diff --git a/src/main/java/net/micode/notes/data/Contact.java b/src/main/java/net/micode/notes/data/Contact.java
index d97ac5d..199bb2a 100644
--- a/src/main/java/net/micode/notes/data/Contact.java
+++ b/src/main/java/net/micode/notes/data/Contact.java
@@ -1,22 +1,7 @@
-/*
- * 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.
- */
-
 package net.micode.notes.data;
 
 import android.content.Context;
+
 import android.database.Cursor;
 import android.provider.ContactsContract.CommonDataKinds.Phone;
 import android.provider.ContactsContract.Data;
@@ -24,29 +9,35 @@ import android.telephony.PhoneNumberUtils;
 import android.util.Log;
 
 import java.util.HashMap;
-
-public class Contact {
+//change
+public class Contact { //联系人
     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 "
+    // 定义字符串CALLER_ID_SELECTION
+    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 = '+')";
 
+    // 获取联系人
     public static String getContact(Context context, String phoneNumber) {
         if(sContactCache == null) {
             sContactCache = new HashMap<String, String>();
         }
 
+        // 查找HashMap中是否已有phoneNumber信息
         if(sContactCache.containsKey(phoneNumber)) {
             return sContactCache.get(phoneNumber);
         }
 
         String selection = CALLER_ID_SELECTION.replace("+",
                 PhoneNumberUtils.toCallerIDMinMatch(phoneNumber));
+        // 查找数据库中phoneNumber的信息
         Cursor cursor = context.getContentResolver().query(
                 Data.CONTENT_URI,
                 new String [] { Phone.DISPLAY_NAME },
@@ -54,20 +45,25 @@ public class Contact {
                 new String[] { phoneNumber },
                 null);
 
+        // 判定查询结果 
+        // moveToFirst()返回第一条
         if (cursor != null && cursor.moveToFirst()) {
             try {
+                // 找到相关信息
                 String name = cursor.getString(0);
                 sContactCache.put(phoneNumber, name);
                 return name;
+                // 异常
             } catch (IndexOutOfBoundsException e) {
                 Log.e(TAG, " Cursor get string error " + e.toString());
                 return null;
             } finally {
                 cursor.close();
             }
+            // 未找到相关信息
         } else {
             Log.d(TAG, "No contact matched with number:" + phoneNumber);
             return null;
         }
     }
-}
+}
\ No newline at end of file
diff --git a/src/main/java/net/micode/notes/data/Notes.java b/src/main/java/net/micode/notes/data/Notes.java
index f240604..7cf0140 100644
--- a/src/main/java/net/micode/notes/data/Notes.java
+++ b/src/main/java/net/micode/notes/data/Notes.java
@@ -1,25 +1,13 @@
-/*
- * 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.
- */
-
 package net.micode.notes.data;
 
+import android.content.ContentUris;
 import android.net.Uri;
+// Notes 类中定义了很多常量，这些常量大多是int型和string型
 public class Notes {
     public static final String AUTHORITY = "micode_notes";
     public static final String TAG = "Notes";
+
+    //以下三个常量对NoteColumns.TYPE的值进行设置时会用到
     public static final int TYPE_NOTE     = 0;
     public static final int TYPE_FOLDER   = 1;
     public static final int TYPE_SYSTEM   = 2;
@@ -35,12 +23,24 @@ public class Notes {
     public static final int ID_CALL_RECORD_FOLDER = -2;
     public static final int ID_TRASH_FOLER = -3;
 
-    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";
-    public static final String INTENT_EXTRA_WIDGET_TYPE = "net.micode.notes.widget_type";
-    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";
+    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";
+    public static final String INTENT_EXTRA_WIDGET_TYPE =
+
+            "net.micode.notes.widget_type";
+    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";
 
     public static final int TYPE_WIDGET_INVALIDE      = -1;
     public static final int TYPE_WIDGET_2X            = 0;
@@ -54,13 +54,20 @@ public class Notes {
     /**
      * Uri to query all notes and folders
      */
-    public static final Uri CONTENT_NOTE_URI = Uri.parse("content://" + AUTHORITY + "/note");
+    public static final Uri CONTENT_NOTE_URI = Uri.parse("content://" +
+
+            AUTHORITY + "/note");//定义查询便签和文件夹的指针。
+
+//    public static final Uri my_URI = ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI , 10);
 
