Question

我正在尝试使用Bloc模式获取sqlite表中一列的总和。

debt_bloc.dart

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Intent intent = new Intent(MainActivity.this, BackgroundService.class);
    startService(intent);



}

debt_dao.dart

private Handler mainHandler;
private RenderersFactory renderersFactory;
private BandwidthMeter bandwidthMeter;
private LoadControl loadControl;
private DataSource.Factory dataSourceFactory;
private ExtractorsFactory extractorsFactory;
private MediaSource mediaSource;
private TrackSelection.Factory trackSelectionFactory;
private SimpleExoPlayer player;
private final String streamUrl = "http://bbcwssc.ic.llnwd.net/stream/bbcwssc_mp1_ws-einws";
private TrackSelector trackSelector;

@Override
public void onCreate() {
    super.onCreate();
    startPlayer();
}

@Override
public IBinder onBind(Intent intent) {
    return null;
}

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    startPlayer();
    return START_STICKY;
}

@Override
public void onDestroy() {
    super.onDestroy();
}

public void startPlayer(){

    renderersFactory = new DefaultRenderersFactory(getApplicationContext());
    bandwidthMeter = new DefaultBandwidthMeter();
    trackSelectionFactory = new AdaptiveTrackSelection.Factory(bandwidthMeter);
    trackSelector = new DefaultTrackSelector(trackSelectionFactory);
    loadControl = new DefaultLoadControl();

    player = ExoPlayerFactory.newSimpleInstance(this, renderersFactory, trackSelector, loadControl);

    player.addListener(this);

    dataSourceFactory = new DefaultDataSourceFactory(getApplicationContext(), "ExoplayerDemo");
    extractorsFactory = new DefaultExtractorsFactory();
    mainHandler = new Handler();
    mediaSource = new ExtractorMediaSource(Uri.parse(streamUrl),
            dataSourceFactory,
            extractorsFactory,
            mainHandler,
            null);

    player.prepare(mediaSource);
}

debt_repositary.dart

getTotalAmount() async {
    return await _debtRepository.getTotalAmt();
  }

当我尝试如下打印时

 Future<int> getTotalAmount() async {
    final db = await dbProvider.database;

    var result = await db.rawQuery("SELECT SUM(amount) FROM $debtDetailsTable");
    int value = result[0]["SUM(amount)"];
    return value;
  }

添加新数据时输出未更新。但是，如果返回主屏幕并转到各自的屏幕，则该值正在更新。

请以正确的方式引导我。预先感谢

Answer 1

在打印之前先等待您的方法。

var total = await debtBloc.getTotalAmount(); // await here
print(total); // should now print some int value

在flutter中获取输出作为“'Future <dynamic>'的实例”

1 个答案: