Question 342597 in Flutter Question posted in
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Flutter – Riverpod : how to listen to an async stream provider

I have an async stream provider (details omitted for clarity – basically it delivers a stream of Strings):

final mqttStreamProvider = StreamProvider<String>((ref) async* {
  final wsClient = ref.watch(mqttClientProvider.future);
  final service = await wsClient;

  await for (final value in service.getMessageStream()) {
    yield value;
  }
});

My understanding is that the right way to handle messages that don’t result in a UI impact (no rebuild) is to use :
ref.listen(...)
in the build method of the top level widget of my application.

However, I can’t find any example on how to listen to an async stream provider.
Any help on how to do this much appreciated!

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    Well, just after asking the answer came :-)

    ref.listen(mqttStreamProvider, (prev, next) {
      print("new stream value $next");
    });

  2. 0

    You can watch for your StreamProvider inside the build method

    final steamAsync = ref.watch(mqttStreamProvider);

    and then you can use AsyncValue.when like this,

    return Scaffold(
  body: steamAsync.when(
    data: (data) {
      // return widget with data
    }
    error: (err, s) {
      // return error widget
    }
    loading: () {
      // return loading widget
    }
  ),
);

    I believe that in this way you can handle your error and loading state easily.

    Also, you can skip loading or error using,

    steamAsync.when(
  skipError: true,
  skipLoadingOnRefresh: true,
  skipLoadingOnReload: true,
  .
  .
  .
}
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