diff --git a/src/data/Contact.java b/src/data/Contact.java
new file mode 100644
index 0000000..cbc5b54
--- /dev/null
+++ b/src/data/Contact.java
@@ -0,0 +1,98 @@
+/*
+ * 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;
+import android.telephony.PhoneNumberUtils;
+import android.util.Log;
+
+import java.util.HashMap;
+
+/**
+ * 用于处理联系人信息的工具类，提供根据电话号码查询联系人姓名的功能。
+ */
+public class Contact {
+    // 用于缓存电话号码与联系人姓名的映射，减少频繁的数据库查询
+    private static HashMap<String, String> sContactCache;
+    
+    // 用于日志打印
+    private static final String TAG = "Contact";
+
+    // 用于查询联系人信息的 SQL 选择条件 (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 = '+')";
+
+    /**
+     * 根据电话号码查询联系人姓名，如果之前已经查询过该号码，会直接从缓存中获取
+     *
+     * @param context 上下文对象，用于访问联系人数据
+     * @param phoneNumber 需要查询的电话号码
+     * @return 对应电话号码的联系人姓名，如果没有找到，则返回 null
+     */
+    public static String getContact(Context context, String phoneNumber) {
+        // 如果缓存为空，初始化缓存 HashMap
+        if(sContactCache == null) {
+            sContactCache = new HashMap<String, String>();
+        }
+
+        // 如果缓存中已经有该电话号码的联系人信息，则直接返回缓存中的结果
+        if(sContactCache.containsKey(phoneNumber)) {
+            return sContactCache.get(phoneNumber);
+        }
+
+        // 替换 selection 中的占位符 "+" 为通过 PhoneNumberUtils 转换的号码格式
+        String selection = CALLER_ID_SELECTION.replace("+",
+                PhoneNumberUtils.toCallerIDMinMatch(phoneNumber));
+        
+        // 使用内容解析器查询联系人数据
+        Cursor cursor = context.getContentResolver().query(
+                Data.CONTENT_URI,  // 查询的 URI
+                new String[] { Phone.DISPLAY_NAME },  // 查询的列，获取联系人的显示名称
+                selection,  // 查询条件
+                new String[] { phoneNumber },  // 查询参数，传入电话号码
+                null);  // 不需要排序
+
+        // 如果查询成功且结果不为空
+        if (cursor != null && cursor.moveToFirst()) {
+            try {
+                // 获取联系人名称
+                String name = cursor.getString(0);
+                // 将联系人姓名存入缓存中，避免下次查询时再次访问数据库
+                sContactCache.put(phoneNumber, name);
+                return name;
+            } catch (IndexOutOfBoundsException e) {
+                // 如果在游标操作中出现异常，记录日志并返回 null
+                Log.e(TAG, " Cursor get string error " + e.toString());
+                return null;
+            } finally {
+                // 无论查询是否成功，都需要关闭游标
+                cursor.close();
+            }
+        } else {
+            // 如果没有找到匹配的联系人，记录日志并返回 null
+            Log.d(TAG, "No contact matched with number:" + phoneNumber);
+            return null;
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/data/Notes.java b/src/data/Notes.java
new file mode 100644
index 0000000..798c6bc
--- /dev/null
+++ b/src/data/Notes.java
@@ -0,0 +1,278 @@
+// 包声明，表明该类属于 net.micode.notes.data 包
+package net.micode.notes.data;
+
+// 导入所需的 Android 类，用于处理 URI 相关操作
+import android.net.Uri;
+
+// Notes 类的定义
+public class Notes {
+    // 定义一个字符串常量，用于表示权限
+    public static final String AUTHORITY = "micode_notes";
+    // 定义一个日志标签
+    public static final String TAG = "Notes";
+    // 定义三种类型的常量，分别表示笔记、文件夹和系统
+    public static final int TYPE_NOTE = 0;
+    public static final int TYPE_FOLDER = 1;
+    public static final int TYPE_SYSTEM = 2;
+
+    /**
+     * 以下是系统文件夹的标识符
+     * {@link Notes#ID_ROOT_FOLDER } 是默认文件夹
+     * {@link Notes#ID_TEMPARAY_FOLDER } 用于存储不属于任何文件夹的笔记
+     * {@link Notes#ID_CALL_RECORD_FOLDER} 用于存储通话记录
+     */
+    // 根文件夹的 ID
+    public static final int ID_ROOT_FOLDER = 0;
+    // 临时文件夹的 ID
+    public static final int ID_TEMPARAY_FOLDER = -1;
+    // 通话记录文件夹的 ID
+    public static final int ID_CALL_RECORD_FOLDER = -2;
+    // 垃圾桶文件夹的 ID
+    public static final int ID_TRASH_FOLER = -3;
+
+    // 定义一些 Intent 额外信息的字符串常量，可能用于在不同组件之间传递数据
+    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";
+
+    // 定义一些与小部件相关的类型常量
+    public static final int TYPE_WIDGET_INVALIDE = -1;
+    public static final int TYPE_WIDGET_2X = 0;
+    public static final int TYPE_WIDGET_4X = 1;
+
