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TeamProject/doc/精读代码(注释)/孔维屿注释/data/NotesDatabaseHelper.java

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/*
* 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.util.Log;
import net.micode.notes.data.Notes.DataColumns;
import net.micode.notes.data.Notes.DataConstants;
import net.micode.notes.data.Notes.NoteColumns;
/**
* 用于打开、创建和管理Note应用程序的数据库
*/
public class NotesDatabaseHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "note.db";
private static final int DB_VERSION = 4;
/**
* 这是一个接口,内部定义了一个笔记表和一个数据表的表名常量。
*/
public interface TABLE {
public static final String NOTE = "note";
public static final String DATA = "data";
}
private static final String TAG = "NotesDatabaseHelper";
private static NotesDatabaseHelper mInstance;
/**
* 该字符串表示用于创建“note”表的SQL语句。该表用于存储笔记的基本信息。
*/
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" +
")";
/**
* SQL语句用于创建“data”表的字符串常量
*/
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 ''" +
")";
/**
* SQL语句在"data"表上创建索引的字符串常量
*/
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
* 在将笔记移动到文件夹时增加文件夹的笔记计数
*/
private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
"CREATE TRIGGER increase_folder_count_on_update "+
" 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";
/**
* Decrease folder's note count when move note from folder
* 在将笔记移出文件夹时减少文件夹的笔记计数
*/
private static final String NOTE_DECREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER =
"CREATE TRIGGER decrease_folder_count_on_update " +
" 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";
/**
* Increase folder's note count when insert new note to the folder
* 此触发器将在向数据库中添加新的笔记时自动触发。当向某个文件夹添加新的笔记时此触发器将使该文件夹的“notes_count”值增加 1。
*/
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";
/**
* Decrease folder's note count when delete note from the folder
* 此触发器将在从数据库中删除笔记时自动触发。当从某个文件夹删除笔记时此触发器将使该文件夹的“notes_count”值减少 1。
*/
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";
/**
* Update note's content when insert data with type {@link DataConstants#NOTE}
* 此触发器将在向数据库中添加一个数据记录时自动触发。
* 当添加类型为“note”的数据记录时此触发器将更新笔记的“snippet”列将其设置为新增数据记录的“content”列值。
*/
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";
/**
* Update note's content when data with {@link DataConstants#NOTE} type has changed
* 此触发器将在数据库中的数据记录被更新时自动触发。
* 当更新的数据记录类型为“note”时此触发器将更新笔记的“snippet”列将其设置为更新后的数据记录的“content”列的值。
*/
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";
/**
* Update note's content when data with {@link DataConstants#NOTE} type has deleted
* 此触发器将在从数据库中删除一个数据记录时自动触发。
* 当被删除的数据记录类型为“note”时此触发器将更新笔记的“snippet”列并将其设置为空字符串。
*/
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";
/**
* Delete datas belong to note which has been deleted
* 此触发器将在从数据库中删除笔记时自动触发。它将删除与被删除笔记相关联的所有数据记录。
*/
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";
/**
* Delete notes belong to folder which has been deleted
* 此触发器将在从数据库中删除文件夹时自动触发,它将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 " +
" AFTER DELETE ON " + TABLE.NOTE +
" BEGIN" +
" DELETE FROM " + TABLE.NOTE +
" WHERE " + NoteColumns.PARENT_ID + "=old." + NoteColumns.ID + ";" +
" END";
/**
* Move notes belong to folder which has been moved to trash folder
* 此触发器将在将某个文件夹移动到回收站时自动触发,它会将该文件夹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 " +
" 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";
/**
* 这是 NotesDatabaseHelper 类的构造函数,用于创建数据库,并将数据库名称、版本等参数传递给基类 SQLiteOpenHelper 的构造函数。
* @param context
*/
public NotesDatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
/**
* 此方法用于在给定的 SQLiteDatabase 对象上创建“note”表。
* 它执行 CREATE_NOTE_TABLE_SQL 常量中指定的 SQL 语句,
* 并调用 reCreateNoteTableTriggers 和 createSystemFolder 方法以重置触发器并创建系统文件夹。
* @param db
*/
public void createNoteTable(SQLiteDatabase db) {
db.execSQL(CREATE_NOTE_TABLE_SQL);
reCreateNoteTableTriggers(db);
createSystemFolder(db);
Log.d(TAG, "note table has been created");
}
/**
* 此私有方法用于重置所有触发器,即在调用此方法之前删除所有现有的触发器,然后重新创建所有触发器。
* @param db
*/
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);
}
/**
* 此私有方法用于向数据库中插入四个系统文件夹。
* 它通过为每个文件夹创建一个 ContentValues 对象来添加数据,并将其插入名为 "note" 的数据库表中。
* 其中,每个文件夹具有唯一的 ID类型为 TYPE_SYSTEM。
* @param db
*/
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);
}
/**
* 此方法用于创建数据表。
* 它执行 CREATE_DATA_TABLE_SQL 常量中指定的 SQL 语句,并调用 reCreateDataTableTriggers 方法以重置触发器。
* 最后,它还创建了 CREATE_DATA_NOTE_ID_INDEX_SQL 常量中指定的 ID 索引。
* @param db
*/
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");
}
/**
* 用于重置增删改触发器,删除所有现有的触发器,然后重新创建触发器。
* @param db
*/
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);
}
/**
* 此方法是 NotesDatabaseHelper 类的静态方法,通过传递上下文对象来获取数据库的实例。
* 它将确保在多线程环境中只有一个实例创建。
* @param context
* @return
*/
static synchronized NotesDatabaseHelper getInstance(Context context) {
if (mInstance == null) {
mInstance = new NotesDatabaseHelper(context);
}
return mInstance;
}
/**
* 数据库被第一次创建时,此方法将调用。
* createNoteTable() 和 createDataTable() 两个方法将被调用,用于创建表和触发器。
* @param db
*/
@Override
public void onCreate(SQLiteDatabase db) {
createNoteTable(db);
createDataTable(db);
}
/**
* 当数据库需要更新到一个新版本时,此方法将被调用。
* 它通过指定旧版本和新版本号来确定进行哪些更新,
* 每个更新都会调用 upgradeToV2()、upgradeToV3() 和 upgradeToV4() 方法之一,以升级数据库结构。
* @param db
* @param oldVersion
* @param newVersion
*/
@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");
}
}
/**
* 此方法执行从 v1 升级到 v2 的数据迁移。它首先删除原来的表,然后创建新表,重新建立触发器。
* @param db
*/
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);
}
/**
* 此方法执行从 v2 升级到 v3 的数据迁移。
* 它删除不再需要的触发器并添加新的 note Gtask Id 列,以便允许在 Google Tasks 中同步任务到笔记应用程序中。
* @param db
*/
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);
}
/**
* 此方法执行从 v3 升级到 v4 的数据迁移。它为 notes 表添加了版本号列,以便在后续升级中进行版本验证。
* @param db
*/
private void upgradeToV4(SQLiteDatabase db) {
db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
+ " INTEGER NOT NULL DEFAULT 0");
}
}