提供者的状态管理

如果您打算在整个应用程序中使用FirebaseUser或“登录用户”，我建议您在应用程序的最高级别上添加提供程序。例

void main() {   runApp(MyApp());   }class MyApp extends StatelessWidget {  MyApp();  @override  Widget build(BuildContext context) {    return MultiProvider(      providers: [        StreamProvider<FirebaseUser>.value(          stream: FirebaseAuth.instance.onAuthStateChanged, // Provider here        ),      ],      child: MaterialApp(        title: 'My App',        debugShowCheckedModeBanner: false,        theme: ThemeData(          primaryColor: Colors.green,          primarySwatch: Colors.green,          accentColor: Colors.yellow,        ),        home: MainPage(),      ),    );  }}class MainPage extends StatefulWidget {  MainPage({Key key, this.storage}) : super(key: key);  final FirebaseStorage storage;  @override  _MainPageState createState() => _MainPageState();}class _MainPageState extends State<MainPage>    with SingleTickerProviderStateMixin {  @override  Widget build(BuildContext context) {    final user = Provider.of<FirebaseUser>(context); // gets the firebase user    bool loggedIn = user != null;    return loggedIn ? HomePage() : LoginPage(); // Will check if the user is logged in. And will change anywhere in the app if the user logs in  }}

参考资料

Fireship 185提供者

很棒的YouTube视频解释了代码