Flutter如何实现下拉刷新和上拉加载更多，内含福利

在Flutter中，你可以使用RefreshIndicator和ListView来实现下拉刷新，使用ScrollController来实现上拉加载更多。以下是一个简单的示例代码：

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}
 
class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}
 
class _HomePageState extends State<HomePage> {
  List<String> items = List.generate(20, (i) => "Item ${i + 1}");
  final ScrollController _scrollController = ScrollController();
 
  @override
  void initState() {
    super.initState();
    _scrollController.addListener(() {
      if (_scrollController.position.pixels == _scrollController.position.maxScrollExtent) {
        setState(() {
          items.addAll(List.generate(20, (i) => "Item ${i + 21}"));
        });
      }
    });
  }
 
  @override
  void dispose() {
    _scrollController.dispose();
    super.dispose();
  }
 
  Future<void> _refresh() async {
    await Future.delayed(Duration(seconds: 2));
    setState(() {
      items = List.generate(20, (i) => "Item ${i + 1}").toList();
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('下拉刷新和上拉加载'),
      ),
      body: RefreshIndicator(
        onRefresh: _refresh,
        child: ListView.builder(
          controller: _scrollController,
          itemCount: items.length,
          itemBuilder: (context, index) {
            return ListTile(
              title: Text(items[index]),
            );
          },
        ),
      ),
    );
  }
}

在这个示例中，RefreshIndicator包裹了ListView，它会在用户下拉时触发_refresh方法来刷新数据。ScrollController监听滚动事件，当列表滚动到底部时，会加载更多数据。这里使用了Future.delayed来模拟异步数据加载，实际应用中应替换为实际的数据加载逻辑。