flutter实现上拉加载下拉刷新

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。以下是一个简单的示例代码：

import 'package:flutter/material.dart';
 
class RefreshLoadList extends StatefulWidget {
  @override
  _RefreshLoadListState createState() => _RefreshLoadListState();
}
 
class _RefreshLoadListState extends State<RefreshLoadList> {
  final ScrollController _scrollController = ScrollController();
  List<String> _items = List.generate(30, (index) => "Item ${index + 1}");
  bool _isLoading = false;
 
  @override
  void initState() {
    super.initState();
    _scrollController.addListener(_scrollListener);
  }
 
  @override
  void dispose() {
    _scrollController.dispose();
    super.dispose();
  }
 
  void _scrollListener() {
    if (_isLoading) return;
    if (_scrollController.position.pixels == _scrollController.position.maxScrollExtent) {
      setState(() {
        _isLoading = true;
      });
      // 模拟加载更多数据
      Future.delayed(Duration(seconds: 2), () {
        setState(() {
          _items.addAll(List.generate(10, (index) => "Item ${_items.length + 1}"));
          _isLoading = false;
        });
      });
    }
  }
 
  Future<void> _refreshList() async {
    await Future.delayed(Duration(seconds: 2));
    setState(() {
      _items = List.generate(30, (index) => "Item ${index + 1}");
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return RefreshIndicator(
      onRefresh: _refreshList,
      child: ListView.builder(
        controller: _scrollController,
        itemCount: _items.length,
        itemBuilder: (context, index) {
          return _isLoading && index == _items.length - 1
              ? Center(child: CircularProgressIndicator())
              : ListTile(title: Text(_items[index]));
        },
      ),
    );
  }
}
 
void main() {
  runApp(MaterialApp(home: RefreshLoadList()));
}

在这个示例中，RefreshLoadList是一个有状态的小部件，它包含一个ListView和一个ScrollController。_scrollListener方法监听滚动事件，当用户到达列表底部时，它会检查是否正在加载，如果没有，它会模拟加载更多数据。_refreshList方法处理下拉刷新操作，它会更新列表中的项目。这个例子使用了Future.delayed来模拟异步数据加载，实际应用中应该替换为实际的数据加载逻辑。