     /**
      * Uri to query data
      */
-    public static final Uri CONTENT_DATA_URI = Uri.parse("content://" + AUTHORITY + "/data");
+    public static final Uri CONTENT_DATA_URI = Uri.parse("content://" +
+
+            AUTHORITY + "/data");//定义查找数据的指针。
 
+    // 定义NoteColumns的常量,用于后面创建数据库的表头
     public interface NoteColumns {
         /**
          * The unique ID for a row
@@ -72,7 +79,7 @@ public class Notes {
          * The parent's id for note or folder
          * <P> Type: INTEGER (long) </P>
          */
-        public static final String PARENT_ID = "parent_id";
+        public static final String PARENT_ID = "parent_id";//为什么会有parent_id
 
         /**
          * Created data for note or folder
@@ -140,7 +147,7 @@ public class Notes {
          * The last sync id
          * <P> Type: INTEGER (long) </P>
          */
-        public static final String SYNC_ID = "sync_id";
+        public static final String SYNC_ID = "sync_id";//同步
 
         /**
          * Sign to indicate local modified or not
@@ -165,8 +172,9 @@ public class Notes {
          * <P> Type : INTEGER (long) </P>
          */
         public static final String VERSION = "version";
-    }
+    }//这些常量主要是定义便签的属性的。
 
+    // 定义DataColumns的常量,用于后面创建数据库的表头
     public interface DataColumns {
         /**
          * The unique ID for a row
@@ -206,41 +214,45 @@ public class Notes {
 
 
         /**
-         * Generic data column, the meaning is {@link #MIMETYPE} specific, used for
+         * 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
+         * 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
+         * 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
+         * 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
+         * Generic data column, the meaning is {@link #MIMETYPE} specific, 
+         used for
          * TEXT data type
          * <P> Type: TEXT </P>
          */
         public static final String DATA5 = "data5";
-    }
-
+    }//主要是定义存储便签内容数据的
     public static final class TextNote implements DataColumns {
         /**
          * Mode to indicate the text in check list mode or not
@@ -250,12 +262,18 @@ public class Notes {
 
         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_TYPE =
 
-        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/text_note";
+                "vnd.android.cursor.dir/text_note";
 
-        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/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");
+    }//文本内容的数据结构
 
     public static final class CallNote implements DataColumns {
         /**
@@ -270,10 +288,16 @@ public class Notes {
          */
         public static final String PHONE_NUMBER = DATA3;
 
-        public static final String CONTENT_TYPE = "vnd.android.cursor.dir/call_note";
+        public static final String CONTENT_TYPE =
 
-        public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/call_note";
+                "vnd.android.cursor.dir/call_note";
 
-        public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/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");
+    }//电话内容的数据结构
+}
\ No newline at end of file
diff --git a/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java b/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java
index ffe5d57..aa5a860 100644
--- a/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java
+++ b/src/main/java/net/micode/notes/data/NotesDatabaseHelper.java
@@ -1,38 +1,22 @@
-/*
- * 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.
- */
-
 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.content.ContentValues;//就是用于保存一些数据（string boolean byte double float int long short ...）信息，这些信息可以被数据库操作时使用。
+import android.content.Context;//加载和访问资源。（android中主要是这两个功能，但是这里具体不清楚）
+import android.database.sqlite.SQLiteDatabase;//主要提供了对应于添加、删除、更新、查询的操作方法： insert()、delete()、update()和query()。配合content.values
+import android.database.sqlite.SQLiteOpenHelper;//用来管理数据的创建和版本更新
 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;
-
+//数据库操作，用SQLOpenhelper,对一些note和文件进行数据库的操作，比如删除文件后，将文件里的note也相应删除
 
 public class NotesDatabaseHelper extends SQLiteOpenHelper {
     private static final String DB_NAME = "note.db";
 
     private static final int DB_VERSION = 4;
 
