Flutter笔记--下拉刷新与上拉加载更多

 下拉刷新与上拉加载更多在一般项目中很多地方都会用到，来看看Flutter中最简单的实践：

 1 下拉刷新(用变化数据来演示)

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

class PullToRefreshPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
   return _PullToRefreshPage();
  }
}


class _PullToRefreshPage extends State<PullToRefreshPage> {
  List<int> items = List.generate(16, (index) => index);
  ScrollController _scrollController = new ScrollController();
  bool isLoading = false;

  Future<Null> _handleRefresh() async {
    await Future.delayed(Duration(seconds:3),() {
      print('refresh');
      setState(() {
        items.clear();
        items = List.generate(30, (index) => index);
        return null;
      });
    });
  }


@override
  Widget build(BuildContext context) {
    return
      Scaffold(
      appBar: AppBar(title: Text("Refresh"),),
      body: new RefreshIndicator(
          child: ListView.builder(
          itemCount: items.length,
          itemBuilder: (context,index) {
            return ListTile(title: Text("Index$index"),);
          },
          ),
      onRefresh:_handleRefresh
      ),
    );

}

2 上拉加载更多

class _PullToRefreshPage extends State<PullToRefreshPage> {
  List<int> items = List.generate(16, (index) => index);
  ScrollController _scrollController = new ScrollController();
  bool isLoading = false;


 @override
  Widget build(BuildContext context) {
    return
       Scaffold(
          appBar: AppBar(
            title: Text("LoadMore"),
          ),
          body:  ListView.builder(
            itemCount: items.length + 1,
            itemBuilder: (context, index) {
              // return ListTile(
              //     title: Text("Index$index"));
              print('------>--index---$index');
              if(index == items.length) {
                // return _buildLoadText();
                return _buildProgressIndicator();
              } else {
                return ListTile(title:Text("Index$index"));
              }
            },
            controller: _scrollController,
          )
      );
}

 Widget _buildLoadText() {
    return Container(child: Padding(
      padding: const EdgeInsets.all(18.0),
      child:Center(
        child: Text("加载中....."),
      )
    ));
  }

  Widget _buildProgressIndicator() {
    return new Padding(
      padding:const EdgeInsets.all(8.0),
      child:new Center(
          child:new CircularProgressIndicator(),
      )
    );
  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    print('---_scrollController---->');
    _scrollController.addListener(() {
      print('---initState---->');
      if(_scrollController.position.pixels == _scrollController.position.maxScrollExtent) {
        print('loadMore');
        _getMoreData();
      }
      print('---_scrollController----End-->');
    });
  }

  Future _getMoreData() async {
    List<int> newEntries = await makeHttpRequest(items.length,items.length+10);
    setState(() {
      items.addAll(newEntries);
      isLoading = false;
    });
  }

  Future<List<int>> makeHttpRequest(int from,int to) async {
    return Future.delayed(Duration(seconds:2),() {
       return List.generate(to-from,(i) => i+from);
    });
  }

  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
    _scrollController.dispose();
  }


}