flutter - Awesome_Notifications - 状态错误 : Stream has already been listened to

Question

我正在使用这个 flutter library来处理通知。在 initState()在我的 HomeView我初始化这个监听器:

_notificationsActionStreamSubscription = AwesomeNotifications().actionStream.listen((receivedNotification) {
  print("user tapped on notification " + receivedNotification.id.toString());
});

稍后当有人登录或退出我的应用程序时，我会调用这些行:

Navigator.of(context).popUntil((route) => route.isFirst);
Navigator.pushReplacement(context, MaterialPageRoute(builder: (_) => HomeView()));

这是 initState()我的 HomeView再次调用导致错误:

Bad state: Stream has already been listened to.

这就是为什么我在从上面调用两条 Navigator 行之前这样做了，但没有成功:

AwesomeNotifications().createdSink.close();
_notificationsActionStreamSubscription.cancel();

我究竟做错了什么？我取消了流订阅，为什么我仍然收到此错误消息？
谢谢你的建议!

Answer 1

您得到的错误不是由 _notificationsActionStreamSubscription 引起的.
如果你仔细阅读它说

Stream has already been listened to

这意味着可能 AwesomeNotifications().actionStream一次只能处理一个听众。 _notificationsActionStreamSubscription.cancel()似乎不起作用，可能是 AwesomeNotifications().actionStream不知道流监听器已关闭。
每次页面被推送时，它都会被重建，并且 AwesomeNotifications()抛出错误，因为它认为您正在附加第二个监听器。
所以我提出了这个解决方案: 移动 notificationsActionStreamSubscription到 HomeView 的父小部件.
在父级中创建实例，然后将其附加到 actionStream。
每次打电话 Navigator.pushReplacement 将其作为参数发送 .
首页查看 :(我把它变成了一个有状态的小部件)

class HomeView extends StatefulWidget {

  final StreamSubscription<ReceivedAction> notificationsActionStreamSubscription;
  const HomeView({Key key, @required this.notificationsActionStreamSubscription}) : super(key: key);
  
  @override
  _HomeViewState createState() => _HomeViewState();
}

class _HomeViewState extends State<HomeView> {

  //You can access with widget.notificationsActionStreamSubscription
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('HomeView '),
      ),
      body: Container(
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [],
            )
          ],
        ),
      ),
    );
  }
  
}

在您的父小部件中(我想它是一个有状态的小部件):

  StreamSubscription<ReceivedAction> notificationsActionStreamSubscription;

  @override
  void initState() {
    super.initState();
    notificationsActionStreamSubscription =
        AwesomeNotifications().actionStream.listen((receivedNotification) {
      print(
          "user tapped on notification " + receivedNotification.id.toString());
    });
  }

每次你推送 HomeView 时:

Navigator.of(context).popUntil((route) => route.isFirst);
Navigator.pushReplacement(context, MaterialPageRoute(builder: (_) => HomeView(notificationsActionStreamSubscription:
                    notificationsActionStreamSubscription)));

这样做， notificationsActionStreamSubscription不会被重建和附加到 AwesomeNotifications().actionStream每次推 HomeView .