如何在FutureBuilder中正确使用setState？

class MyWidget extends StatefulWidget {
  @override
  _MyWidgetState createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  bool _dataLoaded = false;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('FutureBuilder with setState Example'),
      ),
      body: FutureBuilder<String>(
        future: _loadData(),
        builder: (context, AsyncSnapshot<String> snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            return Center(child: CircularProgressIndicator());
          } else if (snapshot.hasError) {
            return Center(child: Text('Error: ${snapshot.error}'));
          } else {
            // 当数据加载完成时，更新状态
            if (!snapshot.hasData) {
              setState(() {
                _dataLoaded = true;
              });
            }
            return Center(child: Text('Data: ${snapshot.data ?? ''}'));
          }
        },
      ),
    );
  }

  Future<String> _loadData() async {
    // 模拟异步数据加载
    await Future.delayed(Duration(seconds: 2));
    return 'Hello, Flutter!';
  }
}