lift-app/lib/widgets/chat_list_view.dart

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

import 'package:liftmanager/res/resources.dart';
import 'package:liftmanager/utils/theme_utils.dart';
import 'package:liftmanager/widgets/state_layout.dart';

/// 封装下拉刷新与加载更多
class ChatListView extends StatefulWidget {
  const ChatListView({
    Key key,
    @required this.itemCount,
    @required this.itemBuilder,
    @required this.onRefresh,
    this.loadMore,
    this.hasMore: false,
    this.pageSize: 10,
    this.padding,
    this.itemExtent,
    this.scrollController,
  }) : super(key: key);
  final RefreshCallback onRefresh;
  final LoadMoreCallback loadMore;
  final int itemCount;
  final bool hasMore;
  final IndexedWidgetBuilder itemBuilder;

  /// 一页的数量，默认为10
  final int pageSize;
  final EdgeInsetsGeometry padding;
  final double itemExtent;
  final ScrollController scrollController;

  @override
  _ChatListViewState createState() => _ChatListViewState();
}

typedef RefreshCallback = Future<void> Function();
typedef LoadMoreCallback = Future<void> Function();

class _ChatListViewState extends State<ChatListView> {
  /// 是否正在加载数据
  bool _isLoading = false;

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: NotificationListener(
        onNotification: (ScrollNotification note) {
          /// 确保是垂直方向滚动，且滑动至顶部
          // if (note.metrics.pixels == note.metrics.maxScrollExtent && note.metrics.axis == Axis.vertical){
          if (note.metrics.pixels == 0.0 &&
              note.metrics.axis == Axis.vertical &&
              note.metrics.maxScrollExtent != 0.0 &&
              note.metrics.extentBefore == 0.0) {
            print("到顶了。。。");
          }
          ScrollMetrics metrics = note.metrics;
          // print(metrics.pixels);// 当前位置
          // print(metrics.atEdge);//是否在顶部或底部
          // print(metrics.axis);//垂直或水平滚动
          // print(metrics.axisDirection);// 滚动方向是down还是up
          // print(metrics.extentAfter);//视口底部距离列表底部有多大
          // print(metrics.extentBefore);//视口顶部距离列表顶部有多大
          // print(metrics.extentInside);//视口范围内的列表长度
          // print(metrics.maxScrollExtent);//最大滚动距离，列表长度-视口长度
          // print(metrics.minScrollExtent);//最小滚动距离
          // print(metrics.viewportDimension);//视口长度
          // print(metrics.outOfRange);//是否越过边界
          // print('------------------------');
          return true;
        },
        child: RefreshIndicator(
          displacement: 1.0,
          onRefresh: widget.onRefresh,
          child: ListView.builder(
              // shrinkWrap: true,
              itemCount: widget.itemCount,
              controller: widget.scrollController,
              reverse: false,
              physics: new AlwaysScrollableScrollPhysics(),
              padding: widget.padding,
              itemExtent: widget.itemExtent,
              itemBuilder: (BuildContext context, int index) {
                  return widget.itemBuilder(context, index);
              }),
        ),
      ),
    );
  }

  Future _loadMore() async {
    if (widget.loadMore == null) {
      return;
    }
    if (_isLoading) {
      return;
    }
    if (!widget.hasMore) {
      return;
    }
    _isLoading = true;
    await widget.loadMore();
    _isLoading = false;
  }
}

class MoreWidget extends StatelessWidget {
  const MoreWidget(this.itemCount, this.hasMore, this.pageSize);

  final int itemCount;
  final bool hasMore;
  final int pageSize;

  @override
  Widget build(BuildContext context) {
    final style = const TextStyle(color: Color(0xff666666));
    return Container(
      color: ThemeUtils.getTabsBg(context),
      child: Padding(
        padding: EdgeInsets.only(top: 10, bottom: 30),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            hasMore ? const CupertinoActivityIndicator() : Gaps.empty,
            hasMore ? Gaps.hGap5 : Gaps.empty,

            /// 只有一页的时候，就不显示FooterView了
            Text(hasMore ? '正在加载中...' : (itemCount < pageSize ? '' : '没有了呦~'),
                style: style),
          ],
        ),
      ),
    );
  }
}