firebase - 在 Flutter 中使用 FirebaseAuth 检查用户的身份验证状态

Question

我知道存在这样的问题，但它充满了过时和不正确的答案。新款FlutterFire文档使用 Streams 来获取用户的状态，我很难尝试执行如此微不足道的任务，因为我对 Flutter 和 Dart 缺乏经验。这是过时问题的答案和引用。

答案:https://stackoverflow.com/a/50714618/14080391

引用:https://firebase.flutter.dev/docs/auth/usage#authentication-state

我期待与 StreamBuilder 一起得到答案，这是我迄今为止编写的代码:

@override
  Widget build(BuildContext context) {
    return StreamBuilder(
      builder: (BuildContext context, AsyncSnapshot<dynamic> snapshot) { 
        if(snapshot.hasData) {
          print("data exists");
          return snapshot.data ? First() : SignIn();
        }
        else {
          return SignIn();
        }
      },
      future: isUserLoggedIn(),
    );
  }

Stream<bool> isUserLoggedIn() {
    FirebaseAuth.instance
        .authStateChanges()
        .listen((User user) {
      if (user == null) {
        print('User is currently signed out!');
        // return false; ???
      } else {
        print('User is signed in!');
        // return true; ???
      }
    });
  }

编辑:

Firebase Auth enables you to subscribe in realtime to this state via a >Stream. Once called, the stream provides an immediate event of the user's >current authentication state, and then provides subsequent events whenever ?the authentication state changes.

FlutterFire Auth Doc

Answer 1

isUserLoggedIn()不返回任何类型的流。我建议只听实际 authStateChanges()溪流。

  Widget build(BuildContext context) {
    return StreamBuilder<User>(
      stream: FirebaseAuth.instance.authStateChanges(),
      builder: (BuildContext context, AsyncSnapshot<User> snapshot) { 
        if(snapshot.hasData) {
          print("data exists");
          return First();
        }
        else {
          return SignIn();
        }
      },
    );
  }