BlocListener Notifications

bloc_a.dart

import 'package:bloc/bloc.dart';

class BlocA extends Bloc<BlocATriggered, BlocAState> {
  @override
  BlocAState get initialState => BlocAUninitialized();

  @override
  Stream<BlocAState> mapEventToState(BlocAEvent event) async* {
    if (event is BlocATriggered) {
      yield BlocALoading();
      Future.delayed(Duration(seconds: 1));
      yield BlocASucceed();
    }
  }
}

abstract class BlocAEvent {}

class BlocATriggered extends BlocAEvent {}

abstract class BlocAState {}

class BlocAUninitialized extends BlocAState {
  @override
  String toString() {
    return 'BlocAUninitialized{}';
  }
}

class BlocALoading extends BlocAState {}

class BlocASucceed extends BlocAState {
  @override
  String toString() {
    return 'BlocASucceed{}';
  }
}

bloc_b.dart

import 'package:bloc/bloc.dart';

class BlocB extends Bloc<BlocBTriggered, BlocBState> {
  @override
  BlocBState get initialState => BlocBUninitialized();

  @override
  Stream<BlocBState> mapEventToState(BlocBEvent event) async* {
    if (event is BlocBTriggered) {
      yield BlocBLoading();
      Future.delayed(Duration(seconds: 1));
      yield BlocBSucceed();
    }
  }
}

abstract class BlocBEvent {}

class BlocBTriggered extends BlocBEvent {}

abstract class BlocBState {}

class BlocBLoading extends BlocBState {
  @override
  String toString() {
    return 'BlocBLoading{}';
  }
}

class BlocBUninitialized extends BlocBState {
  @override
  String toString() {
    return 'BlocBSucceed{}';
  }
}

class BlocBSucceed extends BlocBState {
  @override
  String toString() {
    return 'BlocBSucceed{}';
  }
}

main.dart

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

import 'bloc_a.dart';
import 'bloc_b.dart';
import 'main_page.dart';

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

class MyApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  // This widget is the root of your application.
  BlocA blocA;
  BlocB blocB;

  @override
  void initState() {
    super.initState();

    blocA = BlocA();
    blocB = BlocB();
  }

  @override
  void dispose() {
    super.dispose();
    blocA.dispose();
    blocB.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Snackbar Test',
      theme: ThemeData(),
      home: BlocProviderTree(
        blocProviders: [
          BlocProvider<BlocA>(bloc: blocA),
          BlocProvider<BlocB>(bloc: blocB),
        ],
        child: MainPage(),
      ),
    );
  }
}

main_page.dart

import 'package:flutter/material.dart';

import 'page_a.dart';
import 'page_b.dart';

class MainPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() => _MainPageState();
}

class _MainPageState extends State<MainPage> {
  int _activeBody = 0;
  final _widgetOptions = [
    PageA(),
    PageB(),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: _widgetOptions.elementAt(_activeBody),
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _activeBody,
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.cloud_done),
            title: Text('A'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.all_inclusive),
            title: Text('B'),
          )
        ],
        onTap: _onItemSelected,
      ),
    );
  }

  void _onItemSelected(int value) {
    setState(() {
      _activeBody = value;
    });
  }
}

page_a.dart

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

import 'bloc_a.dart';

class PageA extends StatelessWidget {
  final String _tag = 'PageA';

  @override
  Widget build(BuildContext context) {
    print('$_tag:build');
    BlocA blocA = BlocProvider.of<BlocA>(context);

    return BlocListener(
      bloc: blocA,
      listener: (BuildContext context, BlocAState state) {
        if (state is BlocASucceed) {
          Scaffold.of(context).showSnackBar(SnackBar(
            content: Text('${state.toString()}'),
          ));
        }
      },
      child: Center(
        child: FlatButton(
          child: Text('Trigger Bloc A'),
          onPressed: () => blocA.dispatch(BlocATriggered()),
        ),
      ),
    );
  }
}

page_b.dart

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

import 'bloc_b.dart';

class PageB extends StatelessWidget {
  final String _tag = 'PageB';

  @override
  Widget build(BuildContext context) {
    print('$_tag:build');
    BlocB blocB = BlocProvider.of<BlocB>(context);

    return BlocListener(
      bloc: blocB,
      listener: (BuildContext context, BlocBState state) {
        if (state is BlocBSucceed) {
          Scaffold.of(context).showSnackBar(SnackBar(
            content: Text('${state.toString()}'),
          ));
        }
      },
      child: Center(
        child: FlatButton(
          child: Text('Trigger Bloc B'),
          onPressed: () => blocB.dispatch(BlocBTriggered()),
        ),
      ),
    );
  }
}

pubspec.yaml

name: bloc_listener_test
description: A new Flutter project.

version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  flutter_bloc: ^0.11.1

dev_dependencies:
  flutter_test:
    sdk: flutter
    
flutter:
  uses-material-design: true