flutter官网MyApp例子报错

Question

官网示例：

复制过来的代码：

import 'package:flutter/material.dart';
import 'package:english_words/english_words.dart';

// import 'package:flutter/foundation.dart';
// import 'dart:developer';

// void main() {
//   runApp(const MyApp());
// }
void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    print('测试1111 ${MyApp}');
    return MaterialApp(
      title: '33333 Demo',
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Welcome to myapp11'),
        ),
        body: const Center(
          child: Text('Hello World'),
        ),
      ),
    );
  }
}

如果和官网一样不写const MyApp({Key? key}) : super(key: key); 就会报错
我把这行代码加上就不会报错，而且不太理解为什么MyApp类里又const一个MyApp变量

Answer 1

这是构造方法，就是别的语言中的 init