIST = 1;
+
+        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/text_note";
+
+        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/text_note";
+
+        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/text_note");
     }
 
-    // 定义通话笔记类
     public static final class CallNote implements DataColumns {
-        public static final String CALL_DATE = DATA1;  // 通话日期字段
-        public static final String PHONE_NUMBER = DATA3;  // 电话号码字段
-        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/call_note";  // 内容类型：多个通话笔记
-        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/call_note";  // 内容类型：单个通话笔记
-        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/call_note");  // 通话笔记的访问Uri
+        /**
+         * Call date for this record
+         * <P> Type: INTEGER (long) </P>
+         */
+        public static final String CALL_DATE = DATA1;
+
+        /**
+         * Phone number for this record
+         * <P> Type: TEXT </P>
+         */
+        public static final String PHONE_NUMBER = DATA3;
+
+        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/call_note";
+
+        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/call_note";
+
+        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/call_note");
     }
 }
diff --git a/app/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java b/app/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java
index cd108a5..ffe5d57 100644
--- a/app/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java
+++ b/app/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java
@@ -1,287 +1,362 @@
-package net.micode.notes.data;  // 包声明
+/*
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 
-import android.content.ContentValues;  // 导入ContentValues类
-import android.content.Context;  // 导入Context类
-import android.database.sqlite.SQLiteDatabase;  // 导入SQLiteDatabase类
-import android.database.sqlite.SQLiteOpenHelper;  // 导入SQLiteOpenHelper类
-import android.util.Log;  // 导入Log类
+package net.micode.notes.data;
+
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.sqlite.SQLiteDatabase;
+import android.database.sqlite.SQLiteOpenHelper;
+import android.util.Log;
+
+import net.micode.notes.data.Notes.DataColumns;
+import net.micode.notes.data.Notes.DataConstants;
+import net.micode.notes.data.Notes.NoteColumns;
 
-import net.micode.notes.data.Notes.DataColumns;  // 导入DataColumns类
-import net.micode.notes.data.Notes.DataConstants;  // 导入DataConstants类
-import net.micode.notes.data.Notes.NoteColumns;  // 导入NoteColumns类
 
-// Notes数据库帮助类
 public class NotesDatabaseHelper extends SQLiteOpenHelper {
-    private static final String DB_NAME = "note.db";  // 定义数据库名称
-    private static final int DB_VERSION = 4;  // 定义数据库版本号
+    private static final String DB_NAME = "note.db";
+
+    private static final int DB_VERSION = 4;
 
-    // 表名接口
     public interface TABLE {
-        public static final String NOTE = "note";  // 笔记表名
-        public static final String DATA = "data";  // 数据表名
+        public static final String NOTE = "note";
+
+        public static final String DATA = "data";
     }
 
-    private static final String TAG = "NotesDatabaseHelper";  // 用于日志输出的TAG
+    private static final String TAG = "NotesDatabaseHelper";
 
-    private static NotesDatabaseHelper mInstance;  // 定义数据库帮助类的实例
+    private static NotesDatabaseHelper mInstance;
 
-    // 创建笔记表的SQL语句
     private static final String CREATE_NOTE_TABLE_SQL =
-            "CREATE TABLE " + TABLE.NOTE + "(" +  // 创建笔记表
-                    NoteColumns.ID + " INTEGER PRIMARY KEY," +  // 笔记ID，主键
-                    NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +  // 父级笔记ID，默认为0
-                    NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +  // 提醒日期，默认为0
-                    NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +  // 背景色ID，默认为0
-                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +  // 创建日期，默认为当前时间戳
-                    NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +  // 是否有附件，默认为0
-                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +  // 修改日期，默认为当前时间戳
-                    NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +  // 笔记数量，默认为0
-                    NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +  // 笔记摘要，默认为空字符串
-                    NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +  // 笔记类型，默认为0
-                    NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +  // 小部件ID，默认为0
-                    NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +  // 小部件类型，默认为-1
-                    NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +  // 同步ID，默认为0
-                    NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +  // 本地修改标志，默认为0
-                    NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +  // 原父级ID，默认为0
-                    NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +  // GTASK ID，默认为空字符串
-                    NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +  // 笔记版本号，默认为0
-                    ")";  // 结束创建表的SQL语句
-    // 创建触发器SQL
-    // 创建数据表的SQL语句
-    private static final String CREATE_DATA_TABLE_SQL =// 创建触发器SQL
-            "CREATE TABLE " + TABLE.DATA + "(" +  // 创建数据表
-                    DataColumns.ID + " INTEGER PRIMARY KEY," +  // 数据ID，主键
-                    DataColumns.MIME_TYPE + " TEXT NOT NULL," +  // MIME类型
-                    DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +  // 笔记ID，默认为0
-                    NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +  // 创建日期，默认为当前时间戳
-                    NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +  // 修改日期，默认为当前时间戳
-                    DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +  // 内容，默认为空字符串
-                    DataColumns.DATA1 + " INTEGER," +  // 数据字段1
-                    DataColumns.DATA2 + " INTEGER," +  // 数据字段2
-                    DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +  // 数据字段3，默认为空字符串
-                    DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +  // 数据字段4，默认为空字符串
-                    DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +  // 数据字段5，默认为空字符串
-                    ")";  // 结束创建数据表的SQL语句// 创建触发器SQL
-    // 创建触发器SQL
-    // 创建数据表的NOTE_ID索引// 创建触发器SQL
-    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =// 创建触发器SQL
-            "CREATE INDEX IF NOT EXISTS note_id_index ON " +// 创建触发器SQL
-                    TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";  // 创建数据表的NOTE_ID索引
-    // 创建触发器SQL
-    // 创建触发器：更新笔记的父级ID时增加父文件夹的笔记数// 创建触发器SQL
-    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER increase_folder_count_on_update " +// 创建触发器SQL
-                    " AFTER UPDATE OF " + eColumns.PARENT_ID + " ON " + TABLE.NOTE +// 创建触发器SQL
-                    " BEGIN " +// 创建触发器SQL
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL// 创建触发器SQL// 创建触发器SQL
-                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +// 创建触发器SQL// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-    // 创建触发器SQL
-    // 创建触发器：更新笔记的父级ID时减少父文件夹的笔记数
-    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER decrease_folder_count_on_update " +// 创建触发器SQL
-                    " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +// 创建触发器SQL
-                    " BEGIN " +// 创建触发器SQL// 创建触发器SQL
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL
-                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +// 创建触发器SQL
-                    "  AND " + NoteColumns.NOTES_COUNT + ">0" + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：插入笔记时增加父文件夹的笔记数
-    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER increase_folder_count_on_insert " +// 创建触发器SQL
-                    " AFTER INSERT ON " + TABLE.NOTE +// 创建触发器SQL
-                    " BEGIN " +// 创建触发器SQL
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL
-                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：删除笔记时减少父文件夹的笔记数
-    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER decrease_folder_count_on_delete " +// 创建触发器SQL
-                    " AFTER DELETE ON " + TABLE.NOTE +// 创建触发器SQL
-                    " BEGIN " +// 创建触发器SQL
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL
-                    "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +// 创建触发器SQL
-                    "  AND " + NoteColumns.NOTES_COUNT + ">0;" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：插入数据时更新笔记的摘要
-    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER update_note_content_on_insert " +// 创建触发器SQL
-                    " AFTER INSERT ON " + TABLE.DATA +// 创建触发器SQL
-                    " WHEN new." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +// 创建触发器SQL
-                    " BEGIN" +// 创建触发器SQL
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL
-                    "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：更新数据时更新笔记的摘要
-    private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER update_note_content_on_update " +// 创建触发器SQL// 创建触发器SQL
-                    " AFTER UPDATE ON " + TABLE.DATA +
-                    " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +// 创建触发器SQL
-                    " BEGIN" +// 创建触发器SQL
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL
-                    "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：删除数据时更新笔记的摘要
-    private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER update_note_content_on_delete " +// 创建触发器SQL
-                    " AFTER delete ON " + TABLE.DATA +// 创建触发器SQL
-                    " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +// 创建触发器SQL
-                    " BEGIN" +
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL
-                    "   SET " + NoteColumns.SNIPPET + "=''" +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：删除笔记时删除相关的数据
-    private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER delete_data_on_delete " +// 创建触发器SQL
-                    " AFTER DELETE ON " + TABLE.NOTE +// 创建触发器SQL
-                    " BEGIN" +// 创建触发器SQL
-                    "  DELETE FROM " + TABLE.DATA +// 创建触发器SQL
-                    "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：删除文件夹时删除该文件夹中的所有笔记
-    private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER folder_delete_notes_on_delete " +// 创建触发器SQL
-                    " AFTER DELETE ON " + TABLE.NOTE +// 创建触发器SQL
-                    " BEGIN" +// 创建触发器SQL
-                    "  DELETE FROM " + TABLE.NOTE +// 创建触发器SQL
-                    "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 创建触发器：移动文件夹到回收站时移动所有笔记到回收站
-    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =// 创建触发器SQL
-            "CREATE TRIGGER folder_move_notes_on_trash " +// 创建触发器SQL
-                    " AFTER UPDATE ON " + TABLE.NOTE +// 创建触发器SQL
-                    " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +// 创建触发器SQL
-                    " BEGIN" +// 创建触发器SQL
-                    "  UPDATE " + TABLE.NOTE +// 创建触发器SQL
-                    "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +// 创建触发器SQL
-                    "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +// 创建触发器SQL
-                    " END";  // 创建触发器SQL
-
-    // 构造函数，初始化数据库帮助类
+        "CREATE TABLE " + TABLE.NOTE + "(" +
+            NoteColumns.ID + " INTEGER PRIMARY KEY," +
+            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +
+            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +
+            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +
+            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +
+        ")";
+
+    private static final String CREATE_DATA_TABLE_SQL =
+        "CREATE TABLE " + TABLE.DATA + "(" +
+            DataColumns.ID + " INTEGER PRIMARY KEY," +
+            DataColumns.MIME_TYPE + " TEXT NOT NULL," +
+            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA1 + " INTEGER," +
+            DataColumns.DATA2 + " INTEGER," +
+            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
+        ")";
+
+    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
+        "CREATE INDEX IF NOT EXISTS note_id_index ON " +
+        TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";
+
+    /**
+     * Increase folder's note count when move note to the folder
+     */
+    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
+        "CREATE TRIGGER increase_folder_count_on_update "+
+        " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
+        " BEGIN " +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
+        "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
+        " END";
+
+    /**
+     * Decrease folder's note count when move note from folder
+     */
+    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
+        "CREATE TRIGGER decrease_folder_count_on_update " +
+        " AFTER UPDATE OF " + NoteColumns.PARENT_ID + " ON " + TABLE.NOTE +
+        " BEGIN " +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
+        "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
+        "  AND " + NoteColumns.NOTES_COUNT + ">0" + ";" +
+        " END";
+
+    /**
+     * Increase folder's note count when insert new note to the folder
+     */
+    private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =
+        "CREATE TRIGGER increase_folder_count_on_insert " +
+        " AFTER INSERT ON " + TABLE.NOTE +
+        " BEGIN " +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" +
+        "  WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" +
+        " END";
+
+    /**
+     * Decrease folder's note count when delete note from the folder
+     */
+    private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
+        "CREATE TRIGGER decrease_folder_count_on_delete " +
+        " AFTER DELETE ON " + TABLE.NOTE +
+        " BEGIN " +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" +
+        "  WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID +
+        "  AND " + NoteColumns.NOTES_COUNT + ">0;" +
+        " END";
+
+    /**
+     * Update note's content when insert data with type {@link DataConstants#NOTE}
+     */
+    private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
+        "CREATE TRIGGER update_note_content_on_insert " +
+        " AFTER INSERT ON " + TABLE.DATA +
+        " WHEN new." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
+        " BEGIN" +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
+        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
+        " END";
+
+    /**
+     * Update note's content when data with {@link DataConstants#NOTE} type has changed
+     */
+    private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
+        "CREATE TRIGGER update_note_content_on_update " +
+        " AFTER UPDATE ON " + TABLE.DATA +
+        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
+        " BEGIN" +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT +
+        "  WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" +
+        " END";
+
+    /**
+     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
+     */
+    private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
+        "CREATE TRIGGER update_note_content_on_delete " +
+        " AFTER delete ON " + TABLE.DATA +
+        " WHEN old." + DataColumns.MIME_TYPE + "='" + DataConstants.NOTE + "'" +
+        " BEGIN" +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.SNIPPET + "=''" +
+        "  WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" +
+        " END";
+
+    /**
+     * Delete datas belong to note which has been deleted
+     */
+    private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
+        "CREATE TRIGGER delete_data_on_delete " +
+        " AFTER DELETE ON " + TABLE.NOTE +
+        " BEGIN" +
+        "  DELETE FROM " + TABLE.DATA +
+        "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +
+        " END";
+
+    /**
+     * Delete notes belong to folder which has been deleted
+     */
+    private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
+        "CREATE TRIGGER folder_delete_notes_on_delete " +
+        " AFTER DELETE ON " + TABLE.NOTE +
+        " BEGIN" +
+        "  DELETE FROM " + TABLE.NOTE +
+        "   WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
+        " END";
+
+    /**
+     * Move notes belong to folder which has been moved to trash folder
+     */
+    private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
+        "CREATE TRIGGER folder_move_notes_on_trash " +
+        " AFTER UPDATE ON " + TABLE.NOTE +
+        " WHEN new." + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
+        " BEGIN" +
+        "  UPDATE " + TABLE.NOTE +
+        "   SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER +
+        "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
+        " END";
+
     public NotesDatabaseHelper(Context context) {
-        super(context, DB_NAME, null, DB_VERSION);  // 调用父类的构造函数，指定数据库名称和版本
+        super(context, DB_NAME, null, DB_VERSION);
     }
 
