Flutter Bloc Counter Example

main.dart

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

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

abstract class CounterEvent {}

class Increment extends CounterEvent {}

class CounterBloc extends Bloc<CounterEvent, int> {
  CounterBloc() : super(0) {
    on<Increment>((event, emit) => emit(state + 1));
  }
}

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: BlocProvider(
        create: (_) => CounterBloc(),
        child: CounterPage(),
      ),
    );
  }
}

class CounterPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Counter')),
      body: Center(
        child: BlocBuilder<CounterBloc, int>(
          builder: (context, count) {
            return Text('$count', style: Theme.of(context).textTheme.headline1);
          },
        ),
      ),
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.add),
        onPressed: () => context.read<CounterBloc>().add(Increment()),
      ),
    );
  }
}