如何在FutureBuilder (builder:)中引用方法中的变量？

FutureBuilder(
  future: fetchData(),
  builder: (BuildContext context, AsyncSnapshot snapshot) {
    if (snapshot.connectionState == ConnectionState.waiting) {
      return CircularProgressIndicator();
    } else if (snapshot.hasError) {
      return Text('Error: ${snapshot.error}');
    } else {
      var data = snapshot.data; // 获取异步请求返回的数据
      return Text('Data: $data');
    }
  },
)

Widget _buildWidget() {
  var data; // 定义一个变量用于存储异步请求返回的数据

  return FutureBuilder(
    future: fetchData(),
    builder: (BuildContext context, AsyncSnapshot snapshot) {
      if (snapshot.connectionState == ConnectionState.waiting) {
        return CircularProgressIndicator();
      } else if (snapshot.hasError) {
        return Text('Error: ${snapshot.error}');
      } else {
        data = snapshot.data; // 将异步请求返回的数据赋值给变量data
        return Text('Data: $data');
      }
    },
  );
}