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doc/NotesDatabaseHelper.java
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王希宁 2023317170
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;
public class NotesDatabaseHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "note.db"; // 数据库名称
private static final int DB_VERSION = 4; // 数据库版本号
public interface TABLE {
public static final String NOTE = "note"; // 笔记表名称
public static final String DATA = "data"; // 数据表名称
}
private static final String TAG = "NotesDatabaseHelper"; // 日志标签
private static NotesDatabaseHelper mInstance; // 单例实例
private static final String CREATE_NOTE_TABLE_SQL = // 创建笔记表的SQL语句
"CREATE TABLE " + TABLE.NOTE + "(" +
NoteColumns.ID + " INTEGER PRIMARY KEY," +
// ... 省略其他字段
NoteColumns.VERSION + " INTEGER NOT NULL DEFAULT 0" +
")";
private static final String CREATE_DATA_TABLE_SQL = // 创建数据表的SQL语句
"CREATE TABLE " + TABLE.DATA + "(" +
DataColumns.ID + " INTEGER PRIMARY KEY," +
// ... 省略其他字段
DataColumns.DATA5 + " TEXT NOT NULL DEFAULT ''" +
")";
private static final String CREATE_DATA_NOTE_ID_INDEX_SQL = // 创建数据表的索引SQL语句
"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
*/
private static final String NOTE_INCREASE_FOLDER_COUNT_ON_UPDATE_TRIGGER = // 创建触发器的SQL语句
"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";
/**
* 其他代码...
*/
}
```
这里对数据库帮助类的各个部分进行了注释说明，包括数据库名称、版本号、表名称、创建表的SQL语句等。希望这样的注释能够帮助你更好地理解和使用这段代码。
```java
/**
* 当将笔记从文件夹中移出时，减少文件夹中的笔记数量
*/
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";
/**
* 将新笔记插入到文件夹中时，增加文件夹中的笔记数量
*/
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";
/**
* 当从文件夹中删除笔记时，减少文件夹中的笔记数量
*/
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";
/**
* 当插入类型为{@link DataConstants#NOTE}的数据时，更新笔记内容
*/
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";
/**
* 当类型为{@link DataConstants#NOTE}的数据发生更改时，更新
```java
/**
* 当数据类型为{@link DataConstants#NOTE}的数据被删除时，更新笔记内容
*/
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";
/**
* 删除已删除笔记所属的数据
*/
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";
/**
* 删除已删除文件夹所属的笔记
*/
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";
/**
* 将已移至回收站文件夹的文件夹中的笔记移至回收站
*/
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";
public NotesDatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
}
public void createNoteTable(SQLiteDatabase db) {
db.execSQL(CREATE_NOTE_TABLE_SQL);
reCreateNoteTableTriggers(db);
createSystemFolder(db);
Log.d(TAG, "note table has been created");
}
```
```java
/**
* 重新创建笔记表的触发器
* @param db SQLiteDatabase对象
*/
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
* @param db SQLiteDatabase对象
*/
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，即默认文件夹
*/
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，用于移动笔记
*/
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
*/
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 SQLiteDatabase对象
*/
public void createDataTable(SQLiteDatabase db) {
db.execSQL(CREATE_DATA_TABLE_SQL);
reCreateDataTableTriggers(db);
db.execSQL(CREATE_DATA_NOTE_ID_INDEX_SQL);
Log.d(TAG, "数据表已创建");
}
/**
* 重新创建数据表的触发器
* @param db SQLiteDatabase对象
*/
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NotesDatabaseHelper的实例
* @param context 上下文对象
* @return NotesDatabaseHelper的实例
*/
static synchronized NotesDatabaseHelper getInstance(Context
```java
/**
* 数据库升级方法
* @param db SQLiteDatabase对象
* @param oldVersion 旧版本号
* @param newVersion 新版本号
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
boolean reCreateTriggers = false;
boolean skipV2 = false;
if (oldVersion == 1) {
upgradeToV2(db);
skipV2 = true; // 此升级包括从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("升级笔记数据库到版本 " + newVersion
+ " 失败");
}
}
/**
* 升级到版本2的方法
* @param db SQLiteDatabase对象
*/
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);
}
/**
* 升级到版本3的方法
* @param db SQLiteDatabase对象
*/
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");
// 添加一个用于gtask id的列
db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.GTASK_ID
+ " TEXT NOT NULL DEFAULT ''");
// 添加一个垃圾箱系统文件夹
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的方法
* @param db SQLiteDatabase对象
*/
private void upgradeToV4(SQLiteDatabase db) {
db.execSQL("ALTER TABLE " + TABLE.NOTE + " ADD COLUMN " + NoteColumns.VERSION
+ " INTEGER NOT NULL DEFAULT 0");
}
```
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