在Flutter中使用Stream / Sink

2 回答

• -1

  不知道对rx_dart的限制，但我只能尝试使用它来回答 . 大声笑

  你的团队没有定义要在你的输入流中监听的东西，这就是我可以让它工作的方式

  counter_bloc.dart

  import 'package:rxdart/rxdart.dart';
  import 'dart:async';
  
  class CounterBloc {
    int _count = 0;
  
    ReplaySubject<int> _increment = ReplaySubject<int>();
    Sink<int> get increment => _increment;
  
    BehaviorSubject<int> _countStream = BehaviorSubject<int>(seedValue: 0);
    Stream<int> get count => _countStream.stream;
  
    CounterBloc() {
      _increment.listen((increment) {
        _count += increment;
        _countStream.add(_count);
      });
    }
  }
  

  在构造函数中，为该流设置listen方法 . 对于每个发送的增量，它将递增计数器并将当前计数发送到另一个流 .

  在 main.dart 中，删除了_counter属性，因为它现在由BLOC处理 . 并显示我使用了流构建器 .

  还增加了第二个晶圆厂，用2个增量来测试逻辑 .

  希望这可以帮助你模拟你的集团类 . :)

  一个好的集团参考：https://www.youtube.com/watch?v=PLHln7wHgPE

  main.dart

  import 'counter_bloc.dart';
  import 'package:flutter/material.dart';
  
  void main() => runApp(MyApp());
  
  class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage(title: 'Flutter Demo Home Page'),
      );
    }
  }
  
  class MyHomePage extends StatefulWidget {
    MyHomePage({Key key, this.title}) : super(key: key);
  
    final String title;
  
    @override
    _MyHomePageState createState() => _MyHomePageState();
  }
  
  class _MyHomePageState extends State<MyHomePage> {
    CounterBloc bloc = CounterBloc();
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
              StreamBuilder<int>(
                stream: bloc.count,
                initialData: 0,
                builder: (BuildContext c, AsyncSnapshot<int> data) {
                  return Text(
                    '${data.data}',
                    style: Theme.of(context).textTheme.display1,
                  );
                },
              ),
            ],
          ),
        ),
        floatingActionButton: Row(
          mainAxisAlignment: MainAxisAlignment.end,
          children: <Widget>[
            FloatingActionButton(
              onPressed: () {
                bloc.increment.add(2);
              },
              tooltip: 'Increment 2',
              child: Text("+2"),
            ),
            FloatingActionButton(
              onPressed: () {
                bloc.increment.add(1);
              },
              tooltip: 'Increment 1',
              child: Text("+1"),
            ),
          ],
        ), // This trailing comma makes auto-formatting nicer for build methods.
      );
    }
  }
  

  回复于 2024-05-19T04:43:26+08:00
• -1

  非常感谢vbandrade他的回答帮助我搞清楚了 . 与我合作的解决方案是：

  如果我需要在 bloc 业务逻辑组件中监听 sink ，然后处理并输出到其他元素，我需要2 StreamController .

  counter_bloc.dart 是：

  import 'dart:async';
  
  class CounterBloc {
    int _count = 0;
  
    // The controller to stream the final output to the required StreamBuilder
    final _counter = StreamController.broadcast<int>();
    Stream<int> get counter => _counter.stream;
  
    // The controller to receive the input form the app elements     
    final _query = StreamController<int>();
    Sink<int> get query => _query.sink;
    Stream<int> get result => _query.stream;
  
    // The business logic
    CounterBloc() {
      result.listen((increment) {     // Listen for incoming input         
        _count += increment;          // Process the required data
        _counter.add(_count);         // Stream the required output
      });
    }
  
    void dispose(){
      _query.close();
      _counter.close();
    }
  }
  

  main.dart 是：

  import 'counter_bloc.dart';
  import 'package:flutter/material.dart';
  
  void main() => runApp(MyApp());
  
  class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: MyHomePage(title: 'Flutter Demo Home Page'),
      );
    }
  }
  
  class MyHomePage extends StatefulWidget {
    MyHomePage({Key key, this.title}) : super(key: key);
  
    final String title;
  
    @override
    State<StatefulWidget> createState() {
      return _MyHomePageState();
    }
  
  }
  
  class _MyHomePageState extends State<MyHomePage> {
    var bloc = CounterBloc();
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text(widget.title),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'You have pushed the button this many times:',
              ),
              StreamBuilder<int>(      // Listen to the final output sent from the Bloc
                stream: bloc.counter,
                initialData: 0,
                builder: (BuildContext c, AsyncSnapshot<int> data) {
                  return Text(
                    '${data.data}',
                    style: Theme.of(context).textTheme.display1,
                  );
                },
              ),
            ],
          ),
        ),
        floatingActionButton: Row(
          mainAxisAlignment: MainAxisAlignment.end,
          children: <Widget>[
            FloatingActionButton(
              onPressed: () {
                bloc.query.add(2);         // Send input to the Bloc
              },
              tooltip: 'Increment 2',
              child: Text("+2"),
            ),
            FloatingActionButton(
              onPressed: () {
                bloc.query.add(1);        // Send input to the Bloc
              },
              tooltip: 'Increment 1',
              child: Text("+1"),
            ),
          ],
        ), // This trailing comma makes auto-formatting nicer for build methods.
      );
    }
  }
  

  回复于 2024-05-19T04:43:26+08:00