[Question] Bloc observer not working

[linxkaa]

Hi @felangel. I tried to implement of blocObserver after the migration.

this is what my blocObserver looks like.

// ignore_for_file: avoid_print

import 'package:bloc/bloc.dart';

class SimpleBlocObserver extends BlocObserver {
  @override
  void onCreate(BlocBase bloc) {
    super.onCreate(bloc);
    print('onCreate Bloc-- ${bloc.runtimeType}');
  }

  @override
  void onChange(BlocBase bloc, Change change) {
    super.onChange(bloc, change);
    print('onChange Bloc type-- ${bloc.runtimeType}');
    print('onChange Bloc CurrentState-- ${change.currentState}');
    print('onChange Bloc NextState-- ${change.nextState}');
  }

  @override
  void onError(BlocBase bloc, Object error, StackTrace stackTrace) {
    print('onError Bloc-- ${bloc.runtimeType}, $error');
    super.onError(bloc, error, stackTrace);
  }

  @override
  void onClose(BlocBase bloc) {
    super.onClose(bloc);
    print('onClose Bloc-- ${bloc.runtimeType}');
  }
}

and this is my main.dart file

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  BlocOverrides.runZoned(
    () {},
    blocObserver: SimpleBlocObserver(),
  );
  return  runApp(Env.dev));
}

and it didn't print anything. Previously i do this with Bloc.observer = SimpleBlocObserver() and my bloc will automatically printed in console. But now it doesn't.

if i put this this way:

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
    BlocOverrides.runZoned(
    () {
      cubitMain();
    },
    blocObserver: SimpleBlocObserver(),
  );
  return runApp(Env.dev);
}

with the cubitMain() codes like this:

void cubitMain() {
  print('----------CUBIT----------');
  final bloc = getIt<ShareImageBloc>();
  print(bloc.state); 
  cubit.close();
}

it will trigger only in the first time application is running, but not when the state is changed. While the previous version is whenever i create a bloc and trigger an event, the bloc observer should always be triggered.

Is there anything wrong with my code? Thank you in advance!

[felangel]

Hi @linxkaa 👋
Thanks for opening an issue!

Can you remove the WidgetsFlutterBinding.ensureInitialized and verify if that solves the problem? If you aren’t accessing the underlying platforms before runApp then you should remove it. If you need access to the underlying platforms then you should use https://pub.dev/packages/flutter_services_binding.

You can read more about this at flutter/flutter#94123.

Let me know if that helps and sorry for any inconvenience!

[linxkaa]

Hi @felangel thank you for responding!

I already changed to this

void main() {
  BlocOverrides.runZoned(
    () {},
    blocObserver: SimpleBlocObserver(),
  );
  return runTokocuanApp(TokocuanEnv.dev);
}

fyi the runApp i access in the code before isnt the actually runApp, i called other class like this

void runTokocuanApp(String env) async {
  WidgetsFlutterBinding.ensureInitialized();
  configureInjection(env);
  await SystemChrome.setPreferredOrientations(
    [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown],
  );
  return runApp(const TokocuanApp());
}

Things i tried: I already tried moving the BlocOverrides to runTokocuanApp and removes all the widgetsFlutterBinding, but nothing happen.

And i cant remove the WidgetsFlutterBinding.ensureInitialized() on the runTokocuanApp because it called this,

  await SystemChrome.setPreferredOrientations(
    [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown],
  );

if i remove it, it will throw this error

[felangel]

void main() {
  BlocOverrides.runZoned(
    () => runTokocuanApp(…),
    blocObserver: SimpleBlocObserver(),
  );
}

You need to move the code within the body of the zone.

[linxkaa]

Ohh i see! Thank you very much! Its working now!

[kashlo]

Ive tried the above solution, but observer still doesn't work, no logs are showing

[felangel]

Ive tried the above solution, but observer still doesn't work, no logs are showing

Can you provide a link to a minimal reproduction sample? Thanks!

[kashlo]

Future<void> main() async {
  await setUp();
  BlocOverrides.runZoned(
    () {
      return runApp(
        BlocProvider<AuthenticationBloc>(
          create: (_) => GetIt.instance<AuthenticationBloc>(),
          child: MyApp(),
        )
      );
    },
    blocObserver: SimpleBlocObserver(),
  );
}

Future<void> setUp() async {
  WidgetsFlutterBinding.ensureInitialized();

  GetIt.instance.registerSingleton<AuthenticationBloc>(AuthenticationBloc());
  GetIt.instance<AuthenticationBloc>().add(AppStarted());
}

[felangel]

WidgetsFlutterBinding.ensureInitialized();

This is because you're using WidgetsFlutterBinding.ensureInitialized();.

