Call method outside stateful widget to update UI with flutter Bloc

Question

I have implemented a countetEvent and counterBloc:

abstract class CounterEvent {}

class IncrementEvent extends CounterEvent {}

class DecrementEvent extends CounterEvent {}

and counterBloc:

import 'dart:async';
import 'counter_event.dart';

class CounterBloc {
int _counter = 0;

final _counterStateController = StreamController<int>();
StreamSink<int> get _inCounter => _counterStateController.sink;
Stream<int> get counter => _counterStateController.stream;

final _counterEventController = StreamController<CounterEvent>();
Sink<CounterEvent> get counterEventSink => _counterEventController.sink;

CounterBloc() {
_counterEventController.stream.listen(_mapEventToState);
} 

void _mapEventToState(CounterEvent event) {
if (event is IncrementEvent)
  _counter++;
else
  _counter--;

_inCounter.add(_counter);
}

void dispose() {
_counterStateController.close();
_counterEventController.close();
}

}

and in My main.dart I have declared:

  final _bloc = CounterBloc();

I have two buttons one to increment and one for drecrement. the decrement works just find when using it in the main.dart file like soo:

    RaisedButton(
                    onPressed: () =>
                        _bloc.counterEventSink.add(DecrementEvent()),
                    child: Text("Minus"),
                  )

This will update the variable in the bloc and also the widget. But for the increment, when I call it from outside of the main.dart with a function it increment the value in the bloc but the UI doesn't update. This is how I implement it:

children: [
                  Button(), /// A stateful widget that returns a button
                  RaisedButton(
                    onPressed: () =>
                        _bloc.counterEventSink.add(DecrementEvent()),
                    child: Text("Minus"),
                  ),
                ],

This is the button class:


class Button extends StatefulWidget {
  @override
  _ButtonState createState() => _ButtonState();
}

class _ButtonState extends State<Button> {
  final _bloc = CounterBloc();

  @override
  Widget build(BuildContext context) {
    return Container(
      child: RaisedButton(
        onPressed: () => _bloc.counterEventSink.add(IncrementEvent()),
        child: Text("Add"),
      ),
    );
  }
}

How can I use the bloc events outside of the widget and update the UI? Or simply put, how can I update a stateful widget from another class.

w461 w461 · Accepted Answer · 2020-10-06T21:36:37

This solution of mine might answer your question. That's how I solved some communication issues between different blocks. You can also look-up inherited widgets, however, I haven't tried this, yet.

Call method outside stateful widget to update UI with flutter Bloc

1 Answers