陈念焯注释

src/net/micode/notes/data/NotesDatabaseHelper.java

@@ -14,7 +14,9 @@
  * limitations under the License.
  */
 
-package net.micode.notes.data;
+ //这个类是整个笔记应用的数据存储核心，负责数据库的创建、维护和升级，确保数据的一致性和完整性。
+
+package net.micode.notes.data;//导入包
 
 import android.content.ContentValues;
 import android.content.Context;
@@ -26,64 +28,81 @@ import net.micode.notes.data.Notes.DataColumns;
 import net.micode.notes.data.Notes.DataConstants;
 import net.micode.notes.data.Notes.NoteColumns;
 
-
+/**
+ * 笔记应用的数据库帮助类，负责数据库的创建和版本管理
+ */
 public class NotesDatabaseHelper extends SQLiteOpenHelper {
+    // 数据库名称常量
     private static final String DB_NAME = "note.db";
-
+    // 数据库版本号
     private static final int DB_VERSION = 4;
 
+    /**
+     * 数据库表名常量接口
+     */
     public interface TABLE {
+        // 笔记表名
         public static final String NOTE = "note";
-
+        // 数据表名
         public static final String DATA = "data";
     }
 
+    // 日志标签
     private static final String TAG = "NotesDatabaseHelper";
-
+    // 单例实例
     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.ID + " INTEGER PRIMARY KEY," +                     // 笔记ID
-            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +     // 父文件夹ID
-            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.ALERTED_DATE + " INTEGER NOT NULL DEFAULT 0," +   // 提醒日期
-            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.BG_COLOR_ID + " INTEGER NOT NULL DEFAULT 0," +    // 背景颜色ID
-            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期
-            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.HAS_ATTACHMENT + " INTEGER NOT NULL DEFAULT 0," + // 是否有附件
-            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期
-            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.NOTES_COUNT + " INTEGER NOT NULL DEFAULT 0," +    // 包含笔记数量(对文件夹)
-            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +
+            NoteColumns.SNIPPET + " TEXT NOT NULL DEFAULT ''," +          // 内容摘要
-            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.TYPE + " INTEGER NOT NULL DEFAULT 0," +           // 类型(笔记/文件夹)
-            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.WIDGET_ID + " INTEGER NOT NULL DEFAULT 0," +      // 小部件ID
-            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +
+            NoteColumns.WIDGET_TYPE + " INTEGER NOT NULL DEFAULT -1," +   // 小部件类型
-            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.SYNC_ID + " INTEGER NOT NULL DEFAULT 0," +       // 同步ID
-            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.LOCAL_MODIFIED + " INTEGER NOT NULL DEFAULT 0," + // 本地修改标记
-            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," +
+            NoteColumns.ORIGIN_PARENT_ID + " INTEGER NOT NULL DEFAULT 0," + // 原始父ID
-            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +
+            NoteColumns.GTASK_ID + " TEXT NOT NULL DEFAULT ''," +        // Google任务ID
-            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +
+            NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +        // 版本号
         ")";
 
+    /**
+     * 创建数据表的SQL语句
+     */
     private static final String CREATE_DATA_TABLE_SQL =
         "CREATE TABLE " + TABLE.DATA + "(" +
-            DataColumns.ID + " INTEGER PRIMARY KEY," +
+            DataColumns.ID + " INTEGER PRIMARY KEY," +                   // 数据ID
-            DataColumns.MIME_TYPE + " TEXT NOT NULL," +
+            DataColumns.MIME_TYPE + " TEXT NOT NULL," +                  // MIME类型
-            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +
+            DataColumns.NOTE_ID + " INTEGER NOT NULL DEFAULT 0," +       // 关联的笔记ID
-            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.CREATED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 创建日期
-            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," +
+            NoteColumns.MODIFIED_DATE + " INTEGER NOT NULL DEFAULT (strftime('%s','now') * 1000)," + // 修改日期
-            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.CONTENT + " TEXT NOT NULL DEFAULT ''," +         // 内容
-            DataColumns.DATA1 + " INTEGER," +
+            DataColumns.DATA1 + " INTEGER," +                            // 数据字段1(整型)
-            DataColumns.DATA2 + " INTEGER," +
+            DataColumns.DATA2 + " INTEGER," +                            // 数据字段2(整型)
-            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA3 + " TEXT NOT NULL DEFAULT ''," +           // 数据字段3(文本)
-            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +
+            DataColumns.DATA4 + " TEXT NOT NULL DEFAULT ''," +           // 数据字段4(文本)
-            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
+            DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +            // 数据字段5(文本)
         ")";
 
