diff --git a/NotesDatabaseHelper.java.txt b/NotesDatabaseHelper.java.txt
deleted file mode 100644
index 25b1619..0000000
--- a/NotesDatabaseHelper.java.txt
+++ /dev/null
@@ -1,350 +0,0 @@
-NotesDatabaseHelper.java
-package net.micode.notes.data;
- 
-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 {    //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";
-    }
- 
-    private static final String TAG = "NotesDatabaseHelper";
- 
-    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" +
-        ")";//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 ''" +
-        ")";//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 + ");";//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";//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";//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";//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";//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";//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";//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";//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";//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";//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";//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");
-        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);
-    }//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();
- 
-        /**
-         * 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");
-        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);
-    }//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) {
-        boolean reCreateTriggers = false;
-        boolean skipV2 = false;
- 
-        if (oldVersion == 1) {
-            upgradeToV2(db);
-            skipV2 = true; // this upgrade including the upgrade from v2 to v3
-            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");
-        }
-    }//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
-        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 ''");
-        // 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);
-    }//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