+    // DataConstants 内部类，可能用于存储一些数据相关的常量
+    public static class DataConstants {
+        // 定义文本笔记和通话笔记的内容项类型
+        public static final String NOTE = TextNote.CONTENT_ITEM_TYPE;
+        public static final String CALL_NOTE = CallNote.CONTENT_ITEM_TYPE;
+    }
+
+    /**
+     * 用于查询所有笔记和文件夹的 URI
+     */
+    // 通过拼接权限和路径生成的 URI
+    public static final Uri CONTENT_NOTE_URI = Uri.parse("content://" + AUTHORITY + "/note");
+
+    /**
+     * 用于查询数据的 URI
+     */
+    // 通过拼接权限和路径生成的 URI
+    public static final Uri CONTENT_DATA_URI = Uri.parse("content://" + AUTHORITY + "/data");
+
+    // 定义一个接口，包含了笔记列的信息
+    public interface NoteColumns {
+        /**
+         * 行的唯一 ID
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String ID = "_id";
+
+        /**
+         * 笔记或文件夹的父 ID
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String PARENT_ID = "parent_id";
+
+        /**
+         * 笔记或文件夹的创建日期
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String CREATED_DATE = "created_date";
+
+        /**
+         * 最新修改日期
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String MODIFIED_DATE = "modified_date";
+
+
+        /**
+         * 提醒日期
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String ALERTED_DATE = "alert_date";
+
+        /**
+         * 文件夹的名称或笔记的文本内容
+         * <P> 类型：TEXT </P>
+         */
+        public static final String SNIPPET = "snippet";
+
+        /**
+         * 笔记的小部件 ID
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String WIDGET_ID = "widget_id";
+
+        /**
+         * 笔记的小部件类型
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String WIDGET_TYPE = "widget_type";
+
+        /**
+         * 笔记的背景颜色 ID
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String BG_COLOR_ID = "bg_color_id";
+
+        /**
+         * 对于文本笔记，它没有附件；对于多媒体笔记，它至少有一个附件
+         * <P> 类型：INTEGER </P>
+         */
+        public static final String HAS_ATTACHMENT = "has_attachment";
+
+        /**
+         * 文件夹中的笔记数量
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String NOTES_COUNT = "notes_count";
+
+        /**
+         * 文件类型：文件夹或笔记
+         * <P> 类型：INTEGER </P>
+         */
+        public static final String TYPE = "type";
+
+        /**
+         * 最后同步的 ID
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String SYNC_ID = "sync_id";
+
+        /**
+         * 表示是否本地修改的标志
+         * <P> 类型：INTEGER </P>
+         */
+        public static final String LOCAL_MODIFIED = "local_modified";
+
+        /**
+         * 移动到临时文件夹之前的原始父 ID
+         * <P> 类型：INTEGER </P>
+         */
+        public static final String ORIGIN_PARENT_ID = "origin_parent_id";
+
+        /**
+         * gtask 的 ID
+         * <P> 类型：TEXT </P>
+         */
+        public static final String GTASK_ID = "gtask_id";
+
+        /**
+         * 版本代码
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String VERSION = "version";
+    }
+
+    // 定义一个接口，包含了数据列的信息
+    public interface DataColumns {
+        /**
+         * 行的唯一 ID
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String ID = "_id";
+
+        /**
+         * 该行表示的项的 MIME 类型
+         * <P> 类型：Text </P>
+         */
+        public static final String MIME_TYPE = "mime_type";
+
+        /**
+         * 该数据所属笔记的引用 ID
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String NOTE_ID = "note_id";
+
+        /**
+         * 笔记或文件夹的创建日期
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String CREATED_DATE = "created_date";
+
+        /**
+         * 最新修改日期
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String MODIFIED_DATE = "modified_date";
+
+        /**
+         * 数据的内容
+         * <P> 类型：TEXT </P>
+         */
+        public static final String CONTENT = "content";
+
+
+        /**
+         * 通用数据列，其含义取决于 {@link #MIMETYPE}，用于整数数据类型
+         * <P> 类型：INTEGER </P>
+         */
+        public static final String DATA1 = "data1";
+
+        /**
+         * 通用数据列，其含义取决于 {@link #MIMETYPE}，用于整数数据类型
+         * <P> 类型：INTEGER </P>
+         */
+        public static final String DATA2 = "data2";
