Emit was called after an event handler completed normally [Flutter] - flutter

Question

Exception is thrown on second call 'emit' inside 'firstEvent' case. I know why, but I dont know how to make it work. Problem exists when I use event.map.
_AssertionError
emit was called after an event handler completed normally.
This is usually due to an unawaited future in an event handler.
Please make sure to await all asynchronous operations with event handlers
and use emit.isDone after asynchronous operations before calling emit() to
ensure the event handler has not completed.
void main() {
runApp(const MyApp());
}
#freezed
class SampleEvent with _$SampleEvent {
const factory SampleEvent.firstEvent() = FirstEvent;
const factory SampleEvent.secondEvent() = SecondEvent;
}
#freezed
class SampleState with _$SampleState {
const factory SampleState.initialState() = InitialState;
const factory SampleState.firstState() = OneFirstState;
const factory SampleState.secondState() = SecondState;
}
class SampleBloc extends Bloc<SampleEvent, SampleState> {
SampleBloc() : super(const SampleState.initialState()) {
on<SampleEvent>(eventHandler);
}
FutureOr<void> eventHandler(
SampleEvent event,
Emitter<SampleState> emit,
) async {
event.map(
firstEvent: (value) async {
emit(const SampleState.firstState());
await Future.delayed(const Duration(seconds: 2));
// EXCEPTION!!! HERE:
emit(const SampleState.secondState());
},
secondEvent: (value) => null,
);
}
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: BlocProvider(create: (_) => SampleBloc(), child: const Home()),
);
}
}
class Home extends StatelessWidget {
const Home({super.key});
#override
Widget build(BuildContext context) {
return BlocConsumer<SampleBloc, SampleState>(
builder: (context1, state) {
return TextButton(
onPressed: () => context1.read<SampleBloc>().add(
const SampleEvent.firstEvent(),
),
child: const Text('Launch First Event'),
);
},
listener: (context, state) {},
);
}
}