如何在FutureBuilder小部件的构建器方法中获得未来的结果？

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'FutureBuilder示例',
      home: Scaffold(
        appBar: AppBar(
          title: Text('FutureBuilder示例'),
        ),
        body: FutureBuilder<String>(
          future: fetchData(), // 异步操作返回的Future对象
          builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              // 正在等待结果返回时显示的小部件
              return CircularProgressIndicator();
            } else if (snapshot.hasError) {
              // 如果出现错误，则显示错误信息
              return Text('Error: ${snapshot.error}');
            } else {
              // 成功返回数据时显示的小部件
              return Text('Data: ${snapshot.data}');
            }
          },
        ),
      ),
    );
  }
}

void main() {
  runApp(MyApp());
}