+
+        /**
+         * 通用数据列，其含义取决于 {@link #MIMETYPE}，用于文本数据类型
+         * <P> 类型：TEXT </P>
+         */
+        public static final String DATA3 = "data3";
+
+        /**
+         * 通用数据列，其含义取决于 {@link #MIMETYPE}，用于文本数据类型
+         * <P> 类型：TEXT </P>
+         */
+        public static final String DATA4 = "data4";
+
+        /**
+         * 通用数据列，其含义取决于 {@link #MIMETYPE}，用于文本数据类型
+         * <P> 类型：TEXT </P>
+         */
+        public static final String DATA5 = "data5";
+    }
+
+    // 定义一个静态内部类 TextNote，实现了 DataColumns 接口，可能是为了表示文本笔记的数据信息
+    public static final class TextNote implements DataColumns {
+        /**
+         * 模式，指示文本是否处于复选列表模式
+         * <P> 类型：Integer 1: 复选列表模式 0: 正常模式 </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");
+    }
+
+    // 定义一个静态内部类 CallNote，实现了 DataColumns 接口，可能是为了表示通话笔记的数据信息
+    public static final class CallNote implements DataColumns {
+        /**
+         * 此记录的通话日期
+         * <P> 类型：INTEGER (long) </P>
+         */
+        public static final String CALL_DATE = DATA1;
+
+        /**
+         * 此记录的电话号码
+         * <P> 类型：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");
+    }
+}
\ No newline at end of file
diff --git a/src/data/NotesDatabaseHelper.java b/src/data/NotesDatabaseHelper.java
new file mode 100644
index 0000000..2474c66
--- /dev/null
+++ b/src/data/NotesDatabaseHelper.java
@@ -0,0 +1,337 @@
+// 该类继承自 SQLiteOpenHelper，用于管理笔记应用的数据库操作
+public class NotesDatabaseHelper extends SQLiteOpenHelper {
+    // 数据库名称
+    private static final String DB_NAME = "note.db";
+    // 数据库版本
+    private static final int DB_VERSION = 4;
+
+    // 定义表名的接口
+    public interface TABLE {
+        public static final String NOTE = "note";
+        public static final String DATA = "data";
+    }
+
+    // 日志标签
+    private static final String TAG = "NotesDatabaseHelper";
+    // 单例模式的实例
+    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 + "(" +
+            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" +
+        ")";
+
+    // 创建数据（笔记内容）表的 SQL 语句
+    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 ''" +
+        ")";
+
+    // 创建数据表的笔记 ID 索引的 SQL 语句
+    private static final String CREATE_DATA_NOTE_ID_INDEX_SQL =
+        "CREATE INDEX IF NOT EXISTS note_id_index ON " +
+        TABLE.DATA + "(" + DataColumns.NOTE_ID + ");";
+
+    // 当笔记的父 ID 更新时，增加父文件夹笔记数量的触发器 SQL 语句
+    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";
+
+    // 当笔记的父 ID 更新时，减少父文件夹笔记数量的触发器 SQL 语句
+    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";
+
+    // 当插入新笔记到文件夹时，增加父文件夹笔记数量的触发器 SQL 语句
+    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";
+
+    // 当从文件夹删除笔记时，减少父文件夹笔记数量的触发器 SQL 语句
+    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";
+
+    // 当插入数据类型为笔记时，更新笔记内容的触发器 SQL 语句
+    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";
+
+    // 当数据类型为笔记的数据更新时，更新笔记内容的触发器 SQL 语句
+    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";
+
+    // 当数据类型为笔记的数据删除时，更新笔记内容的触发器 SQL 语句
+    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";
+
+    // 当笔记删除时，删除属于该笔记的数据的触发器 SQL 语句
+    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";
+
+    // 当文件夹删除时，删除属于该文件夹的笔记的触发器 SQL 语句
+    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";
+
+    // 当文件夹移动到回收站时，移动属于该文件夹的笔记的触发器 SQL 语句
+    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";
+
+
+    // 构造函数，调用父类的构造函数
+    public NotesDatabaseHelper(Context context) {
+        super(context, DB_NAME, null, DB_VERSION);
+    }
+
+
+    // 创建笔记表的方法，执行 SQL 语句，重建触发器，创建系统文件夹
+    public void createNoteTable(SQLiteDatabase db) {
+        db.execSQL(CREATE_NOTE_TABLE_SQL);
+        reCreateNoteTableTriggers(db);
+        createSystemFolder(db);
+        Log.d(TAG, "note table has been created");
+    }
+
+
+    // 重建笔记表触发器的方法，先删除旧触发器，再创建新触发器
+    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);
+    }
+
+
+    // 创建系统文件夹的方法，向笔记表插入不同系统文件夹的记录
+    private void createSystemFolder(SQLiteDatabase db) {