-    public interface TABLE {
+    public interface TABLE {    //接口，分成note和data，在后面的程序里分别使用过
         public static final String NOTE = "note";
 
         public static final String DATA = "data";
@@ -43,179 +27,179 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
     private static NotesDatabaseHelper mInstance;
 
     private static final String CREATE_NOTE_TABLE_SQL =
-        "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" +
-        ")";
+            "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" +
+                    ")";//数据库中需要存储的项目的名称，就相当于创建一个表格的表头的内容。
 
     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 ''" +
-        ")";
+            "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 ''" +
+                    ")";//和上面的功能一样，主要是存储的项目不同
 
     private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
-        "CREATE INDEX IF NOT EXISTS note_id_index ON " +
-        TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";
+            "CREATE INDEX IF NOT EXISTS note_id_index ON " +
+                    TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";//存储便签编号的一个数据表格
 
     /**
      * 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";
+            "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";//在文件夹中移入一个Note之后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//在文件夹中移出一个Note之后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//在文件夹中插入一个Note之后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//在文件夹中删除一个Note之后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//在文件夹中对一个Note导入新的数据之后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//Note数据被修改后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//Note数据被删除后需要更改的数据的表格。
 
     /**
      * 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";
+            "CREATE TRIGGER delete_data_on_delete " +
+                    " AFTER DELETE ON " + TABLE.NOTE +
+                    " BEGIN" +
+                    "  DELETE FROM " + TABLE.DATA +
+                    "   WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" +
+                    " END";//删除已删除的便签的数据后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//删除已删除的文件夹的便签后需要更改的数据的表格。
 
     /**
      * 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";
+            "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";//还原垃圾桶中便签后需要更改的数据的表格。
 
     public NotesDatabaseHelper(Context context) {
         super(context, DB_NAME, null, DB_VERSION);
-    }
+    }//构造函数，传入数据库的名称和版本
 
     public void createNoteTable(SQLiteDatabase db) {
         db.execSQL(CREATE_NOTE_TABLE_SQL);
         reCreateNoteTableTriggers(db);
         createSystemFolder(db);
         Log.d(TAG, "note table has been created");
-    }
+    }//创建表格（用来存储标签属性）
 
     private void reCreateNoteTableTriggers(SQLiteDatabase db) {
         db.execSQL("DROP TRIGGER IF EXISTS increase_folder_count_on_update");
@@ -233,7 +217,8 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         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);
-    }
+    }//execSQL是数据库操作的API，主要是更改行为的SQL语句。
+    //在这里主要是用来重新创建上述定义的表格用的，先删除原来有的数据库的触发器再重新创建新的数据库
 
     private void createSystemFolder(SQLiteDatabase db) {
         ContentValues values = new ContentValues();
@@ -268,14 +253,14 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
-    }
+    }//创建几个系统文件夹
 
     public void createDataTable(SQLiteDatabase db) {
         db.execSQL(CREATE_DATA_TABLE_SQL);
         reCreateDataTableTriggers(db);
         db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
         Log.d(TAG, "data table has been created");
-    }
+    }//创建表格（用来存储标签内容）
 
     private void reCreateDataTableTriggers(SQLiteDatabase db) {
         db.execSQL("DROP TRIGGER IF EXISTS update_note_content_on_insert");
@@ -285,20 +270,22 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         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);
-    }
+    }//同上面的execSQL
 
     static synchronized NotesDatabaseHelper getInstance(Context context) {
         if (mInstance == null) {
             mInstance = new NotesDatabaseHelper(context);
         }
         return mInstance;
-    }
+    }//上网查是为解决同一时刻只能有一个线程执行.
+    //在写程序库代码时，有时有一个类需要被所有的其它类使用，
+    //但又要求这个类只能被实例化一次，是个服务类，定义一次，其它类使用同一个这个类的实例
 
