bloc navigation using builder

flutter_navigation_with_bloc.dart

void main() {
  runApp(
    BlocProvider(
      create: (context) => MyBloc(),
      child: MyApp(),
    ),
  );
}

@immutable
abstract class MyEvent {}

class EventA extends MyEvent {}

class EventB extends MyEvent {}

@immutable
abstract class MyState {}

class StateA extends MyState {}

class StateB extends MyState {}

class MyBloc extends Bloc<MyEvent, MyState> {
  MyBloc() : super(StateA()) {
    on<EventA>((event, emit) => emit(StateA()));
    on<EventB>((event, emit) => emit(StateB()));
  }
}

### methode 1: use blocBuilder on materialApp and emit the state you want StateA for Page A

Widget build(BuildContext context) {
    return MaterialApp(
      home: BlocBuilder<MyBloc, MyState>(
        builder: (_, state) => state is StateA ? PageA() : PageB(),
      ),
    );
  }

### methode 2 : we can also use the BlocListener to manage it 
 @override
  Widget build(BuildContext context) {
    return MaterialApp(
      routes: {
        '/': (context) => PageA(),
        '/pageB': (context) => PageB(),
      },
      initialRoute: '/',
    );
  }
}

return BlocListener<MyBloc, MyState>(
      listener: (context, state) {
        if (state is StateB) {
          Navigator.of(context).pushNamed('/pageB');
        }
      },