If you replace it with FlutterServicesBinding.ensureInitialized(); from package:flutter_services_binding it should resolve the issue.

You can see flutter/flutter#94123 for more info 👍

[kashlo]

added plugin, changed to FlutterServicesBinding.ensureInitialized();
still no logs from the observer :/

[felangel]

added plugin, changed to FlutterServicesBinding.ensureInitialized();
still no logs from the observer :/

Can you also move the setup into the runZoned body?

Future<void> main() async {
  await BlocOverrides.runZoned(
    () async {
      await setUp();
      return runApp(
        BlocProvider<AuthenticationBloc>(
          create: (_) => GetIt.instance<AuthenticationBloc>(),
          child: MyApp(),
        )
      );
    },
    blocObserver: SimpleBlocObserver(),
  );
}

[kashlo]

@felangel Now logs are visible, thanks a lot :)

[noor848]

hello i put it in this way and it doesnt work

void main() {

////FlutterServicesBinding.ensureInitialized();
BlocOverrides.runZoned(
() {
runApp(const MyApp());
},
blocObserver: MyBlocObserver(),
);

}

[felangel]

hello i put it in this way and it doesnt work

void main() {

////FlutterServicesBinding.ensureInitialized(); BlocOverrides.runZoned( () { runApp(const MyApp()); }, blocObserver: MyBlocObserver(), );

}

Can you share your full main.dart?

[noor848]

this is my main
/////////////

import 'package:bloc/bloc.dart';
import 'package:bma/counter.dart';
import 'package:bma/module/counter/cubit.dart';
import 'package:bma/module/counter/statecounter.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_services_binding/flutter_services_binding.dart';
import 'BMI_cal.dart';
import 'login_page.dart';
import 'module/square_rotate/square.dart';
import 'shared/blocobserver.dart';

void main() {

FlutterServicesBinding.ensureInitialized();
BlocOverrides.runZoned(
() {
runApp(const MyApp());
},
blocObserver: MyBlocObserver(),
);

}

class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);

@OverRide
Widget build(BuildContext context) {
return MaterialApp(

  debugShowCheckedModeBanner: false,
  home: Counter(),



);

}
}

[noor848]

i tried your both solution adding this FlutterServicesBinding.ensureInitialized(); and without and no result show

[felangel]

i tried your both solution adding this FlutterServicesBinding.ensureInitialized(); and without and no result show

Do you have a link to a minimal reproduction sample?

[noor848]

[noor848]

and this my simple work link
https://github.com/noor848/Flutter_project/tree/counter/lib/module/counter

[felangel]

and this my simple work link https://github.com/noor848/Flutter_project/tree/counter/lib/module/counter

I'm not able to reproduce the issue. You can refer to the official DartPad and see the BlocObserver logs in the console:

[noor848]

thank you it works actually i guess the problem was the ide is slow

[omarmorsi99]

hello this is my main with no log observer if you can help

Future main() async{
BlocOverrides.runZoned(
() => const MyApp(),
blocObserver: AppBlocObserver(),
);

WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);

}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@OverRide
Widget build(BuildContext context) {
return MultiBlocProvider(
providers: [
BlocProvider(create: (context) => AppCubit()..getUserData()..getPosts()..getUsers()),
],
child: BlocConsumer<AppCubit,AppStates>(
listener: (context, state) {},
builder: (context,state) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Register_Screen(),
);
}),
);
}
}

[felangel]

@omarmorsi99 you need to move your WidgetsFlutterBinding and Firebase calls within the runZoned callback like:

void main() {
  BlocOverrides.runZoned(
    () async {
      WidgetsFlutterBinding.ensureInitialized();
      await Firebase.initializeApp(options: DefaultFirebaseOptions.currentPlatform);
      runApp(const MyApp());
    },
    blocObserver: AppBlocObserver(),
  );
}

Hope that helps 👍

[Jashemaits]

Hello! onError is not getting called from blocObserver for blocs of nested page. but it is getting called on my tab bar but if i navigate to a different page and that page has a blocProvider that is not printing any error.