+    /**
+     * 在数据表上创建笔记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 + ");";
 
     /**
-     * Increase folder's note count when move note to the folder
+     * 触发器：当更新笔记的父文件夹ID时，增加新文件夹的笔记计数
      */
     private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
         "CREATE TRIGGER increase_folder_count_on_update "+
@@ -95,7 +114,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Decrease folder's note count when move note from folder
+     * 触发器：当更新笔记的父文件夹ID时，减少旧文件夹的笔记计数
      */
     private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
         "CREATE TRIGGER decrease_folder_count_on_update " +
@@ -108,7 +127,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Increase folder's note count when insert new note to the folder
+     * 触发器：当插入新笔记时，增加父文件夹的笔记计数
      */
     private static final String NOTE_INCREASE_FOLDER_COUNT_ON_INSERT_TRIGGER =
         "CREATE TRIGGER increase_folder_count_on_insert " +
@@ -120,7 +139,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Decrease folder's note count when delete note from the folder
+     * 触发器：当删除笔记时，减少父文件夹的笔记计数
      */
     private static final String NOTE_DECREASE_FOLDER_COUNT_ON_DELETE_TRIGGER =
         "CREATE TRIGGER decrease_folder_count_on_delete " +
@@ -133,7 +152,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Update note's content when insert data with type {@link DataConstants#NOTE}
+     * 触发器：当插入笔记数据时，更新笔记的内容摘要
      */
     private static final String DATA_UPDATE_NOTE_CONTENT_ON_INSERT_TRIGGER =
         "CREATE TRIGGER update_note_content_on_insert " +
@@ -146,7 +165,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Update note's content when data with {@link DataConstants#NOTE} type has changed
+     * 触发器：当更新笔记数据时，更新笔记的内容摘要
      */
     private static final String DATA_UPDATE_NOTE_CONTENT_ON_UPDATE_TRIGGER =
         "CREATE TRIGGER update_note_content_on_update " +
@@ -159,7 +178,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Update note's content when data with {@link DataConstants#NOTE} type has deleted
+     * 触发器：当删除笔记数据时，清空笔记的内容摘要
      */
     private static final String DATA_UPDATE_NOTE_CONTENT_ON_DELETE_TRIGGER =
         "CREATE TRIGGER update_note_content_on_delete " +
@@ -172,7 +191,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Delete datas belong to note which has been deleted
+     * 触发器：当删除笔记时，删除关联的数据
      */
     private static final String NOTE_DELETE_DATA_ON_DELETE_TRIGGER =
         "CREATE TRIGGER delete_data_on_delete " +
@@ -183,7 +202,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Delete notes belong to folder which has been deleted
+     * 触发器：当删除文件夹时，删除该文件夹下的所有笔记
      */
     private static final String FOLDER_DELETE_NOTES_ON_DELETE_TRIGGER =
         "CREATE TRIGGER folder_delete_notes_on_delete " +
@@ -194,7 +213,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         " END";
 
     /**
-     * Move notes belong to folder which has been moved to trash folder
+     * 触发器：当文件夹被移动到回收站时，将其下的所有笔记也移动到回收站
      */
     private static final String FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER =
         "CREATE TRIGGER folder_move_notes_on_trash " +
@@ -206,10 +225,18 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         "  WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
         " END";
 
+    /**
+     * 构造方法
+     * @param context 上下文对象
+     */
     public NotesDatabaseHelper(Context context) {
         super(context, DB_NAME, null, DB_VERSION);
     }
 
+    /**
+     * 创建笔记表
+     * @param db SQLite数据库对象
+     */
     public void createNoteTable(SQLiteDatabase db) {
         db.execSQL(CREATE_NOTE_TABLE_SQL);
         reCreateNoteTableTriggers(db);
@@ -217,7 +244,12 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         Log.d(TAG, "note table has been created");
     }
 
+    /**
+     * 重新创建笔记表相关的触发器
+     * @param db SQLite数据库对象
+     */
     private void reCreateNoteTableTriggers(SQLiteDatabase db) {
+        // 先删除可能存在的旧触发器
         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");
@@ -226,6 +258,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         db.execSQL("DROP TRIGGER IF EXISTS folder_delete_notes_on_delete");
         db.execSQL("DROP TRIGGER IF EXISTS folder_move_notes_on_trash");
 
