bloc does not get initialized when using generic bloc provider - dart

Question

Here is the bloc (simplified):
import 'package:autobleidas_flutter/bloc/bloc_base.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:rxdart/rxdart.dart';
class LoginBloc extends BlocBase {
final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;
final PublishSubject<bool> loggedIn = PublishSubject<bool>();
final PublishSubject<bool> loading = PublishSubject<bool>();
}
Here is the bloc provider:
class BlocProvider<T> extends InheritedWidget {
final T bloc;
BlocProvider({Key key, Widget child, this.bloc})
: super(key: key, child: child);
static T of<T extends BlocBase>(BuildContext context) {
final type = _typeOf<BlocProvider<T>>();
return (context.inheritFromWidgetOfExactType(type) as BlocProvider).bloc;
}
static Type _typeOf<T>() => T;
#override
bool updateShouldNotify(InheritedWidget oldWidget) {
return true;
}
}
However, in the LoginScreen I cannot access the loggedIn Subject of the bloc. Here is how LoginScreen is opened from main and the bloc is passed to it:
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData(
primarySwatch: Colors.blue,
),
localizationsDelegates: GlobalMaterialLocalizations.delegates,
supportedLocales: allTranslations.supportedLocales(),
home: BlocProvider<LoginBloc>(child: LoginScreen()), // <-------- HERE
);
}
}
Here is how I try to access it in the LoginScreen:
class _LoginScreenState extends State<LoginScreen> {
bool _isLoading = false;
#override
void didChangeDependencies() {
LoginBloc bloc = BlocProvider.of<LoginBloc>(context);
bloc.loggedIn.listen((isLoggedIn) => Navigator.of(context).push(
MaterialPageRoute(
builder: (BuildContext context) => RegistrationScreen())));
bloc.loading.listen((state) => setState(() => _isLoading = state));
super.didChangeDependencies();
}
#override
Widget build(BuildContext context) {
return Container();
}
the error:
The getter 'loggedIn' was called on null.
So why is the bloc null? How do I fix this?

Answer 1

In this line, BlocProvder expect a bloc.
home: BlocProvider<LoginBloc>(child: LoginScreen()),
You are not passing your bloc here.
Pass it like below:
home: BlocProvider<LoginBloc>(child: LoginScreen(),bloc: LoginBloc()),
BlocProvider<LoginBloc> means your defining a type of the bloc you are going to pass.