-    // 创建笔记表
     public void createNoteTable(SQLiteDatabase db) {
-        db.execSQL(CREATE_NOTE_TABLE_SQL);  // 执行创建笔记表的SQL语句
-        reCreateNoteTableTriggers(db);  // 创建触发器
+        db.execSQL(CREATE_NOTE_TABLE_SQL);
+        reCreateNoteTableTriggers(db);
+        createSystemFolder(db);
+        Log.d(TAG, "note table has been created");
+    }
+
+    private void reCreateNoteTableTriggers(SQLiteDatabase db) {
+        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
+        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_update");
+        db.execSQL("DROP TRIGGER IF EXISTS decrease_folder_count_on_delete");
+        db.execSQL("DROP TRIGGER IF EXISTS delete_data_on_delete");
+        db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_insert");
+        db.execSQL("DROP TRIGGER IF EXISTS folder_delete_notes_on_delete");
+        db.execSQL("DROP TRIGGER IF EXISTS folder_move_notes_on_trash");
+
+        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
+        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);
+        db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER);
+        db.execSQL(NOTE_DELETE_DATA_ON_DELETE_TRIGGER);
+        db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER);
+        db.execSQL(FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER);
+        db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);
+    }
+
+    private void createSystemFolder(SQLiteDatabase db) {
+        ContentValues values = new ContentValues();
+
+        /**
+         * call record foler for call notes
+         */
+        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
+
+        /**
+         * root folder which is default folder
+         */
+        values.clear();
+        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
+
+        /**
+         * temporary folder which is used for moving note
+         */
+        values.clear();
+        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
+
+        /**
+         * create trash folder
+         */
+        values.clear();
+        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
     }
 
-    // 创建数据表
     public void createDataTable(SQLiteDatabase db) {
-        db.execSQL(CREATE_DATA_TABLE_SQL);  // 执行创建数据表的SQL语句
-        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);  // 创建数据表的索引
-        Log.d(TAG, "data table has been created");  // 打印日志
+        db.execSQL(CREATE_DATA_TABLE_SQL);
+        reCreateDataTableTriggers(db);
+        db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
+        Log.d(TAG, "data table has been created");
     }
 
-    // 执行数据库创建操作
-    @Override
-    public void onCreate(SQLiteDatabase db) {
-        createNoteTable(db);  // 创建笔记表
-        createDataTable(db);  // 创建数据表
+    private void reCreateDataTableTriggers(SQLiteDatabase db) {
+        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
+        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_update");
+        db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_delete");
+
+        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER);
+        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER);
+        db.execSQL(DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER);
     }
-    @Override
-    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
-        Log.d(TAG, "onUpgrade: " + oldVersion + " --> " + newVersion);  // 打印日志
 
-        // 根据版本号升级数据库
-        if (oldVersion == 1) {
-            db.execSQL(CREATE_DATA_TABLE_SQL);  // 创建数据表
-            db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);  // 创建索引
-            db.execSQL(NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);  // 创建触发器
-            db.execSQL(NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER);  // 创建触发器
-        }
-        if (oldVersion <= 3) {
-            createNoteTable(db);  // 创建笔记表
-            reCreateNoteTableTriggers(db);  // 创建触发器
+    static synchronized NotesDatabaseHelper getInstance(Context context) {
+        if (mInstance == null) {
+            mInstance = new NotesDatabaseHelper(context);
         }
+        return mInstance;
     }
-    // 执行数据库升级操作
+
+    @Override
+    public void onCreate(SQLiteDatabase db) {
+        createNoteTable(db);
+        createDataTable(db);
+    }
+
     @Override
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
-        boolean reCreateTriggers = false;  // 是否需要重新创建触发器的标志
-        boolean skipV2 = false;  // 是否跳过V2升级的标志
+        boolean reCreateTriggers = false;
+        boolean skipV2 = false;
 
-        // 如果当前数据库版本是1，进行从V1升级到V2的操作
         if (oldVersion == 1) {
-            upgradeToV2(db);  // 执行V1到V2的升级
-            skipV2 = true;  // 跳过V2到V3的升级
-            oldVersion++;  // 更新数据库版本为2
+            upgradeToV2(db);
+            skipV2 = true; // this upgrade including the upgrade from v2 to v3
+            oldVersion++;
         }
 
-        // 如果当前数据库版本是2且没有跳过V2升级
         if (oldVersion == 2 && !skipV2) {
-            upgradeToV3(db);  // 执行V2到V3的升级
-            reCreateTriggers = true;  // 标记需要重新创建触发器
-            oldVersion++;  // 更新数据库版本为3
+            upgradeToV3(db);
+            reCreateTriggers = true;
+            oldVersion++;
         }
 
-        // 如果当前数据库版本是3，执行V3到V4的升级
         if (oldVersion == 3) {
-            upgradeToV4(db);  // 执行V3到V4的升级
-            oldVersion++;  // 更新数据库版本为4
-        }// 添加VERSION列，默认为0
+            upgradeToV4(db);
+            oldVersion++;
+        }
 
-        // 如果需要重新创建触发器，执行重新创建触发器的操作
         if (reCreateTriggers) {
-            reCreateNoteTableTriggers(db);  // 重新创建笔记表的触发器
-            reCreateDataTableTriggers(db);  // 重新创建数据表的触发器
+            reCreateNoteTableTriggers(db);
+            reCreateDataTableTriggers(db);
         }
 
-        // 如果升级后的版本不等于目标版本，抛出异常
         if (oldVersion != newVersion) {
-            throw new IllegalStateException("Upgrade notes database to version " + newVersion// 添加VERSION列，默认为0
-                    + " fails");  // 升级失败抛出异常
-        }// 添加VERSION列，默认为0
-    }// 添加VERSION列，默认为0
-    // 添加VERSION列，默认为0
-    // 从V1升级到V2
+            throw new IllegalStateException("Upgrade notes database to version " + newVersion
+                    + "fails");
+        }
+    }
+
     private void upgradeToV2(SQLiteDatabase db) {
-        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);  // 删除笔记表（如果存在）
-        db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);  // 删除数据表（如果存在）
-        createNoteTable(db);  // 重新创建笔记表
-        createDataTable(db);  // 重新创建数据表
-    }// 添加VERSION列，默认为0
-    // 添加VERSION列，默认为0
-    // 从V2升级到V3
+        db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
+        db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
+        createNoteTable(db);
+        createDataTable(db);
+    }
+
     private void upgradeToV3(SQLiteDatabase db) {
-        // 删除不再使用的触发器
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_insert");  // 删除插入时更新时间触发器
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_delete");  // 删除删除时更新时间触发器
-        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_update");  // 删除更新时更新时间触发器
-        // 在笔记表中添加一个新的列，用于存储gtask ID
+        // drop unused triggers
+        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_insert");
+        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_delete");
+        db.execSQL("DROP TRIGGER IF EXISTS update_note_modified_date_on_update");
+        // add a column for gtask id
         db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
-                + " TEXT NOT NULL DEFAULT ''");  // 添加GTASK_ID列，默认为空字符串
-        // 在笔记表中添加一个垃圾系统文件夹
-        ContentValues values = new ContentValues();  // 创建一个ContentValues对象
-        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);  // 设置垃圾文件夹ID
-        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);  // 设置文件夹类型为系统文件夹
-        db.insert(TABLE.NOTE, null, values);  // 插入新的垃圾文件夹记录
-    }// 添加VERSION列，默认为0
-    // 添加VERSION列，默认为0
-    // 从V3升级到V4
+                + " TEXT NOT NULL DEFAULT ''");
+        // add a trash system folder
+        ContentValues values = new ContentValues();
+        values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
+    }
+
     private void upgradeToV4(SQLiteDatabase db) {
-        // 在笔记表中添加一个新的列，用于存储版本号
         db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
-                + " INTEGER NOT NULL DEFAULT 0");  // 添加VERSION列，默认为0
-    }// 添加VERSION列，默认为0
-// 添加VERSION列，默认为0
-// 添加VERSION列，默认为0
-}// 添加VERSION列，默认为0
-// 添加VERSION列，默认为0
\ No newline at end of file
+                + " INTEGER NOT NULL DEFAULT 0");
+    }
+}
diff --git a/app/src/main/java/net/micode/notes/data/NotesProvider.java b/app/src/main/java/net/micode/notes/data/NotesProvider.java
index 1e3e6a7..edb0a60 100644
--- a/app/src/main/java/net/micode/notes/data/NotesProvider.java
+++ b/app/src/main/java/net/micode/notes/data/NotesProvider.java
@@ -1,229 +1,305 @@
 /*
  * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
+ *
  * Licensed under the Apache License, Version 2.0 (the "License");
- * See LICENSE file for full license details.
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
-package net.micode.notes.data;//导入
-
-import android.app.SearchManager;//导入
-import android.content.ContentProvider;//导入
-import android.content.ContentUris;//导入
-import android.content.ContentValues;//导入
-import android.content.Intent;//导入
-import android.content.UriMatcher;//导入
-import android.database.Cursor;//导入
-import android.database.sqlite.SQLiteDatabase;//导入
-import android.net.Uri;//导入
-import android.text.TextUtils;//导入
-import android.util.Log;//导入
-//导入
-import net.micode.notes.R;//导入
-import net.micode.notes.data.Notes.DataColumns;//导入
-import net.micode.notes.data.Notes.NoteColumns;//导入
-import net.micode.notes.data.NotesDatabaseHelper.TABLE;//导入
-
-public class NotesProvider extends ContentProvider {//导入
-
-    // 日志标签，用于日志输出
-    private static final String TAG = "NotesProvider";//导入
-
-    // Uri匹配器，负责匹配传入的Uri
-    private static final UriMatcher mMatcher;// 插入方法
-
-    // 数据库帮助类对象
-    private NotesDatabaseHelper mHelper;// 插入方法
-
-    // 常量定义：匹配不同Uri
-    private static final int URI_NOTE            = 1; // 匹配整个笔记表// 常量定义：匹配不同Uri
-    private static final int URI_NOTE_ITEM       = 2; // 匹配单个笔记项// 常量定义：匹配不同Uri
-    private static final int URI_DATA            = 3; // 匹配数据表// 常量定义：匹配不同Uri
-    private static final int URI_DATA_ITEM       = 4; // 匹配单个数据项// 常量定义：匹配不同Uri
-    private static final int URI_SEARCH          = 5; // 匹配搜索功能// 常量定义：匹配不同Uri
-    private static final int URI_SEARCH_SUGGEST  = 6; // 匹配搜索建议// 常量定义：匹配不同Uri
+package net.micode.notes.data;
+
+
+import android.app.SearchManager;
+import android.content.ContentProvider;
+import android.content.ContentUris;
+import android.content.ContentValues;
+import android.content.Intent;
+import android.content.UriMatcher;
+import android.database.Cursor;
+import android.database.sqlite.SQLiteDatabase;
+import android.net.Uri;
+import android.text.TextUtils;
+import android.util.Log;
+
+import net.micode.notes.R;
+import net.micode.notes.data.Notes.DataColumns;
+import net.micode.notes.data.Notes.NoteColumns;
+import net.micode.notes.data.NotesDatabaseHelper.TABLE;
+
+
+public class NotesProvider extends ContentProvider {
+    private static final UriMatcher mMatcher;
+
+    private NotesDatabaseHelper mHelper;
+
+    private static final String TAG = "NotesProvider";
+
+    private static final int URI_NOTE            = 1;
+    private static final int URI_NOTE_ITEM       = 2;
+    private static final int URI_DATA            = 3;
+    private static final int URI_DATA_ITEM       = 4;
+
+    private static final int URI_SEARCH          = 5;
+    private static final int URI_SEARCH_SUGGEST  = 6;
 
     static {
-        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);// 常量定义：匹配不同Uri
-        mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE); // 匹配笔记表Uri
-        mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM); // 匹配单个笔记
-        mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA); // 匹配数据表Uri
-        mMatcher.addURI(Notes.AUTHORITY, "data/#", URI_DATA_ITEM); // 匹配单个数据项
-        mMatcher.addURI(Notes.AUTHORITY, "search", URI_SEARCH); // 匹配搜索功能
-        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY, URI_SEARCH_SUGGEST); // 匹配搜索建议
-        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY + "/*", URI_SEARCH_SUGGEST); // 带参数的搜索建议
+        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
+        mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE);
+        mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM);
+        mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA);
+        mMatcher.addURI(Notes.AUTHORITY, "data/#", URI_DATA_ITEM);
+        mMatcher.addURI(Notes.AUTHORITY, "search", URI_SEARCH);
+        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY, URI_SEARCH_SUGGEST);
+        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY + "/*", URI_SEARCH_SUGGEST);
     }
 