     @Override
     public void onCreate(SQLiteDatabase db) {
         createNoteTable(db);
         createDataTable(db);
-    }
+    }//实现两个表格（上面创建的两个表格）
 
     @Override
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
@@ -331,14 +318,14 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
             throw new IllegalStateException("Upgrade notes database to version " + newVersion
                     + "fails");
         }
-    }
+    }//数据库版本的更新（数据库内容的更改）
 
     private void upgradeToV2(SQLiteDatabase db) {
         db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
         db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
         createNoteTable(db);
         createDataTable(db);
-    }
+    }//更新到V2版本
 
     private void upgradeToV3(SQLiteDatabase db) {
         // drop unused triggers
@@ -353,10 +340,10 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
-    }
+    }//更新到V3版本
 
     private void upgradeToV4(SQLiteDatabase db) {
         db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                 + " INTEGER NOT NULL DEFAULT 0");
-    }
-}
+    }//更新到V4版本,但是不知道V2、V3、V4是什么意思
+}
\ No newline at end of file
diff --git a/src/main/java/net/micode/notes/data/NotesProvider.java b/src/main/java/net/micode/notes/data/NotesProvider.java
index edb0a60..6897999 100644
--- a/src/main/java/net/micode/notes/data/NotesProvider.java
+++ b/src/main/java/net/micode/notes/data/NotesProvider.java
@@ -1,22 +1,5 @@
-/*
- * 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.
- */
-
 package net.micode.notes.data;
 
-
 import android.app.SearchManager;
 import android.content.ContentProvider;
 import android.content.ContentUris;
@@ -33,9 +16,15 @@ 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;
-
-
+//为存储和获取数据提供接口。可以在不同的应用程序之间共享数据
+//ContentProvider提供的方法
+//query：查询
+//insert：插入
+//update：更新
+//delete：删除
+//getType：得到数据类型
 public class NotesProvider extends ContentProvider {
+    // UriMatcher用于匹配Uri
     private static final UriMatcher mMatcher;
 
     private NotesDatabaseHelper mHelper;
@@ -51,7 +40,9 @@ public class NotesProvider extends ContentProvider {
     private static final int URI_SEARCH_SUGGEST  = 6;
 
     static {
+        // 创建UriMatcher时，调用UriMatcher(UriMatcher.NO_MATCH)表示不匹配任何路径的返回码
         mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
+        // 把需要匹配Uri路径全部给注册上
         mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE);
         mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM);
         mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA);
@@ -65,33 +56,40 @@ public class NotesProvider extends ContentProvider {
      * 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.
      */
+    // 声明 NOTES_SEARCH_PROJECTION
     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 + ","
-        + "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;
-
+            + 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;
+    // 声明NOTES_SNIPPET_SEARCH_QUERY
     private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION
-        + " FROM " + TABLE.NOTE
-        + " WHERE " + NoteColumns.SNIPPET + " LIKE ?"
-        + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
-        + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;
+            + " FROM " + TABLE.NOTE
+            + " WHERE " + NoteColumns.SNIPPET + " LIKE ?"
+            + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
+            + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;
 
     @Override
+    // Context只有在onCreate()中才被初始化
+    // 对mHelper进行实例化
     public boolean onCreate() {
         mHelper = NotesDatabaseHelper.getInstance(getContext());
         return true;
     }
 
