获取房间持久库Android的onupgrade()回调

Question

当数据库使用房间持久库时，如何升级数据库时如何获得回调？我提供了迁移类，以在升级数据库时将一些列添加到表中。

Answer 1

// customize SupportSQLiteOpenHelper.Factory 
public class DecoratedOpenHelperFactory implements SupportSQLiteOpenHelper.Factory {
    @NonNull
    private final SupportSQLiteOpenHelper.Factory delegate;
    @Nullable
    private final SupportSQLiteOpenHelper.Callback customListener;
    public DecoratedOpenHelperFactory(@NonNull SupportSQLiteOpenHelper.Factory factory, @Nullable SupportSQLiteOpenHelper.Callback customListener) {
        this.delegate = factory;
        this.customListener = customListener;
    }
    @Override
    public SupportSQLiteOpenHelper create(@NonNull SupportSQLiteOpenHelper.Configuration configuration) {
        final SupportSQLiteOpenHelper.Configuration sqliteConfig = SupportSQLiteOpenHelper.Configuration.builder(configuration.context)
                .name(configuration.name)
                .callback(new DecoratedCallback(configuration.callback, customListener))
                .build();
        return delegate.create(sqliteConfig);
    }
}
// customize SupportSQLiteOpenHelper.Callback
public class DecoratedCallback extends SupportSQLiteOpenHelper.Callback {
    @NonNull
    private final SupportSQLiteOpenHelper.Callback delegate;
    @Nullable
    private final SupportSQLiteOpenHelper.Callback customListener;
    public DecoratedCallback(@NonNull SupportSQLiteOpenHelper.Callback supportSqLiteOpenHelperCallback, @Nullable SupportSQLiteOpenHelper.Callback customListener) {
        super(supportSqLiteOpenHelperCallback.version);
        this.delegate = supportSqLiteOpenHelperCallback;
        this.customListener = customListener;
    }
    @Override
    public void onCreate(@Nullable SupportSQLiteDatabase db) {
        delegate.onCreate(db);
        Optional.ofNullable(customListener).ifPresent(customListener -> customListener.onCreate(db));
    }
    @Override
    public void onUpgrade(SupportSQLiteDatabase db, int oldVersion, int newVersion) {
        delegate.onUpgrade(db, oldVersion, newVersion);
        Optional.ofNullable(customListener).ifPresent(customListener -> customListener.onUpgrade(db, oldVersion, newVersion));
    }
    @Override
    public void onDowngrade(SupportSQLiteDatabase db, int oldVersion, int newVersion) {
        delegate.onDowngrade(db, oldVersion, newVersion);
        Optional.ofNullable(customListener).ifPresent(customListener -> customListener.onDowngrade(db, oldVersion, newVersion));
    }
    @Override
    public void onOpen(SupportSQLiteDatabase db) {
        delegate.onOpen(db);
        Optional.ofNullable(customListener).ifPresent(customListener -> customListener.onOpen(db));
    }
    @Override
    public void onCorruption(SupportSQLiteDatabase db) {
        Optional.ofNullable(customListener).ifPresent(customListener -> customListener.onCorruption(db));
    }
}

最后，您可以使用这样的房间：

Room.databaseBuilder(context, databaseName)
    .openHelperFactory(new DecoratedOpenHelperFactory(
        new FrameworkSQLiteOpenHelperFactory(), new SupportSQLiteOpenHelper.Callback() {
            @Override
            public void onCreate(SupportSQLiteDatabase db) {
            }
            @Override
            public void onUpgrade(SupportSQLiteDatabase db, int oldVersion, int newVersion) {
            }
            // etc
        }))
    .build();

Answer 2

您需要提供房间数据库回调，如下所述。

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

声明回调如下所述。

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
    }
};