-    // 查询笔记表的列，去除换行符并用于搜索建议结果显示
+    /**
+     * x'0A' represents the '\n' character in sqlite. For title and content in the search result,
+     * we will trim '\n' and white space in order to show more information.
+     */
     private static final String NOTES_SEARCH_PROJECTION = NoteColumns.ID + ","
-            + NoteColumns.ID + " AS " + SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA + ","
-            + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_1 + ","// 常量定义：匹配不同Uri
-            + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_2 + ","// 常量定义：匹配不同Uri
-            + R.drawable.search_result + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1 + ","// 常量定义：匹配不同Uri
-            + "'" + Intent.ACTION_VIEW + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_ACTION + ","// 常量定义：匹配不同Uri
-            + "'" + Notes.TextNote.CONTENT_TYPE + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_DATA;// 常量定义：匹配不同Uri
-
-    // SQL查询：模糊搜索笔记内容
+        + NoteColumns.ID + " AS " + SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA + ","
+        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_1 + ","
+        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_2 + ","
+        + R.drawable.search_result + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1 + ","
+        + "'" + Intent.ACTION_VIEW + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_ACTION + ","
+        + "'" + Notes.TextNote.CONTENT_TYPE + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_DATA;
+
     private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION
-            + " FROM " + TABLE.NOTE // SQL查询：模糊搜索笔记内容
-            + " WHERE " + NoteColumns.SNIPPET + " LIKE ?" // SQL查询：模糊搜索笔记内容
-            + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER // SQL查询：模糊搜索笔记内容
-            + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE; // SQL查询：模糊搜索笔记内容
+        + " FROM " + TABLE.NOTE
+        + " WHERE " + NoteColumns.SNIPPET + " LIKE ?"
+        + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
+        + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;
 
-    // 初始化ContentProvider时调用
     @Override
-    public boolean onCreate() { // SQL查询：模糊搜索笔记内容
-        mHelper = NotesDatabaseHelper.getInstance(getContext()); // 获取数据库帮助类实例
-        return true; // SQL查询：模糊搜索笔记内容
-    } // SQL查询：模糊搜索笔记内容
+    public boolean onCreate() {
+        mHelper = NotesDatabaseHelper.getInstance(getContext());
+        return true;
+    }
 
-    /**
-     * 查询方法：根据Uri执行相应的查询操作
-     */
     @Override
-    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {// 插入方法
-        Cursor c = null;// 插入方法
-        SQLiteDatabase db = mHelper.getReadableDatabase(); // 获取可读数据库
-        String id = null;// 插入方法
+    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
+            String sortOrder) {
+        Cursor c = null;
+        SQLiteDatabase db = mHelper.getReadableDatabase();
+        String id = null;
+        switch (mMatcher.match(uri)) {
+            case URI_NOTE:
+                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
+                        sortOrder);
+                break;
+            case URI_NOTE_ITEM:
+                id = uri.getPathSegments().get(1);
+                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id
+                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
+                break;
+            case URI_DATA:
+                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
+                        sortOrder);
+                break;
+            case URI_DATA_ITEM:
+                id = uri.getPathSegments().get(1);
+                c = db.query(TABLE.DATA, projection, DataColumns.ID + "=" + id
+                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
+                break;
+            case URI_SEARCH:
+            case URI_SEARCH_SUGGEST:
+                if (sortOrder != null || projection != null) {
+                    throw new IllegalArgumentException(
+                            "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
+                }
+
+                String searchString = null;
+                if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
+                    if (uri.getPathSegments().size() > 1) {
+                        searchString = uri.getPathSegments().get(1);
+                    }
+                } else {
+                    searchString = uri.getQueryParameter("pattern");
+                }
+
+                if (TextUtils.isEmpty(searchString)) {
+                    return null;
+                }
+
+                try {
+                    searchString = String.format("%%%s%%", searchString);
+                    c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY,
+                            new String[] { searchString });
+                } catch (IllegalStateException ex) {
+                    Log.e(TAG, "got exception: " + ex.toString());
+                }
+                break;
+            default:
+                throw new IllegalArgumentException("Unknown URI " + uri);
+        }
+        if (c != null) {
+            c.setNotificationUri(getContext().getContentResolver(), uri);
+        }
+        return c;
+    }
 
