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[英]Flutter StreamProvider returns null object eventhough stream is returning objects
[英]Flutter: StreamProvider<FirebaseUser> with onAuthStateChanged always returns null as a first value
我正在尝试根据身份验证状态创建一个简单的导航到 Firebase,但由于某种原因Provider.of<FirebaseUser>(context)
总是返回 null 作为小部件构建方法中的第一个值。 所以我的应用程序总是导航到身份验证屏幕,然后从 Firebase 获取真实的用户状态。 我在这里缺少什么?
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
.then((_) => runApp(App()));
}
class App extends StatelessWidget {
@override
Widget build(BuildContext context) {
return StreamProvider<FirebaseUser>.value(
//value of user always corresponds to the right auth status
value: FirebaseAuth.instance.onAuthStateChanged.map((FirebaseUser user) {
AuthService.instance.user = user;
return user;
}),
child: MaterialApp(
title: 'Title',
theme: lightTheme,
home: LandingScreen(),
),
);
}
}
class LandingScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
//Even though the user is logged in it returns null for the first build() call
final user = Provider.of<FirebaseUser>(context);
return AnimatedSwitcher(
duration: const Duration(milliseconds: 3000),
transitionBuilder: ...,
child: user != null ? const MainScreen() : const AuthScreen(),
);
}
}
我正在尝试根据对Firebase的身份验证状态创建一个简单的导航,但是由于某种原因, Provider.of<FirebaseUser>(context)
始终在小部件构建方法中始终将null作为第一个值返回。 因此,我的应用程序始终导航到“身份验证”屏幕,然后从Firebase获取真实的用户状态。 我在这里想念什么?
Future<void> main() async {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
.then((_) => runApp(App()));
}
class App extends StatelessWidget {
@override
Widget build(BuildContext context) {
return StreamProvider<FirebaseUser>.value(
//value of user always corresponds to the right auth status
value: FirebaseAuth.instance.onAuthStateChanged.map((FirebaseUser user) {
AuthService.instance.user = user;
return user;
}),
child: MaterialApp(
title: 'Title',
theme: lightTheme,
home: LandingScreen(),
),
);
}
}
class LandingScreen extends StatelessWidget {
@override
Widget build(BuildContext context) {
//Even though the user is logged in it returns null for the first build() call
final user = Provider.of<FirebaseUser>(context);
return AnimatedSwitcher(
duration: const Duration(milliseconds: 3000),
transitionBuilder: ...,
child: user != null ? const MainScreen() : const AuthScreen(),
);
}
}
您可以订阅 FirebaseAuth authStateChanges()
流以监听用户当前的身份验证状态。
FirebaseAuth.instance
.authStateChanges()
.listen((User? user) {
if (user == null) {
print('User is currently signed out!');
} else {
print('User is signed in!');
}
}
);
但是检查您提供的代码,正在获取final user = Provider.of<FirebaseUser>(context);
上的身份验证状态final user = Provider.of<FirebaseUser>(context);
. 如果用户登录时未更新提供程序,则它将始终为空。 您可能希望改用FirebaseAuth.instance.currentUser()
。
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