Counter Bloc + Provider

main.dart

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:rxdart/rxdart.dart';

class CounterBloc {
  final _subject = BehaviorSubject<int>.seeded(0);

  ValueObservable<int> get counter => _subject;

  void increment() => _subject.value++;

  void dispose() => _subject.close();
}

void main() {
  runApp(
    StatefulProvider<CounterBloc>(
      valueBuilder: (context) => CounterBloc(),
      onDispose: (context, bloc) => bloc.dispose(),
      child: MyApp(),
    ),
  );
}

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

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

  final String title;

  @override
  Widget build(BuildContext context) {
    final bloc = Provider.of<CounterBloc>(context);

    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text('You have pushed the button this many times:'),
            StreamBuilder<Object>(
              initialData: bloc.counter.value,
              stream: bloc.counter,
              builder: (context, snapshot) {
                return Text(
                  '${snapshot.data}',
                  style: Theme.of(context).textTheme.display1,
                );
              },
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: bloc.increment,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}