未处理的异常：NoSuchMethodError：在 null 上调用了 getter 'isEmailVerified'

Question

I am getting the above mentioned error when logging in. This exception is raised even after I am ensuring that the isEmailVerified() is called only after checking whether the current user is null or not.

My authentication.dart file looks like below:

import 'dart:async';
import 'package:firebase_auth/firebase_auth.dart';

abstract class BaseAuth {
  Future<String> signIn(String email, String password);

  Future<String> signUp(String email, String password);

  Future<FirebaseUser> getCurrentUser();

  Future<void> sendEmailVerification();

  Future<void> signOut();

  Future<bool> isEmailVerified();
}
class Auth implements BaseAuth {
  final FirebaseAuth _firebaseAuth = FirebaseAuth.instance;

  Future<String> signIn(String email, String password) async {
    AuthResult result = await _firebaseAuth.signInWithEmailAndPassword(
        email: email, password: password);
    FirebaseUser user = result.user;
    return user.uid;
  }

  Future<String> signUp(String email, String password) async {
    AuthResult result = await _firebaseAuth.createUserWithEmailAndPassword(
        email: email, password: password);
    FirebaseUser user = result.user;
    sendEmailVerification();
    return user.uid;
  }

  Future<FirebaseUser> getCurrentUser() async {
    FirebaseUser user = await _firebaseAuth.currentUser();
    return user;
  }

  Future<void> signOut() async {
    return _firebaseAuth.signOut();
  }

  Future<void> sendEmailVerification() async {
    FirebaseUser user = await _firebaseAuth.currentUser();
    user.sendEmailVerification();
  }

  Future<bool> isEmailVerified() async {
    FirebaseUser user = await _firebaseAuth.currentUser();
    return user.isEmailVerified;
  }
}

And inside the LoginPage , I am checking like this:

if(auth.signIn(email, password)!=null)
      {
        if(auth.getCurrentUser()!=null)
          {
            if(auth.isEmailVerified() != null) {
              Toast.show("Login Successful!", context, duration: Toast.LENGTH_SHORT, gravity:  Toast.BOTTOM);
              Route route = MaterialPageRoute(builder: (context) => HomePage());
              Navigator.pushReplacement(context, route);
            }
          }
      }

I don't know how to resolve this. Any help is appreciated.

Answer 1

From your Auth class, your methods have future signatures.
You will have to await their results since it will be needed by the other conditions.

You can do:

if((await auth.signIn(email, password))!=null){
      if((await auth.getCurrentUser())!=null){
        if((await auth.isEmailVerified()) != null) {
          Toast.show("Login Successful!", context, duration: Toast.LENGTH_SHORT, gravity:  Toast.BOTTOM);
          Route route = MaterialPageRoute(builder: (context) => HomePage());
          Navigator.pushReplacement(context, route);
        }
      }
    }

But the snippet above must be placed in within an async method.