CODEWITHSUNDEEP
dartflutterrxdartstream-builder
Alan Kałuża
Alan Kałuża

Reputation: 543

StreamBuilder is not rebuilding on new event in stream

My StreamBuilder in view:

Widget build(BuildContext context) {
    print("rebuilding..."); // as of now this gets called only on view initialization and never again - i.e. not on new events going through alarmController.stream

    return StreamBuilder(
        stream: widget.bloc.alarmController.stream,
        initialData: Alarm(''),
        builder: (BuildContext context, AsyncSnapshot<Alarm> snapshot) {
          if (!snapshot.hasData) {
            return Center(
              child: Text(StringLiterals.NO_ALARM_DATA_MSG))
            );
          }

          return Switch(
                  activeColor: Colors.red,
                  value: snapshot.data.status == 'Started',
                  onChanged: (bool _value) {
                    _newAlarmValue = _value;
                    _askAlarmConfirmation();
                  }));
        });
  }

meat of my bloc:

AlarmBloc(this.Api) {
    getAlarm();
}
  getAlarm() async {
    Alarm response = await Api.getAlarmStatus();
    alarmController.sink.add(response); // here im adding new event, therefore streambuilder should rebuild, right?
}

And lastly the code I call to initiate new event(in this case it's firebase message):

if(_message.notification.body.contains("Alarm") && IS_LOGGED_IN == true) {
   alarmBloc.getAlarm();
 }

So the problem is StreamBuilder not rebuilding whenever new event passes through alarmController.stream. What could be the reason?

Upvotes: 3

Views: 5254

Answers (2)

Alan Kałuża
Alan Kałuża

Reputation: 543

The issue was I was instantiaing my BLOC incorrectly(second one) and working on a second parallel stream and therefore not the one passed to StreamBuilder.

Upvotes: 1

Val
Val

Reputation: 1350

Your bloc needs to be a type of Stream. The same stream type as your StreamBuilder. For example your bloc needs to be a Stream<Alarm>. Otherwise stream: widget.bloc.alarmController.stream, will only be called once and won't act as an asynchronous stream of data.

Your Streambuilder needs to check for connection states

Widget build(BuildContext context) {
    print("rebuilding..."); // as of now this gets called only on view initialization and never again - i.e. not on new events going through alarmController.stream

    return StreamBuilder<Alarm>(
        stream: widget.bloc.alarmController.stream,
        initialData: Alarm(''),
        builder: (BuildContext context, AsyncSnapshot<Alarm> snapshot) {
          if (snapshot.hasError) return new Text('Error: ${snapshot.error}');
      switch (snapshot.connectionState) {
        case ConnectionState.waiting:
          return Text('Loading...'); 
        default: 
          if (!snapshot.hasData) {
             return Center(
                child: Text(StringLiterals.NO_ALARM_DATA_MSG))
             );
          }

         return Switch(
              activeColor: Colors.red,
              value: snapshot.data.status == 'Started',
              onChanged: (bool _value) {
                _newAlarmValue = _value;
                _askAlarmConfirmation();
              }));
      }

Here are the other types of connection states you can check for:

async.dart

    enum ConnectionState {
  /// Not currently connected to any asynchronous computation.
  ///
  /// For example, a [FutureBuilder] whose [FutureBuilder.future] is null.
  none,

  /// Connected to an asynchronous computation and awaiting interaction.
  waiting,

  /// Connected to an active asynchronous computation.
  ///
  /// For example, a [Stream] that has returned at least one value, but is not
  /// yet done.
  active,

  /// Connected to a terminated asynchronous computation.
  done,
}

Upvotes: 2

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