+        ContentValues values = new ContentValues();
+
+        // 通话记录文件夹
+        values.put(NoteColumns.ID, Notes.ID_CALL_RECORD_FOLDER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
+
+        // 根文件夹
+        values.clear();
+        values.put(NoteColumns.ID, Notes.ID_ROOT_FOLDER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
+
+        // 临时文件夹
+        values.clear();
+        values.put(NoteColumns.ID, Notes.ID_TEMPARAY_FOLDER);
+        values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
+        db.insert(TABLE.NOTE, null, values);
+
+        // 回收站文件夹
+        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（笔记内容）表的方法，执行 SQL 语句，重建触发器，创建索引
+    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");
+    }
+
+
+    // 重建数据（笔记内容）表触发器的方法，先删除旧触发器，再创建新触发器
+    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);
+    }
+
+
+    // 获取单例的方法，确保只有一个实例存在
+    static synchronized NotesDatabaseHelper getInstance(Context context) {
+        if (mInstance == null) {
+            mInstance = new NotesDatabaseHelper(context);
+        }
+        return mInstance;
+    }
+
+
+    // 重写 onCreate 方法，创建数据库时调用创建笔记表和数据（笔记内容）表的方法
+    @Override
+    public void onCreate(SQLiteDatabase db) {
+        createNoteTable(db);
+        createDataTable(db);
+    }
+
+
+    // 重写 onUpgrade 方法，处理数据库升级
+    @Override
+    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
+        boolean reCreateTriggers = false;
+        boolean skipV2 = false;
+
+        if (oldVersion == 1) {
+            upgradeToV2(db);
+            skipV2 = true; // 这次升级包括从 v2 到 v3 的升级
+            oldVersion++;
+        }
+
+        if (oldVersion == 2 &&!skipV2) {
+            upgradeToV3(db);
+            reCreateTriggers = true;
+            oldVersion++;
+        }
+
+        if (oldVersion == 3) {
+            upgradeToV4(db);
+            oldVersion++;
+        }
+
+
+        if (reCreateTriggers) {
+            reCreateNoteTableTriggers(db);
+            reCreateDataTableTriggers(db);
+        }
+
+
+        if (oldVersion!= newVersion) {
+            throw new IllegalStateException("Upgrade notes database to version " + newVersion
+                    + "fails");
+        }
+    }
+
+
+    // 升级到 v2 的方法，删除旧表，重新创建笔记表和数据（笔记内容）表
+    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);
+    }
+
+
+    // 升级到 v3 的方法，删除旧触发器，添加新列，插入回收站系统文件夹
+    private void upgradeToV3(SQLiteDatabase db) {
+        // 删除未使用的触发器
+        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");
+        // 添加 gtask id 列
+        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
+                + " TEXT NOT NULL DEFAULT ''");
+        // 插入回收站系统文件夹
+        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);
+    }
+
+
+    // 升级到 v4 的方法，添加版本列
+    private void upgradeToV4(SQLiteDatabase db) {
+        db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
+                + " INTEGER NOT NULL DEFAULT 0");
+    }
+}
\ No newline at end of file
diff --git a/src/data/NotesProvider.java b/src/data/NotesProvider.java
new file mode 100644
index 0000000..1f092e9
--- /dev/null
+++ b/src/data/NotesProvider.java
@@ -0,0 +1,306 @@
+// 该类继承自 ContentProvider，用于为笔记应用提供内容提供器服务
+public class NotesProvider extends ContentProvider {
+    // 用于匹配不同 URI 的 UriMatcher
+    private static final UriMatcher mMatcher;
+    // 数据库辅助类的实例
+    private NotesDatabaseHelper mHelper;
+    // 日志标签
+    private static final String TAG = "NotesProvider";
+    // 定义不同 URI 的匹配码
+    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 {
+        // 初始化 UriMatcher，并添加不同的 URI 匹配规则
+        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);
+    }
+
+
+    // 搜索结果的投影，用于查询时显示的列信息
+    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;
+
+
+    // 搜索笔记片段的 SQL 查询语句
+    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;
+
+
+    // 当 ContentProvider 被创建时调用，获取数据库辅助类的单例
+    @Override
+    public boolean onCreate() {
+        mHelper = NotesDatabaseHelper.getInstance(getContext());
+        return true;
+    }
+
