hydrated_bloc 6.0.0-dev.4

An extension to the bloc state management library which automatically persists and restores bloc states.

example/lib/main.dart

import 'dart:async';

import 'package:flutter/material.dart';

import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:hydrated_bloc/hydrated_bloc.dart';

void main() async {
  // https://github.com/flutter/flutter/pull/38464
  // Changes in Flutter v1.9.4 require you to call WidgetsFlutterBinding.ensureInitialized()
  // before using any plugins if the code is executed before runApp.
  // As a result, you will need the following line if you're using Flutter >=1.9.4.
  WidgetsFlutterBinding.ensureInitialized();
  HydratedBloc.storage = await HydratedStorage.build();
  runApp(App());
}

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (_) => BrightnessCubit(),
      child: BlocBuilder<BrightnessCubit, Brightness>(
        builder: (context, brightness) {
          return MaterialApp(
            theme: ThemeData(brightness: brightness),
            home: BlocProvider<CounterBloc>(
              create: (_) => CounterBloc(),
              child: CounterPage(),
            ),
          );
        },
      ),
    );
  }
}

class CounterPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final textTheme = Theme.of(context).textTheme;
    return Scaffold(
      appBar: AppBar(title: const Text('Counter')),
      body: BlocBuilder<CounterBloc, int>(
        builder: (BuildContext context, int state) {
          return Center(
            child: Text('$state', style: textTheme.headline2),
          );
        },
      ),
      floatingActionButton: Column(
        crossAxisAlignment: CrossAxisAlignment.end,
        mainAxisAlignment: MainAxisAlignment.end,
        children: <Widget>[
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 5.0),
            child: FloatingActionButton(
              child: const Icon(Icons.brightness_6),
              onPressed: () {
                context.bloc<BrightnessCubit>().toggleBrightness();
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 5.0),
            child: FloatingActionButton(
              child: const Icon(Icons.add),
              onPressed: () {
                context.bloc<CounterBloc>().add(CounterEvent.increment);
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 5.0),
            child: FloatingActionButton(
              child: const Icon(Icons.remove),
              onPressed: () {
                context.bloc<CounterBloc>().add(CounterEvent.decrement);
              },
            ),
          ),
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 5.0),
            child: FloatingActionButton(
              child: const Icon(Icons.delete_forever),
              onPressed: () async {
                final counterBloc = context.bloc<CounterBloc>();
                await counterBloc.clear();
                counterBloc.add(CounterEvent.reset);
              },
            ),
          ),
        ],
      ),
    );
  }
}

enum CounterEvent { increment, decrement, reset }

class CounterBloc extends Bloc<CounterEvent, int> with HydratedMixin {
  CounterBloc() : super(0) {
    hydrate();
  }

  @override
  Stream<int> mapEventToState(CounterEvent event) async* {
    switch (event) {
      case CounterEvent.decrement:
        yield state - 1;
        break;
      case CounterEvent.increment:
        yield state + 1;
        break;
      case CounterEvent.reset:
        yield 0;
        break;
    }
  }

  @override
  int fromJson(Map<String, dynamic> json) => json['value'] as int;

  @override
  Map<String, int> toJson(int state) => {'value': state};
}

class BrightnessCubit extends HydratedCubit<Brightness> {
  BrightnessCubit() : super(Brightness.light);

  void toggleBrightness() {
    emit(state == Brightness.light ? Brightness.dark : Brightness.light);
  }

  @override
  Brightness fromJson(Map<String, dynamic> json) {
    return Brightness.values[json['brightness'] as int];
  }

  @override
  Map<String, dynamic> toJson(Brightness state) {
    return <String, int>{'brightness': state.index};
  }
}