Flutter Firebase Auth异常未被catch捕获

发布于04月17日

当使用错误的凭据登录时，会像预期的那样抛出Exception.然而，catch block未能赶上Exception，导致坠机.

发生异常.FirebaseAuthExcept ([firebase_auth/invalid-credential]提供的auth凭据是不正确、格式错误或已过期.)

void signInWithEmail(String email, String password) async {
  state = state.copyWith(isLoading: true);
  try {
    UserCredential result = await _auth.signInWithEmailAndPassword(email: email.trim(), password: password.trim());
    state = state.copyWith(user: await _createMyUserFromFirebaseUser(result.user!), isLoading: false);
  } on FirebaseAuthException catch (e) {
    state = state.copyWith(isLoading: false, error: e.toString());
  } on PlatformException catch (_) {} catch (_) {}
}

我发现其他提到了这个问题，但从未找到过解决方案.正如您所看到的，我try 指定要捕获的异常，但不知何故，它从未被捕获.

推荐答案

我创建了一个例子来展示might会发生什么:

typedef State = ({String userName, bool isLoading, String error});

State state = (userName: 'not set', isLoading: true, error: 'nothing');

void signInWithEmail({
  required String email,
  required String password,
  Function? errorCallback,
}) async {
  if (errorCallback == null) {
    final userName = await Future.delayed(Duration.zero, () => 'Nick2001');
    state = (userName: userName, isLoading: false, error: 'nothing');
  } else {
    throw errorCallback();
  }
}

void main() async {
  try {
    signInWithEmail(
      email: 'a@b.com',
      password: '1234',
      errorCallback: () => 'User not registered.',
    );
    print(state);
  } catch (e) {
    print('Caught error in main:');
    print('  $e');
  }
}

尽管catch块已设置为捕获每个可能的异常，但该程序仍会生成以下控制台输出.

$ dart main.dart
State: (error: nothing, isLoading: true, userName: not set)
Unhandled exception:
Exception: User not registered.
#0      signInWithEmail (file:///work/main.dart:14:5)
#1      main (file:///work/main.dart:20:5)
#2      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:297:19)
#3      _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)

现在我们将函数signInWithEmail的签名更改为返回Future<void>并在main中等待该函数:

Future<void> signInWithEmail({
  required String email,
  required String password,
  Function? errorCallback,
}) async {
  if (errorCallback == null) {
    final userName = await Future.delayed(Duration.zero, () => 'Nick2001');
    state = (userName: userName, isLoading: false, error: 'nothing');
  } else {
    throw errorCallback();
  }
}

void main() async {
  try {
    await signInWithEmail(
      email: 'a@b.com',
      password: '1234',
      errorCallback: () => Exception('User not registered.'),
    );
    print('State: $state');
  } catch (e) {
    print('Caught error in main:');
    print('  $e');
  }
}

运行此程序会产生预期的输出:

Caught error in main:
  Exception: User not registered.

有关详细解释，请参阅Handling errors in void Dart function marked async. 简而言之:标记为"spec"的函数中引发的错误是future 错误.如果该函数在try-catch块中等待为not，那么在同步执行的try-catch块完成后将抛出future 错误，因此不会被捕获.