Flutter中无法捕获FirebaseAuthException的问题及解决

问题场景 #

尝试通过try-catch捕获Firebase登录时的FirebaseAuthException，但始终失败，控制台抛出未处理的异常。

错误代码 #

TextButton(
  onPressed: () async {
    try {
      final email = _email.text;
      final password = _password.text;

      final userCredential =
          FirebaseAuth.instance.signInWithEmailAndPassword(
        email: email,
        password: password,
      );
      print(userCredential);
    } on FirebaseAuthException catch (e) {
      if (e.code == 'user-not-found') {
        print(e.message);
      }
    }
  },
  child: Text("Login"),
),

控制台输出 #

I/FirebaseAuth( 2241): Logging in as asdasdhas@gmail.com with empty reCAPTCHA token
E/RecaptchaCallWrapper( 2241): Initial task failed for action RecaptchaAction(action=custom_signInWithPassword)with exception - There is no user record corresponding to this identifier. The user may have been deleted.
E/flutter ( 2241): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: [firebase_auth/user-not-found] There is no user record corresponding to this identifier. The user may have been deleted.

问题原因 #

signInWithEmailAndPassword是异步方法，调用时未添加await关键字，导致代码直接返回Future<UserCredential>对象，不会等待异步操作完成并捕获其抛出的异常，异常最终以未处理的Future异常形式抛出。

修复方案 #

在调用signInWithEmailAndPassword时添加await关键字，确保异步操作完成后再执行后续代码，此时异常会被正确捕获到try-catch块中：

TextButton(
  onPressed: () async {
    try {
      final email = _email.text;
      final password = _password.text;

      final userCredential = await FirebaseAuth.instance.signInWithEmailAndPassword(
        email: email,
        password: password,
      );
      print(userCredential);
    } on FirebaseAuthException catch (e) {
      if (e.code == 'user-not-found') {
        print(e.message);
      }
    }
  },
  child: Text("Login"),
),

内容的提问来源于stack exchange，提问作者Alin Ahmet Tekin