【flutter】下拉刷新，上滑加载

1、

ScrollController _scrollController = ScrollController(); //listview的控制器
  int _page = 1; //加载的页数
  bool isLoading = false; //是否正在加载数据


  @override
  void initState() {
    // TODO: implement initState
    super.initState();
   //监听下滑到ListView底部
    _scrollController.addListener(() {
      if (_scrollController.position.pixels ==
          _scrollController.position.maxScrollExtent) {
        print('滑动到了最底部');
        _getMore();
      }
    });
  }
  @override
  void dispose() {
    // TODO: implement dispose
    super.dispose();
    _scrollController.dispose();//销毁监听
  }

2、ListView的设置
ListView方式：

RefreshIndicator(
	 child: ListView(
	      controller: _scrollController, children: _getBody()),
	  onRefresh: _onRefresh
)

_getBody()方法中,最后加上加载判断

if(isLoading){//加载。。。样式
      list.add(_getMoreWidget());
    }

ListView.builder方式：

_onRefresh,
        child: ListView.builder(
          itemBuilder: _renderRow,
          itemCount: list.length + 1,
          controller: _scrollController,
        ),
Widget _renderRow(BuildContext context, int index) {
    if (index < list.length) {
      return ListTile(
        title: Text(list[index]),
      );
    }
    return _getMoreWidget();
  }
   

3、

/**
   * 下拉刷新方法,为list重新赋值
   */
  Future<Null> _onRefresh() async {
    await Future.delayed(Duration(seconds: 3), () {
      print('refresh');
      setState(() {
        //list = List.generate(20, (i) => '哈喽,我是新刷新的 $i');
      });
    });
  }

  /**
   * 上拉加载更多
   */
  Future _getMore() async {
    if (!isLoading) {
      setState(() {
        isLoading = true;
      });
      await Future.delayed(Duration(seconds: 1), () {
        print('加载更多');
        setState(() {
          //加载数据
          //list.addAll(List.generate(5, (i) => '第$_page次上拉来的数据'));
          _page++;
          isLoading = false;
        });
      });
    }
  }
  /**
   * 加载更多时显示的组件,给用户提示
   */
  Widget _getMoreWidget() {
    return Center(
      child: Padding(
        padding: EdgeInsets.all(10.0),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            Text(
              '加载中...',
              style: TextStyle(fontSize: 16.0),
            ),
            CircularProgressIndicator(
              strokeWidth: 1.0,
            )
          ],
        ),
      ),
    );
  }