How to globally listen from a flutter bloc?

Question

I'm implementing notifications on my app.

I have a Cubit that will emit states when the app receives a new notification.

This is my main:

class MyApp extends StatelessWidget {

 @override
  Widget build(BuildContext context) {
    return MultiBlocProvider(
        providers: [
          ...
          BlocProvider<NotificationCubit>(
              create: (context) => sl<NotificationCubit>())
        ],
        child: MaterialApp(
          home: Splash(),
          onGenerateRoute: Routes.sailor.generator(),
          navigatorKey: Routes.sailor.navigatorKey,
        ));
  }
}

I'm using get_it for dependency injection.

I tried to add BlocBuilder<NotificationCubit, NotificationState> to my home screen and it works every time the user receives the notification.

My goal is to handle the notification globally. I tried to add a listener when I create the cubit, but this doesn't work:

BlocProvider<NotificationCubit>(
          create: (context) => sl<NotificationCubit>()..listen((state) {
              if (state is NotificationReceived){
                  print("Notificaton received");
              }
           }))

Dharman · Accepted Answer · 2021-02-22 19:33:21Z

2

I have heard that using get_it with bloc is not a good idea...

Especially in your case, where you are providing a bloc for the whole widget tree. Try to provide bloc without using get_it because you will have access to it in the whole app anyways.

Here there is an interesting video about it: https://youtu.be/THCkkQ-V1-8?t=6393

edited Feb 22, 2021 at 19:33

Dharman♦

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answered Feb 22, 2021 at 19:27

csk

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2 Comments

Matteo Antolini Over a year ago

I changed sl<NotificationCubit>() to NotificationCubit( messaging: FirebaseMessaging(), localNotifications: FlutterLocalNotificationsPlugin()), but the problem still persist. I use get_it only to initialize blocs. When I need to access to them I use context.read() / context.watch()...

dKen Over a year ago

+1 for that video, it totally changed everything for me. Very long at 3.5 hours, but that's a testament to how complicated the topic is. Every minute was very valuable. Thanks!

Matteo Antolini · Accepted Answer · 2022-10-14 15:58:25Z

To globally listen to a bloc you need to put it above MaterialApp

return MultiBlocProvider(
        providers: [
          ...
          BlocProvider<NotificationCubit>(
              create: (context) => NotificationCubit()),
        ],
        child: Builder(
            builder: (context) =>
                BlocListener<NotificationCubit, NotificationState>(
                  listener: (context, state) {
                    ...
                  },
                  child: MaterialApp(
                  ...
                  )
        )),
);

Remember to use Builder or create another stateless class after using BlocProvider

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