     @Override
+    // 查询uri在数据库中对应的位置
     public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
-            String sortOrder) {
+                        String sortOrder) {
         Cursor c = null;
+        // 获取可读数据库
         SQLiteDatabase db = mHelper.getReadableDatabase();
         String id = null;
+        // 匹配查找uri
         switch (mMatcher.match(uri)) {
+            // 对于不同的匹配值，在数据库中查找相应的条目
             case URI_NOTE:
                 c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
                         sortOrder);
@@ -113,6 +111,7 @@ public class NotesProvider extends ContentProvider {
             case URI_SEARCH:
             case URI_SEARCH_SUGGEST:
                 if (sortOrder != null || projection != null) {
+                    // 不合法的参数异常
                     throw new IllegalArgumentException(
                             "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
                 }
@@ -120,6 +119,8 @@ public class NotesProvider extends ContentProvider {
                 String searchString = null;
                 if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
                     if (uri.getPathSegments().size() > 1) {
+                        // getPathSegments()方法得到一个String的List，
+                        // 在uri.getPathSegments().get(1)为第2个元素
                         searchString = uri.getPathSegments().get(1);
                     }
                 } else {
@@ -139,6 +140,7 @@ public class NotesProvider extends ContentProvider {
                 }
                 break;
             default:
+                // 抛出异常
                 throw new IllegalArgumentException("Unknown URI " + uri);
         }
         if (c != null) {
@@ -148,13 +150,17 @@ public class NotesProvider extends ContentProvider {
     }
 
     @Override
+    // 插入一个uri
     public Uri insert(Uri uri, ContentValues values) {
+        // 获得可写的数据库
         SQLiteDatabase db = mHelper.getWritableDatabase();
         long dataId = 0, noteId = 0, insertedId = 0;
         switch (mMatcher.match(uri)) {
+            // 新增一个条目
             case URI_NOTE:
                 insertedId = noteId = db.insert(TABLE.NOTE, null, values);
                 break;
+            // 如果存在，查找NOTE_ID
             case URI_DATA:
                 if (values.containsKey(DataColumns.NOTE_ID)) {
                     noteId = values.getAsLong(DataColumns.NOTE_ID);
@@ -167,6 +173,7 @@ public class NotesProvider extends ContentProvider {
                 throw new IllegalArgumentException("Unknown URI " + uri);
         }
         // Notify the note uri
+        // notifyChange获得一个ContextResolver对象并且更新里面的内容
         if (noteId > 0) {
             getContext().getContentResolver().notifyChange(
                     ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
@@ -178,13 +185,17 @@ public class NotesProvider extends ContentProvider {
                     ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
         }
 
+        // 返回插入的uri的路径
         return ContentUris.withAppendedId(uri, insertedId);
     }
 
     @Override
+    // 删除一个uri
     public int delete(Uri uri, String selection, String[] selectionArgs) {
+        //Uri代表要操作的数据，Android上可用的每种资源 -包括 图像、视频片段、音频资源等都可以用Uri来表示。
         int count = 0;
         String id = null;
+        // 获得可写的数据库
         SQLiteDatabase db = mHelper.getWritableDatabase();
         boolean deleteData = false;
         switch (mMatcher.match(uri)) {
@@ -228,6 +239,7 @@ public class NotesProvider extends ContentProvider {
     }
 
     @Override
+    // 更新一个uri
     public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
         int count = 0;
         String id = null;
@@ -267,10 +279,12 @@ public class NotesProvider extends ContentProvider {
         return count;
     }
 
+    // 将字符串解析成规定格式
     private String parseSelection(String selection) {
         return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
     }
 
+    //增加一个noteVersion
     private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
         StringBuilder sql = new StringBuilder(120);
         sql.append("UPDATE ");
@@ -293,6 +307,7 @@ public class NotesProvider extends ContentProvider {
             sql.append(selectString);
         }
 
+        // execSQL()方法可以执行insert、delete、update和CREATE TABLE之类有更改行为的SQL语句
         mHelper.getWritableDatabase().execSQL(sql.toString());
     }
 
@@ -302,4 +317,4 @@ public class NotesProvider extends ContentProvider {
         return null;
     }
 
-}
+}
\ No newline at end of file