如何让RefreshIndicator消失？

import 'package:flutter/material.dart';

class MyPage extends StatefulWidget {
  @override
  _MyPageState createState() => _MyPageState();
}

class _MyPageState extends State<MyPage> {
  bool _isRefreshing = false;

  Future<void> _refreshData() async {
    // 模拟刷新数据的过程
    await Future.delayed(Duration(seconds: 2));
    setState(() {
      _isRefreshing = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('My Page'),
      ),
      body: RefreshIndicator(
        onRefresh: _refreshData,
        child: ListView(
          children: <Widget>[
            // 列表项
          ],
        ),
      ),
    );
  }
}