+
+    // 执行查询操作，根据不同的 URI 进行不同的查询处理
+    @Override
+    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)) {
+            // 查询笔记表
+            case URI_NOTE:
+                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
+                        sortOrder);
+                break;
+            // 查询笔记表的具体项
+            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;
+            // 查询数据表
+            case URI_DATA:
+                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
+                        sortOrder);
+                break;
+            // 查询数据表的具体项
+            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;
+            // 处理搜索和搜索建议的查询
+            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;
+    }
+
+
+    // 执行插入操作，根据不同的 URI 插入数据到不同的表中
+    @Override
+    public Uri insert(Uri uri, ContentValues values) {
+        SQLiteDatabase db = mHelper.getWritableDatabase();
+        long dataId = 0, noteId = 0, insertedId = 0;
+        switch (mMatcher.match(uri)) {
+            // 插入笔记表
+            case URI_NOTE:
+                insertedId = noteId = db.insert(TABLE.NOTE, null, values);
+                break;
+            // 插入数据表
+            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);
+        }
+        // 通知笔记 URI 的变化
+        if (noteId > 0) {
+            getContext().getContentResolver().notifyChange(
+                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
+        }
+
+
+        // 通知数据 URI 的变化
+        if (dataId > 0) {
+            getContext().getContentResolver().notifyChange(
+                    ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
+        }
+
+
+        return ContentUris.withAppendedId(uri, insertedId);
+    }
+
+
+    // 执行删除操作，根据不同的 URI 删除不同表中的数据
+    @Override
+    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)) {
+            // 删除笔记表中的数据
+            case URI_NOTE:
+                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 ";
+                count = db.delete(TABLE.NOTE, selection, selectionArgs);
+                break;
+            // 删除笔记表中的具体项
+            case URI_NOTE_ITEM:
+                id = uri.getPathSegments().get(1);
+                // 不允许删除系统文件夹（ID 小于等于 0）
+                long noteId = Long.valueOf(id);
+                if (noteId <= 0) {
+                    break;
+                }
+                count = db.delete(TABLE.NOTE,
+                        NoteColumns.ID + "=" + id + parseSelection(selection), selectionArgs);
+                break;
+            // 删除数据表中的数据
+            case URI_DATA:
+                count = db.delete(TABLE.DATA, selection, selectionArgs);
+                deleteData = true;
+                break;
+            // 删除数据表中的具体项
+            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;
+    }
+
+
+    // 执行更新操作，根据不同的 URI 更新不同表中的数据
+    @Override
+    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)) {
+            // 更新笔记表中的数据
+            case URI_NOTE:
+                increaseNoteVersion(-1, selection, selectionArgs);
+                count = db.update(TABLE.NOTE, values, selection, selectionArgs);
+                break;
+            // 更新笔记表中的具体项
+            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;
+            // 更新数据表中的数据
+            case URI_DATA:
+                count = db.update(TABLE.DATA, values, selection, selectionArgs);
+                updateData = true;
+                break;
+            // 更新数据表中的具体项
+            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;
+    }
+
+
+    // 解析选择条件，添加 AND 操作符
+    private String parseSelection(String selection) {
+        return (!TextUtils.isEmpty(selection)? " AND (" + selection + ')' : "");
+    }
+
+
+    // 增加笔记的版本号
+    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());
+    }
+
+
+    // 获取 URI 的类型，当前未实现
+    @Override
+    public String getType(Uri uri) {
+        // TODO Auto-generated method stub
+        return null;
+    }
+}
\ No newline at end of file