错误：在此 MyApp 小部件上方找不到正确的 Provider<SignInProvider>

Question

我正在尝试在 MaterialApp 中将 StreamProvider 与 MultiProvider 一起使用

当我尝试访问提供程序时，我收到以下错误：

错误：在此 MyApp 小部件上方找不到正确的提供程序

main.dart

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    final provider = Provider.of<SignInProvider>(context, listen: false);
    return MultiProvider(
      providers: [
        StreamProvider<UserModel>.value(value: provider.authStateChange())
      ],
      child: MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primaryColor: primaryColor,
          accentColor: secondaryColor,
          textTheme: customTextTheme
        ),
        home: AuthHandler()
      ),
    );
  }
}

class AuthHandler extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    UserModel _userModel = Provider.of<UserModel>(context);
    return (_userModel != null) ? HomeScreen() : LoginScreen();
  }
}

user_model.dart

class UserModel {
  String uid;
  String displayName;
  String photoURL;
  String email;

  UserModel({ this.uid, this.displayName, this.photoURL, this.email, });
}

signin_provider.dart

Stream<UserModel> authStateChange() {
    return firebaseAuth.authStateChanges().map((User user) => (user != null) ? UserModel(uid: user.uid) : null);
  }

Answer 1

转到 main.dart 并添加您的Provider：

---

例子：

void main() => runApp(MyApp());

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

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider<ThemeBloc>(
      create: (_) => ThemeBloc(),
      child: Consumer<ThemeBloc>(
        builder: (_, mode, child) {
          return MultiProvider(
            providers: [
              ChangeNotifierProvider<SignInBloc>(
                create: (context) => SignInBloc(),
              ),
              ChangeNotifierProvider<NewsDataBloc>(
                create: (context) => NewsDataBloc(),
              ),
              ChangeNotifierProvider<PopularDataBloc>(
                create: (context) => PopularDataBloc(),
              ),
           
          
            ],
            child: MaterialApp(
           
                home: MyHomePage()),
          );
        },
      ),
    );
  }
}

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

  @override
  Widget build(BuildContext context) {
  
      return WelcomePage();
   
  }
}