+    @Override
+    public Uri insert(Uri uri, ContentValues values) {
+        SQLiteDatabase db = mHelper.getWritableDatabase();
+        long dataId = 0, noteId = 0, insertedId = 0;
         switch (mMatcher.match(uri)) {
             case URI_NOTE:
-                // 查询笔记表
-                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null, sortOrder);// 插入方法
-                break;// 插入方法
-            // SQL查询：模糊搜索笔记内容
-            case URI_NOTE_ITEM:// 插入方法
-                // 查询特定的笔记
-                id = uri.getPathSegments().get(1);// 插入方法
-                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs, null, null, sortOrder);
-                break; // SQL查询：模糊搜索笔记内容
-            // SQL查询：模糊搜索笔记内容
-            case URI_DATA: // SQL查询：模糊搜索笔记内容
-                // 查询数据表
-                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null, sortOrder);
-                break; // SQL查询：模糊搜索笔记内容
-
-            case URI_DATA_ITEM: // SQL查询：模糊搜索笔记内容
-                // 查询特定的数据项
-                id = uri.getPathSegments().get(1); // SQL查询：模糊搜索笔记内容
-                c = db.query(TABLE.DATA, projection, DataColumns.ID + "=" + id + parseSelection(selection), selectionArgs, null, null, sortOrder);
-                break; // SQL查询：模糊搜索笔记内容
-
-            case URI_SEARCH: // SQL查询：模糊搜索笔记内容
-            case URI_SEARCH_SUGGEST: // SQL查询：模糊搜索笔记内容
-                // 执行搜索查询
-                if (sortOrder != null || projection != null) { // SQL查询：模糊搜索笔记内容
-                    throw new IllegalArgumentException("Invalid query parameters for search"); // SQL查询：模糊搜索笔记内容
-                } // SQL查询：模糊搜索笔记内容
-
-                String searchString = null; // SQL查询：模糊搜索笔记内容
-
-                if (mMatcher.match(uri) == URI_SEARCH_SUGGEST && uri.getPathSegments().size() > 1) { // SQL查询：模糊搜索笔记内容
-                    searchString = uri.getPathSegments().get(1); // SQL查询：模糊搜索笔记内容
-                } else { // SQL查询：模糊搜索笔记内容
-                    searchString = uri.getQueryParameter("pattern"); // SQL查询：模糊搜索笔记内容
-                } // SQL查询：模糊搜索笔记内容
-
-                if (TextUtils.isEmpty(searchString)) { // SQL查询：模糊搜索笔记内容
-                    return null; // SQL查询：模糊搜索笔记内容
-                } // SQL查询：模糊搜索笔记内容
-
-                try { // SQL查询：模糊搜索笔记内容
-                    searchString = String.format("%%%s%%", searchString); // SQL查询：模糊搜索笔记内容
-                    c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY, new String[] { searchString }); // SQL查询：模糊搜索笔记内容
-                } catch (IllegalStateException ex) { // SQL查询：模糊搜索笔记内容
-                    Log.e(TAG, "Exception during search query: " + ex.toString()); // SQL查询：模糊搜索笔记内容
-                } // SQL查询：模糊搜索笔记内容
-                break; // SQL查询：模糊搜索笔记内容
-
-            default: // SQL查询：模糊搜索笔记内容
-                throw new IllegalArgumentException("Unknown URI: " + uri); // SQL查询：模糊搜索笔记内容
-        } // SQL查询：模糊搜索笔记内容
-        // SQL查询：模糊搜索笔记内容
-        if (c != null) { // SQL查询：模糊搜索笔记内容
-            c.setNotificationUri(getContext().getContentResolver(), uri); // SQL查询：模糊搜索笔记内容
-        } // SQL查询：模糊搜索笔记内容
-
-        return c; // SQL查询：模糊搜索笔记内容
-    } // SQL查询：模糊搜索笔记内容
-
-    // 插入方法
+                insertedId = noteId = db.insert(TABLE.NOTE, null, values);
+                break;
+            case URI_DATA:
+                if (values.containsKey(DataColumns.NOTE_ID)) {
+                    noteId = values.getAsLong(DataColumns.NOTE_ID);
+                } else {
+                    Log.d(TAG, "Wrong data format without note id:" + values.toString());
+                }
+                insertedId = dataId = db.insert(TABLE.DATA, null, values);
+                break;
+            default:
+                throw new IllegalArgumentException("Unknown URI " + uri);
+        }
+        // Notify the note uri
+        if (noteId > 0) {
+            getContext().getContentResolver().notifyChange(
+                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
+        }
+
+        // Notify the data uri
+        if (dataId > 0) {
+            getContext().getContentResolver().notifyChange(
+                    ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
+        }
+
+        return ContentUris.withAppendedId(uri, insertedId);
+    }
+
     @Override
-    public Uri insert(Uri uri, ContentValues values) {// 插入方法
-        SQLiteDatabase db = mHelper.getWritableDatabase();// 插入方法
-        long insertedId = 0;// 插入方法
-        switch (mMatcher.match(uri)) {// 插入方法
-            case URI_NOTE:// 插入方法
-                insertedId = db.insert(TABLE.NOTE, null, values); // 插入到笔记表
-                break;// 插入方法
-
-            case URI_DATA:// 插入方法
-                insertedId = db.insert(TABLE.DATA, null, values); // 插入到数据表
-                break;// 插入方法
-
-            default:// 插入方法
-                throw new IllegalArgumentException("Unknown URI: " + uri);// 插入方法
-        }// 插入方法
-
-        getContext().getContentResolver().notifyChange(uri, null); // 通知数据变更
-        return ContentUris.withAppendedId(uri, insertedId);// 插入方法
-    } // SQL查询：模糊搜索笔记内容
-
-    // 删除方法
+    public int delete(Uri uri, String selection, String[] selectionArgs) {
+        int count = 0;
+        String id = null;
+        SQLiteDatabase db = mHelper.getWritableDatabase();
+        boolean deleteData = false;
+        switch (mMatcher.match(uri)) {
+            case URI_NOTE:
+                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 ";
+                count = db.delete(TABLE.NOTE, selection, selectionArgs);
+                break;
+            case URI_NOTE_ITEM:
+                id = uri.getPathSegments().get(1);
+                /**
+                 * ID that smaller than 0 is system folder which is not allowed to
+                 * trash
+                 */
+                long noteId = Long.valueOf(id);
+                if (noteId <= 0) {
+                    break;
+                }
+                count = db.delete(TABLE.NOTE,
+                        NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
+                break;
+            case URI_DATA:
+                count = db.delete(TABLE.DATA, selection, selectionArgs);
+                deleteData = true;
+                break;
+            case URI_DATA_ITEM:
+                id = uri.getPathSegments().get(1);
+                count = db.delete(TABLE.DATA,
+                        DataColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
+                deleteData = true;
+                break;
+            default:
+                throw new IllegalArgumentException("Unknown URI " + uri);
+        }
+        if (count > 0) {
+            if (deleteData) {
+                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
+            }
+            getContext().getContentResolver().notifyChange(uri, null);
+        }
+        return count;
+    }
+
     @Override
-    public int delete(Uri uri, String selection, String[] selectionArgs) { // SQL查询：模糊搜索笔记内容
-        SQLiteDatabase db = mHelper.getWritableDatabase(); // SQL查询：模糊搜索笔记内容
-        int count = 0; // SQL查询：模糊搜索笔记内容
-
-        switch (mMatcher.match(uri)) { // SQL查询：模糊搜索笔记内容
-            case URI_NOTE: // SQL查询：模糊搜索笔记内容
-                count = db.delete(TABLE.NOTE, selection, selectionArgs); // SQL查询：模糊搜索笔记内容
-                break; // SQL查询：模糊搜索笔记内容
-            // SQL查询：模糊搜索笔记内容
-            case URI_NOTE_ITEM: // SQL查询：模糊搜索笔记内容
-                count = db.delete(TABLE.NOTE, NoteColumns.ID  // SQL查询：模糊搜索笔记内容+ "=" + id + parseSelection(selection), selectionArgs);
-                String id = uri.getPathSegments().get(1);
-              //  count = db.delete(TABLE.NOTE, NoteColumns.ID  // SQL查询：模糊搜索笔记内容+ "=" + id + parseSelection(selection), selectionArgs);
-                count = db.delete(TABLE.NOTE, NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);// SQL查询：模糊搜索笔记内容
-                break;// SQL查询：模糊搜索笔记内容
-
-            default:// SQL查询：模糊搜索笔记内容
-                throw new IllegalArgumentException("Unknown URI: " + uri);// SQL查询：模糊搜索笔记内容
-        }// SQL查询：模糊搜索笔记内容
-
-        if (count > 0) {// SQL查询：模糊搜索笔记内容
-            getContext().getContentResolver().notifyChange(uri, null); // 数据变更通知
-        }// SQL查询：模糊搜索笔记内容
-        return count;// SQL查询：模糊搜索笔记内容
-    }// SQL查询：模糊搜索笔记内容
-
-    // 更新方法
-    @Override// SQL查询：模糊搜索笔记内容
-    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {// SQL查询：模糊搜索笔记内容
-        SQLiteDatabase db = mHelper.getWritableDatabase();// SQL查询：模糊搜索笔记内容
-        int count = 0;// SQL查询：模糊搜索笔记内容
-// SQL查询：模糊搜索笔记内容
-        switch (mMatcher.match(uri)) {// SQL查询：模糊搜索笔记内容
-            case URI_NOTE:// SQL查询：模糊搜索笔记内容
-                count = db.update(TABLE.NOTE, values, selection, selectionArgs);// SQL查询：模糊搜索笔记内容
-                break;// SQL查询：模糊搜索笔记内容
-
-            default:// SQL查询：模糊搜索笔记内容
-                throw new IllegalArgumentException("Unknown URI: " + uri);// SQL查询：模糊搜索笔记内容
-        }// SQL查询：模糊搜索笔记内容
-
-        if (count > 0) {// SQL查询：模糊搜索笔记内容
-            getContext().getContentResolver().notifyChange(uri, null);// SQL查询：模糊搜索笔记内容
-        }// SQL查询：模糊搜索笔记内容
-        return count;// SQL查询：模糊搜索笔记内容
-    }// SQL查询：模糊搜索笔记内容
-
-    // 辅助方法：解析selection条件
+    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
+        int count = 0;
+        String id = null;
+        SQLiteDatabase db = mHelper.getWritableDatabase();
+        boolean updateData = false;
+        switch (mMatcher.match(uri)) {
+            case URI_NOTE:
+                increaseNoteVersion(-1, selection, selectionArgs);
+                count = db.update(TABLE.NOTE, values, selection, selectionArgs);
+                break;
+            case URI_NOTE_ITEM:
+                id = uri.getPathSegments().get(1);
+                increaseNoteVersion(Long.valueOf(id), selection, selectionArgs);
+                count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
+                        + parseSelection(selection), selectionArgs);
+                break;
+            case URI_DATA:
+                count = db.update(TABLE.DATA, values, selection, selectionArgs);
+                updateData = true;
+                break;
+            case URI_DATA_ITEM:
+                id = uri.getPathSegments().get(1);
+                count = db.update(TABLE.DATA, values, DataColumns.ID + "=" + id
+                        + parseSelection(selection), selectionArgs);
+                updateData = true;
+                break;
+            default:
+                throw new IllegalArgumentException("Unknown URI " + uri);
+        }
+
+        if (count > 0) {
+            if (updateData) {
+                getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null);
+            }
+            getContext().getContentResolver().notifyChange(uri, null);
+        }
+        return count;
+    }
+
     private String parseSelection(String selection) {
-        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");// SQL查询：模糊搜索笔记内容
-    }// SQL查询：模糊搜索笔记内容
-    // SQL查询：模糊搜索笔记内容
+        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
+    }
+
+    private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
+        StringBuilder sql = new StringBuilder(120);
+        sql.append("UPDATE ");
+        sql.append(TABLE.NOTE);
+        sql.append(" SET ");
+        sql.append(NoteColumns.VERSION);
+        sql.append("=" + NoteColumns.VERSION + "+1 ");
+
+        if (id > 0 || !TextUtils.isEmpty(selection)) {
+            sql.append(" WHERE ");
+        }
+        if (id > 0) {
+            sql.append(NoteColumns.ID + "=" + String.valueOf(id));
+        }
+        if (!TextUtils.isEmpty(selection)) {
+            String selectString = id > 0 ? parseSelection(selection) : selection;
+            for (String args : selectionArgs) {
+                selectString = selectString.replaceFirst("\\?", args);
+            }
+            sql.append(selectString);
+        }
+
+        mHelper.getWritableDatabase().execSQL(sql.toString());
+    }
+
     @Override
-    public String getType(Uri uri) {// SQL查询：模糊搜索笔记内容
-        return null; // 不使用MIME类型// SQL查询：模糊搜索笔记内容
-    }// SQL查询：模糊搜索笔记内容
-}// SQL查询：模糊搜索笔记内容
+    public String getType(Uri uri) {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+}
diff --git a/app/src/main/java/net/micode/notes/gtask/data/MetaData.java b/app/src/main/java/net/micode/notes/gtask/data/MetaData.java
index d9ec370..3a2050b 100644
--- a/app/src/main/java/net/micode/notes/gtask/data/MetaData.java
+++ b/app/src/main/java/net/micode/notes/gtask/data/MetaData.java
@@ -1,83 +1,82 @@
 /*
- * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)// 定义包名
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
  *
- * Licensed under the Apache License, Version 2.0 (the "License");// 定义包名
- * you may not use this file except in compliance with the License.// 定义包名
- * You may obtain a copy of the License at// 定义包名
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
- *        http://www.apache.org/licenses/LICENSE-2.0// 定义包名
+ *        http://www.apache.org/licenses/LICENSE-2.0
  *
- * Unless required by applicable law or agreed to in writing, software// 定义包名
- * distributed under the License is distributed on an "AS IS" BASIS,// 定义包名
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.// 定义包名
- * See the License for the specific language governing permissions and// 定义包名
- * limitations under the License.// 定义包名
- */// 定义包名
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 
-package net.micode.notes.gtask.data; // 定义包名
-// 定义包名
-import android.database.Cursor; // 导入Cursor类
-import android.util.Log; // 导入Log类
-// 定义包名
-import net.micode.notes.tool.GTaskStringUtils; // 导入GTaskStringUtils类
-// 定义包名
-import org.json.JSONException; // 导入JSONException类
-import org.json.JSONObject; // 导入JSONObject类
-// 定义包名
-public class MetaData extends Task { // 定义MetaData类，继承自Task类
-    private final static String TAG = MetaData.class.getSimpleName(); // 定义日志标签
-    // 定义包名
-    private String mRelatedGid = null; // 定义一个字符串变量用于存储相关的GID
-    // 定义包名
-    // 设置元数据的方法
-    public void setMeta(String gid, JSONObject metaInfo) {// 定义包名
-        try {// 定义包名
-            metaInfo.put(GTaskStringUtils.META_HEAD_GTASK_ID, gid); // 将GID放入metaInfo中// 定义包名
-        } catch (JSONException e) {// 定义包名
-            Log.e(TAG, "failed to put related gid"); // 捕获异常并记录错误日志// 定义包名
-        }// 定义包名
-        setNotes(metaInfo.toString()); // 将metaInfo转换为字符串并设置为笔记内容// 定义包名
-        setName(GTaskStringUtils.META_NOTE_NAME); // 设置笔记名称// 定义包名
-    }// 定义包名
-    // 定义包名
-    // 获取相关GID的方法
-    public String getRelatedGid() {// 定义包名
-        return mRelatedGid; // 返回相关GID// 定义包名
-    }// 定义包名
-    // 定义包名
-    @Override// 定义包名
-    public boolean isWorthSaving() {// 定义包名
-        return getNotes() != null; // 判断笔记内容是否不为空// 定义包名
-    }// 定义包名
-    // 定义包名
-    @Override// 定义包名
-    public void setContentByRemoteJSON(JSONObject js) {// 定义包名
-        super.setContentByRemoteJSON(js); // 调用父类方法设置内容// 定义包名
-        if (getNotes() != null) { // 如果笔记内容不为空// 定义包名
-            try {// 定义包名
-                JSONObject metaInfo = new JSONObject(getNotes().trim()); // 将笔记内容转换为JSONObject// 定义包名
-                mRelatedGid = metaInfo.getString(GTaskStringUtils.META_HEAD_GTASK_ID); // 获取相关GID// 定义包名
-            } catch (JSONException e) {// 定义包名
-                Log.w(TAG, "failed to get related gid"); // 捕获异常并记录警告日志// 定义包名
-                mRelatedGid = null; // 将相关GID设置为空// 定义包名
-            }// 定义包名
-        }// 定义包名
-    }// 定义包名
-    // 定义包名
-    @Override// 定义包名
-    public void setContentByLocalJSON(JSONObject js) {// 定义包名
-        // 这个方法不应该被调用
-        throw new IllegalAccessError("MetaData:setContentByLocalJSON should not be called");// 定义包名
-    }// 定义包名
-    // 定义包名
-    @Override// 定义包名
-    public JSONObject getLocalJSONFromContent() {// 定义包名
-        throw new IllegalAccessError("MetaData:getLocalJSONFromContent should not be called");// 定义包名
-    }// 定义包名
-    // 定义包名
-    @Override// 定义包名
-    public int getSyncAction(Cursor c) {// 定义包名
-        throw new IllegalAccessError("MetaData:getSyncAction should not be called");// 定义包名
-    }// 定义包名
-// 定义包名
-}// 定义包名
+package net.micode.notes.gtask.data;
+
+import android.database.Cursor;
+import android.util.Log;
+
+import net.micode.notes.tool.GTaskStringUtils;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+
+public class MetaData extends Task {
+    private final static String TAG = MetaData.class.getSimpleName();
+
+    private String mRelatedGid = null;
+
+    public void setMeta(String gid, JSONObject metaInfo) {
+        try {
+            metaInfo.put(GTaskStringUtils.META_HEAD_GTASK_ID, gid);
+        } catch (JSONException e) {
+            Log.e(TAG, "failed to put related gid");
+        }
+        setNotes(metaInfo.toString());
+        setName(GTaskStringUtils.META_NOTE_NAME);
+    }
+
+    public String getRelatedGid() {
+        return mRelatedGid;
+    }
+
+    @Override
+    public boolean isWorthSaving() {
+        return getNotes() != null;
+    }
+
+    @Override
+    public void setContentByRemoteJSON(JSONObject js) {
+        super.setContentByRemoteJSON(js);
+        if (getNotes() != null) {
+            try {
+                JSONObject metaInfo = new JSONObject(getNotes().trim());
+                mRelatedGid = metaInfo.getString(GTaskStringUtils.META_HEAD_GTASK_ID);
+            } catch (JSONException e) {
+                Log.w(TAG, "failed to get related gid");
+                mRelatedGid = null;
+            }
+        }
+    }
+
+    @Override
+    public void setContentByLocalJSON(JSONObject js) {
+        // this function should not be called
+        throw new IllegalAccessError("MetaData:setContentByLocalJSON should not be called");
+    }
+
+    @Override
+    public JSONObject getLocalJSONFromContent() {
+        throw new IllegalAccessError("MetaData:getLocalJSONFromContent should not be called");
+    }
+
+    @Override
+    public int getSyncAction(Cursor c) {
+        throw new IllegalAccessError("MetaData:getSyncAction should not be called");
+    }
+
+}
diff --git a/app/src/main/java/net/micode/notes/gtask/data/Node.java b/app/src/main/java/net/micode/notes/gtask/data/Node.java
index e5b5947..63950e0 100644
--- a/app/src/main/java/net/micode/notes/gtask/data/Node.java
+++ b/app/src/main/java/net/micode/notes/gtask/data/Node.java
@@ -1,101 +1,101 @@
 /*
- * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)//
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
  *
- * Licensed under the Apache License, Version 2.0 (the "License");//
- * you may not use this file except in compliance with the License.//
- * You may obtain a copy of the License at//
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
- *        http://www.apache.org/licenses/LICENSE-2.0//
+ *        http://www.apache.org/licenses/LICENSE-2.0
  *
- * Unless required by applicable law or agreed to in writing, software//
- * distributed under the License is distributed on an "AS IS" BASIS,//
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.//
- * See the License for the specific language governing permissions and//
- * limitations under the License.//
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
-package net.micode.notes.gtask.data; // 定义包名
+package net.micode.notes.gtask.data;
 
