无法无条件调用该函数，因为尝试从 firebase Auth 获取当前用户信息时可能会显示“null”错误

Question

创建新用户后尝试获取当前用户信息，但在尝试调用“.currentUser()”方法时出现此错误“无法无条件调用该函数，因为它可以为‘null’”如何解决此问题？

这是尝试调用“final user=await _auth.currentUser();”时发生错误的代码

enter code here
import 'package:flutter/material.dart';
import 'package:firebase_auth/firebase_auth.dart';

class RegistrationScreen extends StatefulWidget {
@override
_RegistrationScreenState createState() => _RegistrationScreenState();
}

class _RegistrationScreenState extends State<RegistrationScreen> {
final  _auth =FirebaseAuth.instance;

late String eMail;
late String password;
@override
Widget build(BuildContext context) {
return Scaffold(
  backgroundColor: Colors.white,
  body: Padding(
    padding: EdgeInsets.symmetric(horizontal: 24.0),
    child: Column(
      mainAxisAlignment: MainAxisAlignment.center,
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: <Widget>[
        Container(
          height: 200.0,
          child: Image.asset('images/logo.png'),
        ),
        SizedBox(
          height: 48.0,
        ),
        TextField(
          onChanged: (value) {
            //Do something with the user input.
            eMail=value;
          },
        ),
        SizedBox(
          height: 8.0,
        ),

        TextField(
          onChanged: (value) {
            //Do something with the user input.
            password=value;
          },

        ),
        SizedBox(
          height: 24.0,
        ),
        Padding(
          padding: EdgeInsets.symmetric(vertical: 16.0),
          child: Material(
            color: Colors.blueAccent,
            borderRadius: BorderRadius.all(Radius.circular(30.0)),
            elevation: 5.0,
            child: MaterialButton(
              onPressed: () async {
                try{
                  final _newUser= await _auth.createUserWithEmailAndPassword(email: eMail, password: password);
                  if(_newUser!=null)
                    {
                       final  user=await _auth.currentUser();



                    }
                }
                catch(e)
                {
                  print(e);
                }

              },
              minWidth: 200.0,
              height: 42.0,
              child: Text(
                'Register',
                style: TextStyle(color: Colors.white),
              ),
            ),
          ),
        ),
      ],
    ),
  ),
);
}
}

Answer 1

问题是我正在调用“final user =_auth.currentUser()”函数，该函数已更改为“final user =_auth.currentUser” currentUser 是一个吸气剂，也不需要等待关键字并从中获取电子邮件、uid 等我们应该检查的用户 如果用户为空，则访问电子邮件和 uid 等。

enter code here
final _newUser= await _auth.createUserWithEmailAndPassword(email: eMail, password: password);
 if(_newUser!=null)
       {

         final  user =_auth.currentUser;

             if(user!=null)
                   {
                     final email = user.email;
                      print(email);
                    }
        }

Answer 2

正如错误所示，您应该添加一个空检查，如下所示：

filan user = await _auth!.currentUser();

因为

_auth

可以为空。您也可以使用此代码：

filan user = await _auth?.currentUser() ?? User(); // the name of user class