这是集团(简化):
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>();
}
这是集团提供者:
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;
}
}
但是,在LoginScreen中,我无法访问集团的loggedIn
主题。以下是从main打开LoginScreen的方法,并将bloc传递给它:
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
);
}
}
以下是我尝试在登录屏幕中访问它的方法:
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();
}
错误:
getter'loginIn'在null上调用。
那么为什么集团无效呢?我该如何解决?
在这一行中,BlocProvder期待一个集团。
home: BlocProvider<LoginBloc>(child: LoginScreen()),
你没有在这里通过你的集团。
传递方式如下:
home: BlocProvider<LoginBloc>(child: LoginScreen(),bloc: LoginBloc()),
BlocProvider<LoginBloc>
意味着你定义一个你要通过的集团类型。