检测是否执行了房间破坏性迁移

Question

如果我在启用破坏性回退的情况下运行 Room 迁移：

Room.databaseBuilder(applicationContext, MyDb::class.java, "database-name")
        .fallbackToDestructiveMigration()
        .build()

有没有办法确定破坏性迁移是否被触发与迁移是否成功完成？我希望能够记录一些信息以进行跟踪。

Answer 1

你可以使用Callback和add it to your database的房间，它有以下方法：你可以在哪里使用onDestructiveMigration

• onCreate:第一次创建数据库时调用
• onOpen: 打开数据库时触发
• onDestructiveMigration:数据库被破坏性迁移后调用

这是一个示例

@Database(entities = {.....}, version = 1)

public abstract class MyDatabase extends RoomDatabase {

    private static final String DATABASE_NAME = “myDatabaseName.db”;

    private static final Object LOCK = new Object();

    private static volatile MyDatabase instance; 

    public static MyDatabase getDatabase(final Context context) {
        if (INSTANCE == null) {
            synchronized (MyDatabase.class) {
                if (INSTANCE == null) {
                    // Create database here.
                    INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                            MyDatabase.class, DATABASE_NAME)
                            .fallbackToDestructiveMigration()
                            .addCallback(mCallback) // Trigger the callback
                            .build();
                }
            }
        }
        return INSTANCE;
    }


    /*
     * Callback when database is created & when it’s opened
     * */
    static RoomDatabase.Callback mCallback = new Callback() {
        @Override
        public void onCreate(@NonNull SupportSQLiteDatabase db) { // Callback when database is first-time created or recreated after destruction  
            super.onCreate(db);
            Log.i("LOG_TAG", “Database is created”);
        }

        @Override
        public void onOpen(@NonNull SupportSQLiteDatabase db) { // callback when the activity is opened 
            super.onOpen(db); 
            Log.i("LOG_TAG", “Database is opened”);  
        }
    };


        @Override
        public void onDestructiveMigration(@NonNull SupportSQLiteDatabase db) { // Called after the database was destructively migrated
            super.onDestructiveMigration(db);
            Log.i(LOG_TAG, “Database is destructed”);
        }

}