类型“Future<void>”不是类型“Widget”的子类型

import 'package:flutter/material.dart';

class MyWidget extends StatelessWidget {
  Future<String> fetchData() async {
    // 模拟异步操作
    await Future.delayed(Duration(seconds: 2));
    return 'Hello World';
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder<String>(
      future: fetchData(),
      builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
        if (snapshot.connectionState == ConnectionState.waiting) {
          // 异步操作正在进行中，显示加载指示器
          return CircularProgressIndicator();
        } else if (snapshot.hasError) {
          // 异步操作发生错误，显示错误信息
          return Text('Error: ${snapshot.error}');
        } else {
          // 异步操作完成，根据结果构建界面
          return Text('Data: ${snapshot.data}');
        }
      },
    );
  }
}