获取Room Persistence Library Android的onUpgrade（）回调

Question

如何在使用Room Persistence Library时升级数据库时获得回调？我提供了Migration类来在升级Database时在表中添加/删除一些列。

Answer 1

您需要提供下面提到的Room Database回调。

return Room.databaseBuilder(application, WalletDatabase.class, "wallet.db")
            .addMigrations(MIGRATION_1_3)
            .addMigrations(MIGRATION_2_3)
            .addCallback(callback)
            .build();

如下所述声明回调。

public static RoomDatabase.Callback callback = new RoomDatabase.Callback() {
    @Override
    public void onCreate(@NonNull SupportSQLiteDatabase db) {
        super.onCreate(db);
        //DO AS NEEDED
    }

    @Override
    public void onOpen(@NonNull SupportSQLiteDatabase db) {
        super.onOpen(db);
         //DO AS NEEDED
    }
};