NoSuchMethodError 被抛出构建 Home(dirty, state: HomeState#0a71e): The getter 'displayName' was called on null

Question

我正在尝试从 FirebaseAuth 中获取 UserEmail 和 UserName，我得到的结果 100% 正确，但它会抛出错误->“getter 'displayName' was called on null。” "接收者：null" "尝试调用：displayName"

class HomeState extends State<Home> {
    String accountStatus = '******';
    FirebaseUser mCurrentUser;
    FirebaseAuth _auth;
    @override
   void initState() {
      super.initState();
      _auth = FirebaseAuth.instance;
      _getCurrentUser();
    }
   _getCurrentUser () async {
      mCurrentUser = await _auth.currentUser();
      print('Hello ' + mCurrentUser.displayName.toString());
      print('Email ' + mCurrentUser.email.toString());
      setState(() {
        mCurrentUser != null ? accountStatus = 'Signed In' : 'Not Signed In';
    });
}

这是一个错误

I/flutter (11647): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (11647): The following NoSuchMethodError was thrown building Home(dirty, state: HomeState#0a71e):
I/flutter (11647): The getter 'displayName' was called on null.
I/flutter (11647): Receiver: null
I/flutter (11647): Tried calling: displayName
I/flutter (11647): 
I/flutter (11647): When the exception was thrown, this was the stack:
I/flutter (11647): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
I/flutter (11647): #1      HomeState.build (package:shopping_zone/UI/Home.dart:58:61)
I/flutter (11647): #2      StatefulElement.build (package:flutter/src/widgets/framework.dart:4012:27)
.
.
.
.
I/flutter (11647): Hello Lina
I/flutter (11647): Email lina19@gmail.com

Answer 1

如果没有用户连接，mCurrentUser 将是 null，当您打印 mCurrentUser.displayName.toString() 时会出现该错误。

您应该在打印之前测试用户是否为空：

if (mCurrentUser != null)
  print('Hello ' + mCurrentUser.displayName.toString());
  print('Email ' + mCurrentUser.email.toString());
}