android SQLiteOpenHelper 几个方法

1. public void onCreate(SQLiteDatabase db)

create table

2.public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)

已经存在的表升级操作

如加入列  alart 操作 事务批量操作

db.beginTransaction();
db.execSQL("ALTER TABLE favorites  ADD COLUMN appWidgetId INTEGER NOT NULL DEFAULT -1;");
db.setTransactionSuccessful();
db.endTransaction();

或者 重建新表删除旧的表

3.public void onOpen(SQLiteDatabase db)

Called when the database has been opened

4.

public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
throw new SQLiteException("Can‘t downgrade database from version " +
oldVersion + " to " + newVersion);
}

当新版本低于旧版本时候调用 抛出异常

5.public void onConfigure(SQLiteDatabase db) {}

db被配置时候调用 猜想是set name  版本好时候吧