Flutter 自定义PullToRefreshListView

Flutter 自定义PullToRefreshListView，实现下拉刷新，和上拉加载更多，以及加载到底的实现。

效果图：

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


typedef PullRefreshCallback = Future<void> Function();


///@describe 自定义ListView（下拉刷新，上拉加载更多）
///
///@author mi
///
///@time 2019/10/28
class PullToRefreshListView extends StatefulWidget {

    //item回调方法
   IndexedWidgetBuilder itemBuilder;

   //条目数
   int itemCount;

   //分割线
   Widget separatorView =  LineView(height: 4);

   //刷新回调
   PullRefreshCallback onRefresh;

   //加载更多回调
   PullRefreshCallback onMoreRefresh;

   //是否有下一页
   bool hasMore = true;

   PullToRefreshListView(
      {@required this.itemBuilder,@required this.itemCount,this.onRefresh,this.onMoreRefresh,this.hasMore});

   PullToRefreshListView.separated(
      {@required this.itemBuilder,
      @required this.itemCount,this.separatorView,this.onRefresh,this.onMoreRefresh,this.hasMore});


  @override
  State<StatefulWidget> createState() {
    return ListViewState();
  }

}

class ListViewState extends State<PullToRefreshListView>{

  ScrollController _controller;

  @override
  void initState() {
    super.initState();

    _controller = new ScrollController();
    _controller.addListener(() {

      if (_controller.position.pixels == _controller.position.maxScrollExtent) {
        if(widget.hasMore)
          widget.onMoreRefresh();
      }
    });
  }

  @override
  Widget build(BuildContext context) {

    return RefreshIndicator(
      onRefresh: widget.onRefresh,
      child: ListView.separated(
          controller: _controller,
          itemBuilder: (context, index) {
            if (index == widget.itemCount) {
              return widget.hasMore ? LoadMoreView():NoMoreView();
            } else {
              return widget.itemBuilder(context, index);
            }
          },
          separatorBuilder: (context, index) {
            return widget.separatorView;
          },
          itemCount: widget.itemCount+1),
    );
  }
}

class LoadMoreView extends StatelessWidget{

  @override
  Widget build(BuildContext context) {
    return Center(child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
      SizedBox(width: 20,height: 20,child: CircularProgressIndicator(strokeWidth: 2)),
      Padding(padding: EdgeInsets.all(10),child: Text("加载中",style: TextStyle(color: Colors.grey,fontSize: 13)))
    ]));
  }

}

class NoMoreView extends StatelessWidget{

  @override
  Widget build(BuildContext context) {
    return Container(child: Center(
        child: Padding(padding: EdgeInsets.all(2),
            child: Text("到底啦！",style: TextStyle(color: Colors.grey,fontSize: 13)))));
  }

}


///@describe LineView
///
///@author mi
///
///@time 2019/9/10
class LineView extends StatelessWidget{

  double height;
  LineView({this.height = 10});

  @override
  Widget build(BuildContext context) {
    return  Container(color: Colors.grey[200],height: height);
  }

}

调用：

PullToRefreshListView(
        itemBuilder: (context, index) => _itemView(context, index),
        itemCount: data.length,
        onRefresh: _onRefresh,
        onMoreRefresh: _onMoreRefresh,
        hasMore: _hasMore,
      )