-import android.database.Cursor; // 导入Cursor类
+import android.database.Cursor;
 
-import org.json.JSONObject; // 导入JSONObject类
+import org.json.JSONObject;
 
-public abstract class Node { // 定义抽象类Node
-    public static final int SYNC_ACTION_NONE = 0; // 定义常量，表示无同步操作
+public abstract class Node {
+    public static final int SYNC_ACTION_NONE = 0;
 
-    public static final int SYNC_ACTION_ADD_REMOTE = 1; // 定义常量，表示添加到远程
+    public static final int SYNC_ACTION_ADD_REMOTE = 1;
 
-    public static final int SYNC_ACTION_ADD_LOCAL = 2; // 定义常量，表示添加到本地
+    public static final int SYNC_ACTION_ADD_LOCAL = 2;
 
-    public static final int SYNC_ACTION_DEL_REMOTE = 3; // 定义常量，表示从远程删除
+    public static final int SYNC_ACTION_DEL_REMOTE = 3;
 
-    public static final int SYNC_ACTION_DEL_LOCAL = 4; // 定义常量，表示从本地删除
+    public static final int SYNC_ACTION_DEL_LOCAL = 4;
 
-    public static final int SYNC_ACTION_UPDATE_REMOTE = 5; // 定义常量，表示更新到远程
+    public static final int SYNC_ACTION_UPDATE_REMOTE = 5;
 
-    public static final int SYNC_ACTION_UPDATE_LOCAL = 6; // 定义常量，表示更新到本地
+    public static final int SYNC_ACTION_UPDATE_LOCAL = 6;
 
-    public static final int SYNC_ACTION_UPDATE_CONFLICT = 7; // 定义常量，表示更新冲突
+    public static final int SYNC_ACTION_UPDATE_CONFLICT = 7;
 
-    public static final int SYNC_ACTION_ERROR = 8; // 定义常量，表示同步错误
+    public static final int SYNC_ACTION_ERROR = 8;
 
-    private String mGid; // 定义私有变量mGid，存储GID
+    private String mGid;
 
-    private String mName; // 定义私有变量mName，存储名称
+    private String mName;
 
-    private long mLastModified; // 定义私有变量mLastModified，存储最后修改时间
+    private long mLastModified;
 
-    private boolean mDeleted; // 定义私有变量mDeleted，存储删除状态
+    private boolean mDeleted;
 
-    public Node() { // 构造函数，初始化变量
-        mGid = null; // 初始化mGid为null
-        mName = ""; // 初始化mName为空字符串
-        mLastModified = 0; // 初始化mLastModified为0
-        mDeleted = false; // 初始化mDeleted为false
+    public Node() {
+        mGid = null;
+        mName = "";
+        mLastModified = 0;
+        mDeleted = false;
     }
 
-    public abstract JSONObject getCreateAction(int actionId); // 抽象方法，获取创建操作的JSON对象
+    public abstract JSONObject getCreateAction(int actionId);
 
-    public abstract JSONObject getUpdateAction(int actionId); // 抽象方法，获取更新操作的JSON对象
+    public abstract JSONObject getUpdateAction(int actionId);
 
-    public abstract void setContentByRemoteJSON(JSONObject js); // 抽象方法，通过远程JSON设置内容
+    public abstract void setContentByRemoteJSON(JSONObject js);
 
-    public abstract void setContentByLocalJSON(JSONObject js); // 抽象方法，通过本地JSON设置内容
+    public abstract void setContentByLocalJSON(JSONObject js);
 
-    public abstract JSONObject getLocalJSONFromContent(); // 抽象方法，从内容获取本地JSON对象
+    public abstract JSONObject getLocalJSONFromContent();
 
-    public abstract int getSyncAction(Cursor c); // 抽象方法，获取同步操作
+    public abstract int getSyncAction(Cursor c);
 
-    public void setGid(String gid) { // 设置GID的方法
+    public void setGid(String gid) {
         this.mGid = gid;
     }
 
-    public void setName(String name) { // 获取删除状态的方法
+    public void setName(String name) {
         this.mName = name;
-    }/ 获取删除状态的方法
-/ 获取删除状态的方法
-    public void setLastModified(long lastModified) { // 设置最后修改时间的方法
-        this.mLastModified = lastModified;/ 获取删除状态的方法
-    }/ 获取删除状态的方法
-/ 获取删除状态的方法
-    public void setDeleted(boolean deleted) { / 获取删除状态的方法
+    }
+
+    public void setLastModified(long lastModified) {
+        this.mLastModified = lastModified;
+    }
+
+    public void setDeleted(boolean deleted) {
         this.mDeleted = deleted;
-    }/ 获取删除状态的方法
-/ 获取删除状态的方法
-    public String getGid() { // 获取GID的方法
-        return this.mGid;/ 获取删除状态的方法
-    }/ 获取删除状态的方法
-/ 获取删除状态的方法
-    public String getName() { // 获取名称的方法
-        return this.mName;/ 获取删除状态的方法
-    }/ 获取删除状态的方法
-/ 获取删除状态的方法
-    public long getLastModified() { // 获取最后修改时间的方法
-        return this.mLastModified;/ 获取删除状态的方法
-    }/ 获取删除状态的方法/ 获取删除状态的方法
-/ 获取删除状态的方法
-    public boolean getDeleted() { // 获取删除状态的方法
-        return this.mDeleted;/ 获取删除状态的方法
-    }/ 获取删除状态的方法
-/ 获取删除状态的方法
-}/ 获取删除状态的方法
+    }
+
+    public String getGid() {
+        return this.mGid;
+    }
+
+    public String getName() {
+        return this.mName;
+    }
+
+    public long getLastModified() {
+        return this.mLastModified;
+    }
+
+    public boolean getDeleted() {
+        return this.mDeleted;
+    }
+
+}
diff --git a/app/src/main/java/net/micode/notes/gtask/data/SqlData.java b/app/src/main/java/net/micode/notes/gtask/data/SqlData.java
index 7f9dc6b..d3ec3be 100644
--- a/app/src/main/java/net/micode/notes/gtask/data/SqlData.java
+++ b/app/src/main/java/net/micode/notes/gtask/data/SqlData.java
@@ -1,186 +1,189 @@
 /*
- * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)//
+ * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
  *
- * Licensed under the Apache License, Version 2.0 (the "License");//
- * you may not use this file except in compliance with the License.//
- * You may obtain a copy of the License at//
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
  *
- *        http://www.apache.org/licenses/LICENSE-2.0//
+ *        http://www.apache.org/licenses/LICENSE-2.0
  *
- * Unless required by applicable law or agreed to in writing, software//
- * distributed under the License is distributed on an "AS IS" BASIS,//
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.//
- * See the License for the specific language governing permissions and//
- * limitations under the License.//
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
  */
 
