颤动流以显示句柄可见状态

Question

[我有一个小部件isLive，它会根据块返回的值来更改状态。但是，每次我运行该应用程序时，我都会得到

getter'progressStateStream'被调用为null

我尝试遵循此answer

 Widget isLive() {
    return Container(
        child: StreamBuilder<bool>(
      stream: _bloc.progressStateStream,
      builder: (context, snapshot) {

        return Visibility(
          maintainState: true,
          visible: snapshot.data ?? false,
          child: ClipRRect(
            borderRadius: BorderRadius.all(Radius.circular(10)),
            child: Container(
              color: Colors.pink[50],
              height: 50,
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                children: <Widget>[

                  Text("yaay i'm visible"),

                  RaisedButton(
                    shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(20)),
                    child: Text(
                      "hide"
                    ),
                    color: Colors.white,
                    onPressed: () {
                      _bloc.changeProgressState(state: false);
                    },
                  )
                ],
              ),
            ),
          ),
        );
      },
    ));
  }

这是我的团体

  //this Subject allows sending data, error and done events to the listener
  final PublishSubject<bool> _progressStateSubject = new PublishSubject();

  //the listener are streaming on changes
  Observable<bool> get progressStateStream => _progressStateSubject.stream;

  //to change your progress state
  void changeProgressState({bool state}) => _progressStateSubject.sink.add(state);

此外，如果我想用水合集团保存国家，我将如何处理

Answer 1

通过将块添加到初始化状态通过将我的块初始化为初始化状态来修复它>

_bloc = RBloc();
 _bloc.progressStateStream;