无法在初始化程序中访问实例成员“userInfo”[重复]答案

【问题标题】：The instance member 'userInfo' can't be accessed in an initializer [duplicate]无法在初始化程序中访问实例成员“userInfo”[重复]
【发布时间】：2022-03-05 20:34:11
【问题描述】：

我想将 Paricipant 类的实例传递给标签栏。我试图让List迟到，但它没有显示开头的信息（我必须转到另一个页面并返回查看）。

class MainTabBar extends StatelessWidget {
  MainTabBar({Key? key, required this.userInfo}) : super(key: key);

  final ParticipantInfo userInfo;

  final List<ItemView> items = <ItemView>[
    ItemView(title: "User", icon: Icons.account_box, view: UserProfileTab(userInfo: userInfo)),
    ItemView(title: "Current State", icon: Icons.content_paste, view: CurrentStatesTab(roomNumber: userInfo.location,)),
    const ItemView(title: "All data", icon: Icons.table_rows_rounded, view: AllInfoTab()),

  ];

  @override
  Widget build(BuildContext context) {......

lib/main.dart:44:85: Error: Can't access 'this' in a field initializer to read 'userInfo'.
    ItemView(title: "User", icon: Icons.account_box, view: UserProfileTab(userInfo: userInfo)),
                                                                                    ^^^^^^^^
lib/main.dart:45:100: Error: Can't access 'this' in a field initializer to read 'userInfo'.
    ItemView(title: "Current State", icon: Icons.content_paste, view: CurrentStatesTab(roomNumber: userInfo.location,)),

【问题讨论】：

标签： flutter dart

【解决方案1】：

你不能像这样使用实例变量来初始化另一个实例变量。

class Product {
  final String name;
  final int price = name.length
  
  Product({required this.name});
}

相反，在构造函数中对其进行初始化：

class Product {
  final String name;
  final int price;
  
  Product({required this.name}): price = name.length;
}

【讨论】：