Type : INTEGER (long)
*/ 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 @@ -239,6 +257,7 @@ public class Notes { *Type: TEXT
*/ 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 { @@ -255,6 +274,7 @@ public class Notes { 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 { @@ -275,5 +295,6 @@ public class Notes { 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 } } diff --git a/MiNote/src/net/micode/notes/data/NotesDatabaseHelper.java b/MiNote/src/net/micode/notes/data/NotesDatabaseHelper.java index ffe5d57..adb427a 100644 --- a/MiNote/src/net/micode/notes/data/NotesDatabaseHelper.java +++ b/MiNote/src/net/micode/notes/data/NotesDatabaseHelper.java @@ -15,24 +15,35 @@ */ package net.micode.notes.data; - +//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.ContentValues; +//加载和访问资源。 import android.content.Context; +//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.SQLiteDatabase; +//用来管理数据的创建和版本更新 import android.database.sqlite.SQLiteOpenHelper; import android.util.Log; import net.micode.notes.data.Notes.DataColumns; import net.micode.notes.data.Notes.DataConstants; import net.micode.notes.data.Notes.NoteColumns; +//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 String DB_NAME = "note.db"; + /** + * 数据库版本号 + */ private static final int DB_VERSION = 4; - public interface TABLE { + /** + * 表名常量 + */ + 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"; @@ -42,6 +53,9 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { private static NotesDatabaseHelper mInstance; + /** + * 创建NOTE表的SQL语句 + */ private static final String CREATE_NOTE_TABLE_SQL = "CREATE TABLE " + TABLE.NOTE + "(" + NoteColumns.ID + " INTEGER PRIMARY KEY," + @@ -61,7 +75,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { 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 + "(" + @@ -76,7 +90,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { 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 " + @@ -92,7 +106,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " UPDATE " + TABLE.NOTE + " SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" + " WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" + - " END"; + " 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 @@ -105,7 +119,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" + " WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID + " AND " + NoteColumns.NOTES_COUNT + ">0" + ";" + - " END"; + " 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 @@ -117,7 +131,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " UPDATE " + TABLE.NOTE + " SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + " + 1" + " WHERE " + NoteColumns.ID + "=new." + NoteColumns.PARENT_ID + ";" + - " END"; + " 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 @@ -130,7 +144,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " SET " + NoteColumns.NOTES_COUNT + "=" + NoteColumns.NOTES_COUNT + "-1" + " WHERE " + NoteColumns.ID + "=old." + NoteColumns.PARENT_ID + " AND " + NoteColumns.NOTES_COUNT + ">0;" + - " END"; + " 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} @@ -143,7 +157,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " UPDATE " + TABLE.NOTE + " SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT + " WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" + - " END"; + " 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 @@ -156,7 +170,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " UPDATE " + TABLE.NOTE + " SET " + NoteColumns.SNIPPET + "=new." + DataColumns.CONTENT + " WHERE " + NoteColumns.ID + "=new." + DataColumns.NOTE_ID + ";" + - " END"; + " 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 @@ -169,7 +183,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " UPDATE " + TABLE.NOTE + " SET " + NoteColumns.SNIPPET + "=''" + " WHERE " + NoteColumns.ID + "=old." + DataColumns.NOTE_ID + ";" + - " END"; + " 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 @@ -180,7 +194,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " BEGIN" + " DELETE FROM " + TABLE.DATA + " WHERE " + DataColumns.NOTE_ID + "=old." + NoteColumns.ID + ";" + - " END"; + " 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 @@ -191,7 +205,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " BEGIN" + " DELETE FROM " + TABLE.NOTE + " WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" + - " END"; + " 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 @@ -204,18 +218,18 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { " UPDATE " + TABLE.NOTE + " SET " + NoteColumns.PARENT_ID + "=" + Notes.ID_TRASH_FOLER + " WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" + - " END"; + " 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"); @@ -234,6 +248,8 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { 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 +284,14 @@ 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 +301,23 @@ 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; - } + }//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) { @@ -331,6 +350,7 @@ 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) { @@ -338,6 +358,7 @@ public class NotesDatabaseHelper extends SQLiteOpenHelper { db.execSQL("DROP TABLE IF EXISTS " + TABLE.DATA); createNoteTable(db); createDataTable(db); + //更新到V2版本 } private void upgradeToV3(SQLiteDatabase db) { @@ -353,10 +374,12 @@ 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 }