Flutter-Listview实现上拉加载和下拉刷新

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:video_player/video_player.dart';

void main() {
  runApp(new MaterialApp(
    title: 'Container demo',
    home: new MyListview(),
  ));
}

class MyListview extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return _ListViewState();
  }
}

class _ListViewState extends State<MyListview> {
  //lv数据集合
  List<String> _list = List.generate(20, (i) => '原始数据${i + 1}');

  ScrollController _scrollController;

  //是否正在加载,防止多次请求加载下一页
  bool isLoadingMore = false;

  @override
  void initState() {
    super.initState();
    //初始化ScrollController
    _scrollController = ScrollController();
    //监听lv是否滚动到底部
    _scrollController.addListener(() {
      if (_scrollController.position.pixels >=
          _scrollController.position.maxScrollExtent) {
        //滚动到了底部
        print('滚动到底部了');
        _loadMore();
      }
    });
  }

  @override
  void dispose() {
    super.dispose();
    //移除监听
    _scrollController.dispose();
  }

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Scaffold(
      appBar: AppBar(
        title: Text("列表的下拉刷新和上拉加载"),
      ),
      body: Container(
        child: RefreshIndicator(
          child: ListView.builder(
//            itemBuilder: (context, index) => ListTile(
            itemBuilder: (context, index) {
              if (index < _list.length) {
                return ListTile(
                  title: Text(_list[index]),
                );
              } else {
                //最后一页
                return _buildLoadMoreItem();
              }
            },
            itemCount: _list.length + 1,
            controller: _scrollController,
          ),
          onRefresh: _handleRefresh,
        ),
      ),
    );
  }

//下拉刷新的方法
  Future<Null> _handleRefresh() async {
    //模拟数据的延迟加载
    await Future.delayed(Duration(seconds: 2), () {
      setState(() {
        //在列表开头添加几条数据
        List<String> _refreshData = List.generate(5, (i) => '下拉刷新数据${i + 1}');
        _list.insertAll(0, _refreshData);
      });
    });
  }

//上拉加载
  Future<Null> _loadMore() async {
//模拟延迟加载
    if (!isLoadingMore) {
      setState(() {
        isLoadingMore = true;
      });
      await Future.delayed(Duration(seconds: 2), () {
        setState(() {
          isLoadingMore = false;
          List<String> _loadMoreData =
              List.generate(5, (i) => '上拉加载数据${i + i}');
          _list.addAll(_loadMoreData);
        });
      });
    }
  }

  //加载更多的布局
  Widget _buildLoadMoreItem() {
    return Center(
        child: Padding(
      padding: EdgeInsets.all(10.0),
      child: Text("加载中..."),
    ));
  }
}