-package net.micode.notes.gtask.data;//
-
-import android.content.ContentResolver;//
-import android.content.ContentUris;//
-import android.content.ContentValues;//
-import android.content.Context;//
-import android.database.Cursor;//
-import android.net.Uri;//
-import android.util.Log;//
-
-import net.micode.notes.data.Notes;//
-import net.micode.notes.data.Notes.DataColumns;//
-import net.micode.notes.data.Notes.DataConstants;//
-import net.micode.notes.data.Notes.NoteColumns;//
-import net.micode.notes.data.NotesDatabaseHelper.TABLE;//
-import net.micode.notes.gtask.exception.ActionFailureException;//
-//
-import org.json.JSONException;//
-import org.json.JSONObject;//
-//
+package net.micode.notes.gtask.data;
+
+import android.content.ContentResolver;
+import android.content.ContentUris;
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.Cursor;
+import android.net.Uri;
+import android.util.Log;
+
+import net.micode.notes.data.Notes;
+import net.micode.notes.data.Notes.DataColumns;
+import net.micode.notes.data.Notes.DataConstants;
+import net.micode.notes.data.Notes.NoteColumns;
+import net.micode.notes.data.NotesDatabaseHelper.TABLE;
+import net.micode.notes.gtask.exception.ActionFailureException;
+
+import org.json.JSONException;
+import org.json.JSONObject;
+
+
 public class SqlData {
-    private static final String TAG = SqlData.class.getSimpleName();  // 定义日志标签
-//
-    private static final int INVALID_ID = -99999;  // 无效ID常量
-//
-    // 定义查询数据库时所需要的字段
+    private static final String TAG = SqlData.class.getSimpleName();
+
+    private static final int INVALID_ID = -99999;
+
     public static final String[] PROJECTION_DATA = new String[] {
-            DataColumns.ID, DataColumns.MIME_TYPE, DataColumns.CONTENT, DataColumns.DATA1,//
-            DataColumns.DATA3//
-    };//
-//
-    // 数据库列的索引
-    public static final int DATA_ID_COLUMN = 0;//
-    public static final int DATA_MIME_TYPE_COLUMN = 1;//
-    public static final int DATA_CONTENT_COLUMN = 2;//
-    public static final int DATA_CONTENT_DATA_1_COLUMN = 3;//
-    public static final int DATA_CONTENT_DATA_3_COLUMN = 4;//
-//
-    private ContentResolver mContentResolver;  // 用于访问ContentProvider的ContentResolver
-    private boolean mIsCreate;  // 标记当前对象是否是新创建的
-    private long mDataId;  // 数据ID
-    private String mDataMimeType;  // 数据类型
-    private String mDataContent;  // 数据内容
-    private long mDataContentData1;  // 数据内容的附加信息1
-    private String mDataContentData3;  // 数据内容的附加信息3
-    private ContentValues mDiffDataValues;  // 用于存储更改的数据内容
-
-    // 构造函数，初始化SqlData对象
+            DataColumns.ID, DataColumns.MIME_TYPE, DataColumns.CONTENT, DataColumns.DATA1,
+            DataColumns.DATA3
+    };
+
+    public static final int DATA_ID_COLUMN = 0;
+
+    public static final int DATA_MIME_TYPE_COLUMN = 1;
+
+    public static final int DATA_CONTENT_COLUMN = 2;
+
+    public static final int DATA_CONTENT_DATA_1_COLUMN = 3;
+
+    public static final int DATA_CONTENT_DATA_3_COLUMN = 4;
+
+    private ContentResolver mContentResolver;
+
+    private boolean mIsCreate;
+
+    private long mDataId;
+
+    private String mDataMimeType;
+
+    private String mDataContent;
+
+    private long mDataContentData1;
+
+    private String mDataContentData3;
+
+    private ContentValues mDiffDataValues;
+
     public SqlData(Context context) {
-        mContentResolver = context.getContentResolver();  // 获取ContentResolver
-        mIsCreate = true;  // 标记为新创建
-        mDataId = INVALID_ID;  // 初始化为无效ID
-        mDataMimeType = DataConstants.NOTE;  // 默认数据类型为NOTE
-        mDataContent = "";  // 默认内容为空
-        mDataContentData1 = 0;  // 默认附加信息1为0
-        mDataContentData3 = "";  // 默认附加信息3为空
-        mDiffDataValues = new ContentValues();  // 初始化更改数据的ContentValues
-    }//
-//
-    // 构造函数，通过Cur/sor加载数据
+        mContentResolver = context.getContentResolver();
+        mIsCreate = true;
+        mDataId = INVALID_ID;
+        mDataMimeType = DataConstants.NOTE;
+        mDataContent = "";
+        mDataContentData1 = 0;
+        mDataContentData3 = "";
+        mDiffDataValues = new ContentValues();
+    }
+
     public SqlData(Context context, Cursor c) {
-        mContentResolver = context.getContentResolver();  // 获取ContentResolver
-        mIsCreate = false;  // 标记为已存在数据
-        loadFromCursor(c);  // 从Cursor中加载数据
-        mDiffDataValues = new ContentValues();  // 初始化更改数据的ContentValues
-    }//
-//
-    // 从Cursor加载数据
-    private void loadFromCursor(Cursor c) {//
-        mDataId = c.getLong(DATA_ID_COLUMN);  // 获取数据ID
-        mDataMimeType = c.getString(DATA_MIME_TYPE_COLUMN);  // 获取数据类型
-        mDataContent = c.getString(DATA_CONTENT_COLUMN);  // 获取数据内容
-        mDataContentData1 = c.getLong(DATA_CONTENT_DATA_1_COLUMN);  // 获取附加信息1
-        mDataContentData3 = c.getString(DATA_CONTENT_DATA_3_COLUMN);  // 获取附加信息3
-    }//
-//
-    // 设置数据内容
+        mContentResolver = context.getContentResolver();
+        mIsCreate = false;
+        loadFromCursor(c);
+        mDiffDataValues = new ContentValues();
+    }
+
+    private void loadFromCursor(Cursor c) {
+        mDataId = c.getLong(DATA_ID_COLUMN);
+        mDataMimeType = c.getString(DATA_MIME_TYPE_COLUMN);
+        mDataContent = c.getString(DATA_CONTENT_COLUMN);
+        mDataContentData1 = c.getLong(DATA_CONTENT_DATA_1_COLUMN);
+        mDataContentData3 = c.getString(DATA_CONTENT_DATA_3_COLUMN);
+    }
+
     public void setContent(JSONObject js) throws JSONException {
-        long dataId = js.has(DataColumns.ID) ? js.getLong(DataColumns.ID) : INVALID_ID;  // 获取ID，如果没有则设置为无效ID
-        if (mIsCreate || mDataId != dataId) {  // 如果是新创建的或者ID不相同
-            mDiffDataValues.put(DataColumns.ID, dataId);  // 将ID放入更改数据中
-        }//
-        mDataId = dataId;  // 更新数据ID
-//
-        String dataMimeType = js.has(DataColumns.MIME_TYPE) ? js.getString(DataColumns.MIME_TYPE)//
-                : DataConstants.NOTE;  // 获取数据类型，默认是NOTE
-        if (mIsCreate || !mDataMimeType.equals(dataMimeType)) {  // 如果是新创建的或者类型不相同
-            mDiffDataValues.put(DataColumns.MIME_TYPE, dataMimeType);  // 将数据类型放入更改数据中
-        }//
-        mDataMimeType = dataMimeType;  // 更新数据类型
-//
-        String dataContent = js.has(DataColumns.CONTENT) ? js.getString(DataColumns.CONTENT) : "";  // 获取内容
-        if (mIsCreate || !mDataContent.equals(dataContent)) {  // 如果是新创建的或者内容不相同
-            mDiffDataValues.put(DataColumns.CONTENT, dataContent);  // 将内容放入更改数据中
-        }//
-        mDataContent = dataContent;  // 更新内容 // 清空更改的数据
-        // 清空更改的数据
-        long dataContentData1 = js.has(DataColumns.DATA1) ? js.getLong(DataColumns.DATA1) : 0;  // 获取附加信息1
-        if (mIsCreate || mDataContentData1 != dataContentData1) {  // 如果是新创建的或者附加信息1不同
-            mDiffDataValues.put(DataColumns.DATA1, dataContentData1);  // 将附加信息1放入更改数据中
-        } // 清空更改的数据
-        mDataContentData1 = dataContentData1;  // 更新附加信息1
-        // 清空更改的数据
-        String dataContentData3 = js.has(DataColumns.DATA3) ? js.getString(DataColumns.DATA3) : "";  // 获取附加信息3
-        if (mIsCreate || !mDataContentData3.equals(dataContentData3)) {  // 如果是新创建的或者附加信息3不同
-            mDiffDataValues.put(DataColumns.DATA3, dataContentData3);  // 将附加信息3放入更改数据中
-        } // 清空更改的数据
-        mDataContentData3 = dataContentData3;  // 更新附加信息3
-    } // 清空更改的数据
-    // 清空更改的数据
-    // 获取数据内容
-    public JSONObject getContent() throws JSONException {//
-        if (mIsCreate) {  // 如果是新创建的
-            Log.e(TAG, "it seems that we haven't created this in database yet");  // 打印错误日志
-            return null;  // 返回null
-        }// 返回null
-        JSONObject js = new JSONObject();  // 创建一个新的JSONObject
-        js.put(DataColumns.ID, mDataId);  // 将ID放入JSONObject中
-        js.put(DataColumns.MIME_TYPE, mDataMimeType);  // 将数据类型放入JSONObject中
-        js.put(DataColumns.CONTENT, mDataContent);  // 将内容放入JSONObject中
-        js.put(DataColumns.DATA1, mDataContentData1);  // 将附加信息1放入JSONObject中
-        js.put(DataColumns.DATA3, mDataContentData3);  // 将附加信息3放入JSONObject中
-        return js;  // 返回JSONObject
-    } // 清空更改的数据
-    // 清空更改的数据
-    // 提交更改
-    public void commit(long noteId, boolean validateVersion, long version) {//
-        if (mIsCreate) {  // 如果是新创建的
-            if (mDataId == INVALID_ID && mDiffDataValues.containsKey(DataColumns.ID)) {  // 如果ID无效并且有ID更改
-                mDiffDataValues.remove(DataColumns.ID);  // 移除ID字段
-            } // 清空更改的数据
-            // 清空更改的数据
-            mDiffDataValues.put(DataColumns.NOTE_ID, noteId);  // 将笔记ID放入更改数据中
-            Uri uri = mContentResolver.insert(Notes.CONTENT_DATA_URI, mDiffDataValues);  // 插入数据到ContentProvider
-            try { // 清空更改的数据
-                mDataId = Long.valueOf(uri.getPathSegments().get(1));  // 获取插入数据的ID
-            } catch (NumberFormatException e) { // 清空更改的数据
-                Log.e(TAG, "Get note id error :" + e.toString());  // 打印日志
-                throw new ActionFailureException("create note failed");  // 抛出异常
-            } // 清空更改的数据
-        } else {  // 如果不是新创建的
-            if (mDiffDataValues.size() > 0) {  // 如果有更改的数据
-                int result = 0; // 清空更改的数据
-                if (!validateVersion) {  // 如果不需要版本验证 // 清空更改的数据
-                    result = mContentResolver.update(ContentUris.withAppendedId( // 清空更改的数据
-                            Notes.CONTENT_DATA_URI, mDataId), mDiffDataValues, null, null);  // 更新数据
-                } else {  // 如果需要版本验证
-                    result = mContentResolver.update(ContentUris.withAppendedId( // 清空更改的数据
-                                    Notes.CONTENT_DATA_URI, mDataId), mDiffDataValues, // 清空更改的数据
-                            " ? in (SELECT " + NoteColumns.ID + " FROM " + TABLE.NOTE // 清空更改的数据
-                                    + " WHERE " + NoteColumns.VERSION + "=?)", new String[] { // 清空更改的数据
-                                    String.valueOf(noteId), String.valueOf(version) // 清空更改的数据
-                            }); // 清空更改的数据
-                } // 清空更改的数据
-                if (result == 0) {  // 如果没有更新数据
-                    Log.w(TAG, "there is no update. maybe user updates note when syncing");  // 打印警告日志
-                } // 清空更改的数据
-            } // 清空更改的数据
-        } // 清空更改的数据
-        // 清空更改的数据
-        // 清空更改的数据
-        mDiffDataValues.clear();  // 清空更改的数据
-        mIsCreate = false;  // 标记为非新创建
-    } // 清空更改的数据
-    // 清空更改的数据
-    // 获取数据ID
-    public long getId() { // 清空更改的数据
-        return mDataId;  // 返回数据ID
-    } // 清空更改的数据
-} // 清空更改的数据
+        long dataId = js.has(DataColumns.ID) ? js.getLong(DataColumns.ID) : INVALID_ID;
+        if (mIsCreate || mDataId != dataId) {
+            mDiffDataValues.put(DataColumns.ID, dataId);
+        }
+        mDataId = dataId;
+
+        String dataMimeType = js.has(DataColumns.MIME_TYPE) ? js.getString(DataColumns.MIME_TYPE)
+                : DataConstants.NOTE;
+        if (mIsCreate || !mDataMimeType.equals(dataMimeType)) {
+            mDiffDataValues.put(DataColumns.MIME_TYPE, dataMimeType);
+        }
+        mDataMimeType = dataMimeType;
+
+        String dataContent = js.has(DataColumns.CONTENT) ? js.getString(DataColumns.CONTENT) : "";
+        if (mIsCreate || !mDataContent.equals(dataContent)) {
+            mDiffDataValues.put(DataColumns.CONTENT, dataContent);
+        }
+        mDataContent = dataContent;
+
+        long dataContentData1 = js.has(DataColumns.DATA1) ? js.getLong(DataColumns.DATA1) : 0;
+        if (mIsCreate || mDataContentData1 != dataContentData1) {
+            mDiffDataValues.put(DataColumns.DATA1, dataContentData1);
+        }
+        mDataContentData1 = dataContentData1;
+
+        String dataContentData3 = js.has(DataColumns.DATA3) ? js.getString(DataColumns.DATA3) : "";
+        if (mIsCreate || !mDataContentData3.equals(dataContentData3)) {
+            mDiffDataValues.put(DataColumns.DATA3, dataContentData3);
+        }
+        mDataContentData3 = dataContentData3;
+    }
+
+    public JSONObject getContent() throws JSONException {
+        if (mIsCreate) {
+            Log.e(TAG, "it seems that we haven't created this in database yet");
+            return null;
+        }
+        JSONObject js = new JSONObject();
+        js.put(DataColumns.ID, mDataId);
+        js.put(DataColumns.MIME_TYPE, mDataMimeType);
+        js.put(DataColumns.CONTENT, mDataContent);
+        js.put(DataColumns.DATA1, mDataContentData1);
+        js.put(DataColumns.DATA3, mDataContentData3);
+        return js;
+    }
+
+    public void commit(long noteId, boolean validateVersion, long version) {
+
+        if (mIsCreate) {
+            if (mDataId == INVALID_ID && mDiffDataValues.containsKey(DataColumns.ID)) {
+                mDiffDataValues.remove(DataColumns.ID);
+            }
+
+            mDiffDataValues.put(DataColumns.NOTE_ID, noteId);
+            Uri uri = mContentResolver.insert(Notes.CONTENT_DATA_URI, mDiffDataValues);
+            try {
+                mDataId = Long.valueOf(uri.getPathSegments().get(1));
+            } catch (NumberFormatException e) {
+                Log.e(TAG, "Get note id error :" + e.toString());
+                throw new ActionFailureException("create note failed");
+            }
+        } else {
+            if (mDiffDataValues.size() > 0) {
+                int result = 0;
+                if (!validateVersion) {
+                    result = mContentResolver.update(ContentUris.withAppendedId(
+                            Notes.CONTENT_DATA_URI, mDataId), mDiffDataValues, null, null);
+                } else {
+                    result = mContentResolver.update(ContentUris.withAppendedId(
+                            Notes.CONTENT_DATA_URI, mDataId), mDiffDataValues,
+                            " ? in (SELECT " + NoteColumns.ID + " FROM " + TABLE.NOTE
+                                    + " WHERE " + NoteColumns.VERSION + "=?)", new String[] {
+                                    String.valueOf(noteId), String.valueOf(version)
+                            });
+                }
+                if (result == 0) {
+                    Log.w(TAG, "there is no update. maybe user updates note when syncing");
+                }
+            }
+        }
+
+        mDiffDataValues.clear();
+        mIsCreate = false;
+    }
+
+    public long getId() {
+        return mDataId;
+    }
+}
diff --git a/app/src/main/java/net/micode/notes/gtask/data/SqlNote.java b/app/src/main/java/net/micode/notes/gtask/data/SqlNote.java
index ec76b2a..79a4095 100644
--- a/app/src/main/java/net/micode/notes/gtask/data/SqlNote.java
+++ b/app/src/main/java/net/micode/notes/gtask/data/SqlNote.java
@@ -200,13 +200,6 @@ public class SqlNote {
         mVersion = c.getLong(VERSION_COLUMN);
     }
 
-
-
-
-
-
-
-    
     private void loadDataContent() {
         Cursor c = null;
         mDataList.clear();
diff --git a/app/src/main/java/net/micode/notes/gtask/data/Task.java b/app/src/main/java/net/micode/notes/gtask/data/Task.java
index 828c4ed..6a19454 100644
--- a/app/src/main/java/net/micode/notes/gtask/data/Task.java
+++ b/app/src/main/java/net/micode/notes/gtask/data/Task.java
@@ -33,357 +33,319 @@ import org.json.JSONObject;
 
 
 public class Task extends Node {
-    private static final String TAG = Task.class.getSimpleName();  // Tag for logging
+    private static final String TAG = Task.class.getSimpleName();
 
-    private boolean mCompleted;  // Flag indicating task completion status
+    private boolean mCompleted;
 
-    private String mNotes;  // Stores notes related to the task
+    private String mNotes;
 
-    private JSONObject mMetaInfo;  // Metadata for task
+    private JSONObject mMetaInfo;
 
-    private Task mPriorSibling;  // Reference to the previous task in the same list
+    private Task mPriorSibling;
 
-    private TaskList mParent;  // Reference to the parent task list
+    private TaskList mParent;
 
