Using Stream/Sink in Flutter

Question

I\'m trying to replace the increment flutter app code, by using Streams from Dart API without using scoped_model or rxdart.

So I read this and watched this,

Answer 1

Thanks a lot to vbandrade his answer helped me figuring t out. the solution worked with me is:

I need to have 2 StreamController if I need to listen to a sink in my bloc Business Logic Component, then process and stream the output to other elements.

The counter_bloc.dart is:

import 'dart:async';

class CounterBloc {
  int _count = 0;

  // The controller to stream the final output to the required StreamBuilder
  final _counter = StreamController.broadcast();
  Stream get counter => _counter.stream;

  // The controller to receive the input form the app elements     
  final _query = StreamController();
  Sink get query => _query.sink;
  Stream get result => _query.stream;

  // The business logic
  CounterBloc() {
    result.listen((increment) {     // Listen for incoming input         
      _count += increment;          // Process the required data
      _counter.add(_count);         // Stream the required output
    });
  }

  void dispose(){
    _query.close();
    _counter.close();
  }
}

And the main.dart is:

import 'counter_bloc.dart';
import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  State createState() {
    return _MyHomePageState();
  }

}

class _MyHomePageState extends State {
  var bloc = CounterBloc();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              'You have pushed the button this many times:',
            ),
            StreamBuilder(      // Listen to the final output sent from the Bloc
              stream: bloc.counter,
              initialData: 0,
              builder: (BuildContext c, AsyncSnapshot data) {
                return Text(
                  '${data.data}',
                  style: Theme.of(context).textTheme.display1,
                );
              },
            ),
          ],
        ),
      ),
      floatingActionButton: Row(
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          FloatingActionButton(
            onPressed: () {
              bloc.query.add(2);         // Send input to the Bloc
            },
            tooltip: 'Increment 2',
            child: Text("+2"),
          ),
          FloatingActionButton(
            onPressed: () {
              bloc.query.add(1);        // Send input to the Bloc
            },
            tooltip: 'Increment 1',
            child: Text("+1"),
          ),
        ],
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}