Firebase身份验证！即使我输入了一个未注册的用户，我也可以转到主页

Question

我已经成功地将firebase添加到我的flutter2.0项目中。我还启用了身份验证。我还可以注册一个新用户。但是，在身份验证后转到主页的逻辑不起作用。即使我输入了错误的用户，我也可以登录。我想如果我输入正确的用户，然后我应该导航到主页，但如果用户没有注册它应该不能导航到下一页。ie..the身份验证的基本用法。但它不会发生在这里。即使我输入了错误的用户，我也能够导航到下一个位置。

Future signInWithEmailAndPassword(String email, String password) async {
    try {
  UserCredential userCredential = await FirebaseAuth.instance.signInWithEmailAndPassword(
    email:email,
    password:password,
  );
  
} on FirebaseAuthException catch (e) {
  if (e.code == 'user-not-found') {
    print('No user found for that email.');
  } else if (e.code == 'wrong-password') {
    print('Wrong password provided for that user.');
  }
}
  }

  Future newAccount(String email, String password) async {
    try {
      UserCredential userCredential = await FirebaseAuth.instance
          .createUserWithEmailAndPassword(email: email, password: password);
    } on FirebaseAuthException catch (e) {
      if (e.code == 'weak-password') {
        print('The password provided is too weak.');
      } else if (e.code == 'email-already-in-use') {
        print('The account already exists for that email.');
      }
    } catch (e) {
      print(e.toString());
    }
  }
}

//this is how I can this function and try to navigate to next page.
void logMeIn() {
    if (formKey.currentState!.validate()) {
      authMethods
          .signInWithEmailAndPassword(usernameTextEditingContoller.text,
              passwordTextEditingContoller.text)
          .then((value) {
            print('value is: ');
        print(value);
        Navigator.of(context)
            .pushReplacement(MaterialPageRoute(builder: (context) {
          return Home();
        }));
      });
    }
  }**strong text**

Answer 1

signInWithEmailAndPassword返回一个UserCredential对象。

在您的逻辑中，您正在使用.then((value) {...etc})

此value是signInWithEmailAndPassword的结果。

尝试将您的逻辑更改为：

authMethods
          .signInWithEmailAndPassword(usernameTextEditingContoller.text,
              passwordTextEditingContoller.text)
          .then((value) {
            print('value is: ');
        print(value);
        if(value.user ==null) return "Error in authentication"; // this will prevent your function form going further down the navigation if the usercredential doesn't have a valid user.
        Navigator.of(context)
            .pushReplacement(MaterialPageRoute(builder: (context) {
          return Home();