Flutter : Bad state: Stream has already been listened to

Question

    class MyPage extends StatelessWidget {
      @override
      Widget build(BuildContext context) {
        return Defaul         


        

Answer 1

In my case, I was getting this error because the same line of code myStream.listen() was being called twice in the same widget on the same stream. Apparently this is not allowed!

UPDATE: If you intend to subscribe to the same stream more than once, you may want to choose behavior subject instead:

final _myController = BehaviorSubject();
// use myStream.listen((latestEvent) {// run code when event is received});
Stream get myStream =>
      _myController.stream;
// use myStreamInputSink.add('new event'); to trigger events
Sink get mySteamInputSink => _myController.sink;

OR If a widget subscribes to a stream, and this widget is destroyed then redrawn which results for its new instance to subscribe to the same listener a second time, it's best to reset on widget dispose:

_flush() {
  _myController.close();
  _myController = StreamController();
}

Old Answer:

What fixed it for me is to both create a my stream controller as a broadcast stream controller:

var myStreamController = StreamController.broadcast();

AND

use stream as a broadcast stream:

myStreamController.stream.asBroadcastStream().listen(onData);