Flutter - 手动触发 StreamSubscription onData

Question

我在flutter中使用pedometer插件，我注意到的一件事是，当我在一段时间后打开应用程序时，显示的步数不会更新，直到我在打开应用程序时执行步骤以触发StreamSubscription 的 onData 方法。这不是setState 的问题，因为它每秒更新一次。

以下是我到目前为止所做的与此相关的部分内容：

class _MyScreenState extends State<MyScreen>
    with AutomaticKeepAliveClientMixin<Page1>, WidgetsBindingObserver {
  StreamSubscription _subscription;
  final Store<AppState> store;

  _MyScreenState(this.store, this.pedometer);

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    setUpPedometer();

}

  void setUpPedometer() {
    _subscription = pedometer.stepCountStream
        .listen(_onData, onError: _onError, cancelOnError: true);
  }

  @override
  Future<Null> didChangeAppLifecycleState(AppLifecycleState state) async {
    if (state == AppLifecycleState.resumed) {
      await resumeCallBack();
    }
  }

  resumeCallBack() {
     // here, I am looking for a way to trigger onData method
  }

  void _onData(int stepCountValue) async {
    print("stepCountValue : ${stepCountValue}");
    store.dispatch(UpdateStepsAction(
        steps: stepCountValue));
}

}

Answer 1

import 'dart:async';
import 'package:pedometer/pedometer.dart';

class PedometerController{
  static Future<int> getStepsFromPedometer() async{

    StreamController<int> streamHelper = new StreamController();
    var pedometer = Pedometer();
    pedometer.pedometerStream.listen((v){
      streamHelper.sink.add(v);
      streamHelper.close();
    });
    return await whenTrue(streamHelper.stream);
  }

  static Future<int> whenTrue(Stream<int> source) {
    return source.firstWhere((int item) => item > -1);
  }
}