-    // Constructor
     public Task() {
         super();
-        mCompleted = false;  // Initialize task as not completed
-        mNotes = null;  // Initialize notes as null
-        mPriorSibling = null;  // Initialize prior sibling as null
-        mParent = null;  // Initialize parent as null
-        mMetaInfo = null;  // Initialize metadata as null
+        mCompleted = false;
+        mNotes = null;
+        mPriorSibling = null;
+        mParent = null;
+        mMetaInfo = null;
     }
 
-    // Creates a JSON object representing a task creation action
     public JSONObject getCreateAction(int actionId) {
-        JSONObject js = new JSONObject();  // Create a new JSONObject to hold the action details
+        JSONObject js = new JSONObject();
 
         try {
-            // Set action type to "create"
+            // action_type
             js.put(GTaskStringUtils.GTASK_JSON_ACTION_TYPE,
                     GTaskStringUtils.GTASK_JSON_ACTION_TYPE_CREATE);
 
-            // Set the action ID
+            // action_id
             js.put(GTaskStringUtils.GTASK_JSON_ACTION_ID, actionId);
 
-            // Set the task index within its parent task list
+            // index
             js.put(GTaskStringUtils.GTASK_JSON_INDEX, mParent.getChildTaskIndex(this));
 
-            // Set the entity delta which holds the task details
+            // entity_delta
             JSONObject entity = new JSONObject();
-            entity.put(GTaskStringUtils.GTASK_JSON_NAME, getName());  // Set the task name
-            entity.put(GTaskStringUtils.GTASK_JSON_CREATOR_ID, "null");  // Set the creator as null (default)
+            entity.put(GTaskStringUtils.GTASK_JSON_NAME, getName());
+            entity.put(GTaskStringUtils.GTASK_JSON_CREATOR_ID, "null");
             entity.put(GTaskStringUtils.GTASK_JSON_ENTITY_TYPE,
-                    GTaskStringUtils.GTASK_JSON_TYPE_TASK);  // Set entity type to task
+                    GTaskStringUtils.GTASK_JSON_TYPE_TASK);
             if (getNotes() != null) {
-                entity.put(GTaskStringUtils.GTASK_JSON_NOTES, getNotes());  // Add notes if present
+                entity.put(GTaskStringUtils.GTASK_JSON_NOTES, getNotes());
             }
-            js.put(GTaskStringUtils.GTASK_JSON_ENTITY_DELTA, entity);  // Add entity to the action
+            js.put(GTaskStringUtils.GTASK_JSON_ENTITY_DELTA, entity);
 
-            // Set parent ID (the ID of the parent task list)
+            // parent_id
             js.put(GTaskStringUtils.GTASK_JSON_PARENT_ID, mParent.getGid());
 
-            // Set the destination parent type
+            // dest_parent_type
             js.put(GTaskStringUtils.GTASK_JSON_DEST_PARENT_TYPE,
                     GTaskStringUtils.GTASK_JSON_TYPE_GROUP);
 
-            // Set the list ID (the ID of the parent task list)
+            // list_id
             js.put(GTaskStringUtils.GTASK_JSON_LIST_ID, mParent.getGid());
 
-            // Set prior sibling ID if there's a prior sibling
+            // prior_sibling_id
             if (mPriorSibling != null) {
                 js.put(GTaskStringUtils.GTASK_JSON_PRIOR_SIBLING_ID, mPriorSibling.getGid());
             }
 
-        } catch (JSONException e) {  // Catch JSON exception if any occur
-            Log.e(TAG, e.toString());  // Log the error
-            e.printStackTrace();  // Print the stack trace
-            throw new ActionFailureException("fail to generate task-create jsonobject");  // Throw custom exception
+        } catch (JSONException e) {
+            Log.e(TAG, e.toString());
+            e.printStackTrace();
+            throw new ActionFailureException("fail to generate task-create jsonobject");
         }
 
-        return js;  // Return the JSON object representing the create action
+        return js;
     }
 
-    // Creates a JSON object representing a task update action
     public JSONObject getUpdateAction(int actionId) {
-        JSONObject js = new JSONObject();  // Create a new JSONObject for the update action
+        JSONObject js = new JSONObject();
 
         try {
-            // Set action type to "update"
+            // action_type
             js.put(GTaskStringUtils.GTASK_JSON_ACTION_TYPE,
                     GTaskStringUtils.GTASK_JSON_ACTION_TYPE_UPDATE);
 
-            // Set action ID
+            // action_id
             js.put(GTaskStringUtils.GTASK_JSON_ACTION_ID, actionId);
 
-            // Set task ID
+            // id
             js.put(GTaskStringUtils.GTASK_JSON_ID, getGid());
 
-            // Set the entity delta with task details
+            // entity_delta
             JSONObject entity = new JSONObject();
-            entity.put(GTaskStringUtils.GTASK_JSON_NAME, getName());  // Set the task name
+            entity.put(GTaskStringUtils.GTASK_JSON_NAME, getName());
             if (getNotes() != null) {
-                entity.put(GTaskStringUtils.GTASK_JSON_NOTES, getNotes());  // Add notes if available
+                entity.put(GTaskStringUtils.GTASK_JSON_NOTES, getNotes());
             }
-            entity.put(GTaskStringUtils.GTASK_JSON_DELETED, getDeleted());  // Set deletion status
-            js.put(GTaskStringUtils.GTASK_JSON_ENTITY_DELTA, entity);  // Add entity to the update action
+            entity.put(GTaskStringUtils.GTASK_JSON_DELETED, getDeleted());
+            js.put(GTaskStringUtils.GTASK_JSON_ENTITY_DELTA, entity);
 
-        } catch (JSONException e) {  // Catch JSON exception if any occur
-            Log.e(TAG, e.toString());  // Log the error
-            e.printStackTrace();  // Print the stack trace
-            throw new ActionFailureException("fail to generate task-update jsonobject");  // Throw custom exception
+        } catch (JSONException e) {
+            Log.e(TAG, e.toString());
+            e.printStackTrace();
+            throw new ActionFailureException("fail to generate task-update jsonobject");
         }
 
-        return js;  // Return the JSON object representing the update action
+        return js;
     }
 
-    // Sets the task content based on a remote JSON object
     public void setContentByRemoteJSON(JSONObject js) {
         if (js != null) {
             try {
-                // Set task ID if available
+                // id
                 if (js.has(GTaskStringUtils.GTASK_JSON_ID)) {
                     setGid(js.getString(GTaskStringUtils.GTASK_JSON_ID));
                 }
 
-                // Set last modified timestamp if available
+                // last_modified
                 if (js.has(GTaskStringUtils.GTASK_JSON_LAST_MODIFIED)) {
                     setLastModified(js.getLong(GTaskStringUtils.GTASK_JSON_LAST_MODIFIED));
                 }
 
-                // Set task name if available
+                // name
                 if (js.has(GTaskStringUtils.GTASK_JSON_NAME)) {
                     setName(js.getString(GTaskStringUtils.GTASK_JSON_NAME));
                 }
 
-                // Set notes if available
+                // notes
                 if (js.has(GTaskStringUtils.GTASK_JSON_NOTES)) {
                     setNotes(js.getString(GTaskStringUtils.GTASK_JSON_NOTES));
                 }
 
-                // Set deletion status if available
+                // deleted
                 if (js.has(GTaskStringUtils.GTASK_JSON_DELETED)) {
                     setDeleted(js.getBoolean(GTaskStringUtils.GTASK_JSON_DELETED));
                 }
 
-                // Set completion status if available
+                // completed
                 if (js.has(GTaskStringUtils.GTASK_JSON_COMPLETED)) {
                     setCompleted(js.getBoolean(GTaskStringUtils.GTASK_JSON_COMPLETED));
                 }
-            } catch (JSONException e) {  // Catch JSON exception if any occur
-                Log.e(TAG, e.toString());  // Log the error
-                e.printStackTrace();  // Print the stack trace
-                throw new ActionFailureException("fail to get task content from jsonobject");  // Throw custom exception
+            } catch (JSONException e) {
+                Log.e(TAG, e.toString());
+                e.printStackTrace();
+                throw new ActionFailureException("fail to get task content from jsonobject");
             }
         }
     }
 
-    // Sets the task content based on a local JSON object
     public void setContentByLocalJSON(JSONObject js) {
         if (js == null || !js.has(GTaskStringUtils.META_HEAD_NOTE)
                 || !js.has(GTaskStringUtils.META_HEAD_DATA)) {
-            Log.w(TAG, "setContentByLocalJSON: nothing is available");  // Log a warning if data is not available
+            Log.w(TAG, "setContentByLocalJSON: nothing is avaiable");
         }
 
         try {
-            JSONObject note = js.getJSONObject(GTaskStringUtils.META_HEAD_NOTE);  // Get the note object
-            JSONArray dataArray = js.getJSONArray(GTaskStringUtils.META_HEAD_DATA);  // Get data array
+            JSONObject note = js.getJSONObject(GTaskStringUtils.META_HEAD_NOTE);
+            JSONArray dataArray = js.getJSONArray(GTaskStringUtils.META_HEAD_DATA);
 
-            // Check if the note type is valid
             if (note.getInt(NoteColumns.TYPE) != Notes.TYPE_NOTE) {
-                Log.e(TAG, "invalid type");  // Log an error if the type is invalid
-                return;  // Exit the method
+                Log.e(TAG, "invalid type");
+                return;
             }
 
-            // Iterate through data array and set the task name
             for (int i = 0; i < dataArray.length(); i++) {
                 JSONObject data = dataArray.getJSONObject(i);
                 if (TextUtils.equals(data.getString(DataColumns.MIME_TYPE), DataConstants.NOTE)) {
-                    setName(data.getString(DataColumns.CONTENT));  // Set the task name
+                    setName(data.getString(DataColumns.CONTENT));
                     break;
                 }
             }
 
-        } catch (JSONException e) {  // Catch JSON exception if any occur
-            Log.e(TAG, e.toString());  // Log the error
-            e.printStackTrace();  // Print the stack trace
+        } catch (JSONException e) {
+            Log.e(TAG, e.toString());
+            e.printStackTrace();
         }
     }
 
-    // Returns a local JSON representation of the task content
     public JSONObject getLocalJSONFromContent() {
-        String name = getName();  // Get the task name
+        String name = getName();
         try {
-            if (mMetaInfo == null) {  // If metadata is null, create a new task
-                // New task created from the web
-                if (name == null) {  // If the task name is null, log a warning
+            if (mMetaInfo == null) {
+                // new task created from web
+                if (name == null) {
                     Log.w(TAG, "the note seems to be an empty one");
-                    return null;  // Return null if the task name is empty
+                    return null;
                 }
 
-                // Create a new JSON object for the task
                 JSONObject js = new JSONObject();
                 JSONObject note = new JSONObject();
                 JSONArray dataArray = new JSONArray();
                 JSONObject data = new JSONObject();
-                data.put(DataColumns.CONTENT, name);  // Set the task name in the data
-                dataArray.put(data);  // Add data to the array
-                js.put(GTaskStringUtils.META_HEAD_DATA, dataArray);  // Add data array to the JSON object
-                note.put(NoteColumns.TYPE, Notes.TYPE_NOTE);  // Set note type to "note"
-                js.put(GTaskStringUtils.META_HEAD_NOTE, note);  // Add note object to the JSON object
-                return js;  // Return the newly created JSON object
+                data.put(DataColumns.CONTENT, name);
+                dataArray.put(data);
+                js.put(GTaskStringUtils.META_HEAD_DATA, dataArray);
+                note.put(NoteColumns.TYPE, Notes.TYPE_NOTE);
+                js.put(GTaskStringUtils.META_HEAD_NOTE, note);
+                return js;
             } else {
-                // Synced task, retrieve data from metadata
-                JSONObject note = mMetaInfo.getJSONObject(GTaskStringUtils.META_HEAD_NOTE);  // Get the note object
-                JSONArray dataArray = mMetaInfo.getJSONArray(GTaskStringUtils.META_HEAD_DATA);  // Get data array
-
-                // Iterate through data array and update task name
-                for (int i = 0; i < dataArray.length(); i++) {// Return null if an error occurs
-                    JSONObject data = dataArray.getJSONObject(i);// Return null if an error occurs
-                    if (TextUtils.equals(data.getString(DataColumns.MIME_TYPE), DataConstants.NOTE)) {// Return null if an error occurs
-                        data.put(DataColumns.CONTENT, getName());  // Set the task name in data
-                        break;// Return null if an error occurs
-                    }// Return null if an error occurs
-                }// Return null if an error occurs
-// Return null if an error occurs
-                note.put(NoteColumns.TYPE, Notes.TYPE_NOTE);  // Set note type to "note"
-                return mMetaInfo;  // Return the metadata as the JSON object
+                // synced task
+                JSONObject note = mMetaInfo.getJSONObject(GTaskStringUtils.META_HEAD_NOTE);
+                JSONArray dataArray = mMetaInfo.getJSONArray(GTaskStringUtils.META_HEAD_DATA);
+
+                for (int i = 0; i < dataArray.length(); i++) {
+                    JSONObject data = dataArray.getJSONObject(i);
+                    if (TextUtils.equals(data.getString(DataColumns.MIME_TYPE), DataConstants.NOTE)) {
+                        data.put(DataColumns.CONTENT, getName());
+                        break;
+                    }
+                }
+
+                note.put(NoteColumns.TYPE, Notes.TYPE_NOTE);
+                return mMetaInfo;
             }
-        } catch (JSONException e) {  // Catch JSON exception if any occur
-            Log.e(TAG, e.toString());  // Log the error
-            e.printStackTrace();  // Print the stack trace
-            return null;  // Return null if an error occurs
-        }// Return null if an error occurs
-    }// Return null if an error occurs
-}// Return null if an error occurs
-
-// Return null if an error occurs
-// Return null if an error occurs
-// Return null if an error occurs
-// Return null if an error occurs
-// Return null if an error occurs
-// Return null if an error occurs
-// Method to set meta information using a MetaData object
-public void setMetaInfo(MetaData metaData) {
-    // Check if the metaData is not null and contains notes
-    if (metaData != null && metaData.getNotes() != null) {
-        try {
-            // Convert the notes data into a JSONObject and assign it to mMetaInfo
-            mMetaInfo = new JSONObject(metaData.getNotes());
         } catch (JSONException e) {
-            // Log a warning if the conversion fails
-            Log.w(TAG, e.toString());
-            // Reset mMetaInfo to null in case of an error
-            mMetaInfo = null; // Reset mMetaInfo to null in case of an error
-        } // Reset mMetaInfo to null in case of an error
-    } // Reset mMetaInfo to null in case of an error
-} // Reset mMetaInfo to null in case of an error
-// Reset mMetaInfo to null in case of an error
-// Method to determine the sync action based on the data in the cursor
-public int getSyncAction(Cursor c) { // Reset mMetaInfo to null in case of an error
-    try { // Reset mMetaInfo to null in case of an error
-        JSONObject noteInfo = null; // Reset mMetaInfo to null in case of an error
-        // Reset mMetaInfo to null in case of an error
-        // Check if mMetaInfo is not null and contains the note info
-        if (mMetaInfo != null && mMetaInfo.has(GTaskStringUtils.META_HEAD_NOTE)) { // Reset mMetaInfo to null in case of an error
-            // Retrieve the note info from mMetaInfo
-            noteInfo = mMetaInfo.getJSONObject(GTaskStringUtils.META_HEAD_NOTE); // Reset mMetaInfo to null in case of an error
-        } // Reset mMetaInfo to null in case of an error
-        // Reset mMetaInfo to null in case of an error
-        // If no note info is found, return SYNC_ACTION_UPDATE_REMOTE
-        if (noteInfo == null) { // Reset mMetaInfo to null in case of an error
-            Log.w(TAG, "it seems that note meta has been deleted"); // Reset mMetaInfo to null in case of an error
-            return SYNC_ACTION_UPDATE_REMOTE; // Reset mMetaInfo to null in case of an error
-        } // Reset mMetaInfo to null in case of an error
-        // Reset mMetaInfo to null in case of an error
-        // If no note ID is found in the note info, return SYNC_ACTION_UPDATE_LOCAL
-        if (!noteInfo.has(NoteColumns.ID)) {
-            Log.w(TAG, "remote note id seems to be deleted");
-            return SYNC_ACTION_UPDATE_LOCAL;
-        } // Reset mMetaInfo to null in case of an error
-        // Reset mMetaInfo to null in case of an error
-        // Validate the note ID with the value in the cursor
-        if (c.getLong(SqlNote.ID_COLUMN) != noteInfo.getLong(NoteColumns.ID)) { // Reset mMetaInfo to null in case of an error
-            Log.w(TAG, "note id doesn't match"); // Reset mMetaInfo to null in case of an error
-            return SYNC_ACTION_UPDATE_LOCAL; // Reset mMetaInfo to null in case of an error
-            // Reset mMetaInfo to null in case of an error
-        // Check if there are any local updates
-        if (c.getInt(SqlNote.LOCAL_MODIFIED_COLUMN) == 0) {
-            // If no local updates, check if the sync ID matches the last modified timestamp
-            if (c.getLong(SqlNote.SYNC_ID_COLUMN) == getLastModified()) {
-                // No updates on either side // Reset mMetaInfo to null in case of an error
-                return SYNC_ACTION_NONE; // Reset mMetaInfo to null in case of an error
-            } else { // Reset mMetaInfo to null in case of an error
-                // Apply remote updates to local // Reset mMetaInfo to null in case of an error
-                return SYNC_ACTION_UPDATE_LOCAL; // Reset mMetaInfo to null in case of an error
-            } // Reset mMetaInfo to null in case of an error
-        } else { // Reset mMetaInfo to null in case of an error
-            // If there are local modifications,  // Reset mMetaInfo to null in case of an errorvalidate the gtask ID
-            if (!c.getString(SqlNote.GTASK_ID_COLUMN).equals(getGid())) { // Reset mMetaInfo to null in case of an error
-                Log.e(TAG, "gtask id doesn't match"); // Reset mMetaInfo to null in case of an error
-                return SYNC_ACTION_ERROR; // Reset mMetaInfo to null in case of an error
-            } // Reset mMetaInfo to null in case of an error
-            // Check if the sync ID matches the last modified timestamp for local modification
-            if (c.getLong(SqlNote.SYNC_ID_COLUMN) == getLastModified()) { // Reset mMetaInfo to null in case of an error
-                // Local modification only
-                return SYNC_ACTION_UPDATE_REMOTE; // Reset mMetaInfo to null in case of an error
-                // Conflict between local and remote modification
-                return SYNC_ACTION_UPDATE_CONFLICT; // Reset mMetaInfo to null in case of an error
-            } // Reset mMetaInfo to null in case of an error
-        } // Reset mMetaInfo to null in case of an error
-    } catch (Exception e) { // Reset mMetaInfo to null in case of an error
-        // Log the exception and return SYNC_ACTION_ERROR
-        Log.e(TAG, e.toString()); // Reset mMetaInfo to null in case of an error
-        e.printStackTrace(); // Reset mMetaInfo to null in case of an error
-    } // Reset mMetaInfo to null in case of an error
-        // Reset mMetaInfo to null in case of an error
-    return SYNC_ACTION_ERROR; // Reset mMetaInfo to null in case of an error
-} // Reset mMetaInfo to null in case of an error
-// Getter method to retrieve the parent task list
-// Method to check if the task is worth saving based on meta info or task content
-public boolean isWorthSaving() { // Reset mMetaInfo to null in case of an error
-    // If there is meta info or non-empty name or notes, return true
-    return mMetaInfo != null || (getName() != null && getName().trim().length() > 0)// Getter method to retrieve the parent task list
-            || (getNotes() != null && getNotes().trim().length() > 0);// Getter method to retrieve the parent task list
-} // Reset mMetaInfo to null in case of an error
-    // Reset mMetaInfo to null in case of an error
-// Setter method to mark the task as completed
-public void setCompleted(boolean completed) { // Reset mMetaInfo to null in case of an error
-    this.mCompleted = completed;// Getter method to retrieve the parent task list
-}// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-// Setter method to set the notes of the task
-public void setNotes(String notes) {// Getter method to retrieve the parent task list
-    this.mNotes = notes;// Getter method to retrieve the parent task list
-}// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-// Setter method to set the prior sibling task
-public void setPriorSibling(Task priorSibling) {// Getter method to retrieve the parent task list
-    this.mPriorSibling = priorSibling;// Getter method to retrieve the parent task list
-}// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-// Setter method to set the parent task list
-public void setParent(TaskList parent) {// Getter method to retrieve the parent task list
-    this.mParent = parent;// Getter method to retrieve the parent task list
-}// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-// Getter method to retrieve the completed status of the task
-public boolean getCompleted() {// Getter method to retrieve the parent task list
-    return this.mCompleted;// Getter method to retrieve the parent task list
-}// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-// Getter method to retrieve the notes of the task
-public String getNotes() {// Getter method to retrieve the parent task list
-    return this.mNotes;// Getter method to retrieve the parent task list
-}// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-// Getter method to retrieve the prior sibling task
-public Task getPriorSibling() {// Getter method to retrieve the parent task list
-    return this.mPriorSibling;// Getter method to retrieve the parent task list
-}// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-// Getter method to retrieve the parent task list
-public TaskList getParent() {// Getter method to retrieve the parent task list
-    return this.mParent;// Getter method to retrieve the parent task list
+            Log.e(TAG, e.toString());
+            e.printStackTrace();
+            return null;
+        }
+    }
+
+    public void setMetaInfo(MetaData metaData) {
+        if (metaData != null && metaData.getNotes() != null) {
+            try {
+                mMetaInfo = new JSONObject(metaData.getNotes());
+            } catch (JSONException e) {
+                Log.w(TAG, e.toString());
+                mMetaInfo = null;
+            }
+        }
+    }
+
+    public int getSyncAction(Cursor c) {
+        try {
+            JSONObject noteInfo = null;
+            if (mMetaInfo != null && mMetaInfo.has(GTaskStringUtils.META_HEAD_NOTE)) {
+                noteInfo = mMetaInfo.getJSONObject(GTaskStringUtils.META_HEAD_NOTE);
+            }
+
+            if (noteInfo == null) {
+                Log.w(TAG, "it seems that note meta has been deleted");
+                return SYNC_ACTION_UPDATE_REMOTE;
+            }
+
+            if (!noteInfo.has(NoteColumns.ID)) {
+                Log.w(TAG, "remote note id seems to be deleted");
+                return SYNC_ACTION_UPDATE_LOCAL;
+            }
+
+            // validate the note id now
+            if (c.getLong(SqlNote.ID_COLUMN) != noteInfo.getLong(NoteColumns.ID)) {
+                Log.w(TAG, "note id doesn't match");
+                return SYNC_ACTION_UPDATE_LOCAL;
+            }
+
+            if (c.getInt(SqlNote.LOCAL_MODIFIED_COLUMN) == 0) {
+                // there is no local update
+                if (c.getLong(SqlNote.SYNC_ID_COLUMN) == getLastModified()) {
+                    // no update both side
+                    return SYNC_ACTION_NONE;
+                } else {
+                    // apply remote to local
+                    return SYNC_ACTION_UPDATE_LOCAL;
+                }
+            } else {
+                // validate gtask id
+                if (!c.getString(SqlNote.GTASK_ID_COLUMN).equals(getGid())) {
+                    Log.e(TAG, "gtask id doesn't match");
+                    return SYNC_ACTION_ERROR;
+                }
+                if (c.getLong(SqlNote.SYNC_ID_COLUMN) == getLastModified()) {
+                    // local modification only
+                    return SYNC_ACTION_UPDATE_REMOTE;
+                } else {
+                    return SYNC_ACTION_UPDATE_CONFLICT;
+                }
+            }
+        } catch (Exception e) {
+            Log.e(TAG, e.toString());
+            e.printStackTrace();
+        }
+
+        return SYNC_ACTION_ERROR;
+    }
+
+    public boolean isWorthSaving() {
+        return mMetaInfo != null || (getName() != null && getName().trim().length() > 0)
+                || (getNotes() != null && getNotes().trim().length() > 0);
+    }
+
+    public void setCompleted(boolean completed) {
+        this.mCompleted = completed;
+    }
+
+    public void setNotes(String notes) {
+        this.mNotes = notes;
+    }
+
+    public void setPriorSibling(Task priorSibling) {
+        this.mPriorSibling = priorSibling;
+    }
+
+    public void setParent(TaskList parent) {
+        this.mParent = parent;
+    }
+
+    public boolean getCompleted() {
+        return this.mCompleted;
+    }
+
+    public String getNotes() {
+        return this.mNotes;
+    }
+
+    public Task getPriorSibling() {
+        return this.mPriorSibling;
+    }
+
+    public TaskList getParent() {
+        return this.mParent;
+    }
+
 }
diff --git a/build.gradle b/build.gradle
index f6627fc..ff6e6be 100644
--- a/build.gradle
+++ b/build.gradle
@@ -2,14 +2,19 @@
 buildscript {
     repositories {
         jcenter()
+        google()
+        mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.2'
+        //classpath 'com.android.tools.build:gradle:2.3.2'
+        classpath 'com.android.tools.build:gradle:7.4.2'
     }
 }
 
 allprojects {
     repositories {
         jcenter()
+        google()
+        mavenCentral()
     }
 }
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 6a932ea..4a3be83 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.11-rc-1-bin.zip