+        // 创建新的触发器
         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);
@@ -235,41 +268,41 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         db.execSQL(FOLDER_MOVE_NOTES_ON_TRASH_TRIGGER);
     }
 
+    /**
+     * 创建系统文件夹
+     * @param db SQLite数据库对象
+     */
     private void createSystemFolder(SQLiteDatabase db) {
         ContentValues values = new ContentValues();
 
-        /**
+        // 创建通话记录文件夹
-         * 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);
 
-        /**
+        // 创建根文件夹
-         * 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);
 
-        /**
+        // 创建临时文件夹
-         * 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);
 
-        /**
+        // 创建回收站文件夹
-         * create trash folder
-         */
         values.clear();
         values.put(NoteColumns.ID, Notes.ID_TRASH_FOLER);
         values.put(NoteColumns.TYPE, Notes.TYPE_SYSTEM);
         db.insert(TABLE.NOTE, null, values);
     }
 
+    /**
+     * 创建数据表
+     * @param db SQLite数据库对象
+     */
     public void createDataTable(SQLiteDatabase db) {
         db.execSQL(CREATE_DATA_TABLE_SQL);
         reCreateDataTableTriggers(db);
@@ -277,16 +310,27 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         Log.d(TAG, "data table has been created");
     }
 
+    /**
+     * 重新创建数据表相关的触发器
+     * @param db SQLite数据库对象
+     */
     private void reCreateDataTableTriggers(SQLiteDatabase db) {
+        // 先删除可能存在的旧触发器
         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");
 
+        // 创建新的触发器
         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);
     }
 
+    /**
+     * 获取单例实例
+     * @param context 上下文对象
+     * @return NotesDatabaseHelper实例
+     */
     static synchronized NotesDatabaseHelper getInstance(Context context) {
         if (mInstance == null) {
             mInstance = new NotesDatabaseHelper(context);
@@ -296,6 +340,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
 
     @Override
     public void onCreate(SQLiteDatabase db) {
+        // 创建数据库时调用，创建笔记表和数据表
         createNoteTable(db);
         createDataTable(db);
     }
@@ -305,34 +350,43 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         boolean reCreateTriggers = false;
         boolean skipV2 = false;
 
+        // 从版本1升级到版本2
         if (oldVersion == 1) {
             upgradeToV2(db);
-            skipV2 = true; // this upgrade including the upgrade from v2 to v3
+            skipV2 = true; // 这个升级包含从v2到v3的升级
             oldVersion++;
         }
 
+        // 从版本2升级到版本3
         if (oldVersion == 2 && !skipV2) {
             upgradeToV3(db);
             reCreateTriggers = true;
             oldVersion++;
         }
 
+        // 从版本3升级到版本4
         if (oldVersion == 3) {
             upgradeToV4(db);
             oldVersion++;
         }
 
+        // 如果需要，重新创建触发器
         if (reCreateTriggers) {
             reCreateNoteTableTriggers(db);
             reCreateDataTableTriggers(db);
         }
 
+        // 检查版本升级是否完成
         if (oldVersion != newVersion) {
             throw new IllegalStateException("Upgrade notes database to version " + newVersion
                     + "fails");
         }
     }
 
+    /**
+     * 升级到版本2：重建所有表
+     * @param db SQLite数据库对象
+     */
     private void upgradeToV2(SQLiteDatabase db) {
         db.execSQL("DROP TABLE IF EXISTS " + TABLE.NOTE);
         db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA);
@@ -340,23 +394,36 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper {
         createDataTable(db);
     }
 
+    /**
+     * 升级到版本3：
+     * 1. 删除不再使用的触发器
+     * 2. 添加gtask_id列
+     * 3. 添加回收站系统文件夹
+     * @param db SQLite数据库对象
+     */
     private void upgradeToV3(SQLiteDatabase db) {
-        // drop unused triggers
+        // 删除不再使用的触发器
         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");
-        // add a column for gtask id
+        
+        // 添加gtask_id列
         db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
                 + " TEXT NOT NULL DEFAULT ''");
-        // add a trash system folder
+        
+        // 添加回收站系统文件夹
         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);
     }
 
+    /**
+     * 升级到版本4：添加version列
+     * @param db SQLite数据库对象
+     */
     private void upgradeToV4(SQLiteDatabase db) {
         db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
                 + " INTEGER NOT NULL DEFAULT 0");
     }
-}
+}