lift-app/lib/widgets/my_refresh_list.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 MyListView extends StatefulWidget {
  const MyListView({
    Key key,
    @required this.itemCount,
    @required this.itemBuilder,
    @required this.onRefresh,
    this.loadMore,
    this.normal: true,
    this.hasMore: false,
    this.stateType: StateType.empty,
    this.pageSize: 10,
    this.padding,
    this.itemExtent,
    this.showSeparator = true,
  }) : super(key: key);

  final RefreshCallback onRefresh;
  final LoadMoreCallback loadMore;
  final int itemCount;
  final bool hasMore;
  final bool normal;
  final IndexedWidgetBuilder itemBuilder;
  final StateType stateType;

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

  final bool showSeparator;

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

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

class _MyListViewState extends State<MyListView> {
  /// 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，且滑动至底部
          if (note.metrics.pixels == note.metrics.maxScrollExtent &&
              note.metrics.axis == Axis.vertical) {
            _loadMore();
          }
          return true;
        },
        child: RefreshIndicator(
            onRefresh: widget.onRefresh,
            child: widget.itemCount == 0
                ? (widget.normal
                    ? StateLayout(type: widget.stateType)
                    : Container(
                        child: null,
                      ))
                : ListView.separated(
                    shrinkWrap: true,
                    itemCount: widget.loadMore == null
                        ? widget.itemCount
                        : widget.itemCount + 1,
                    padding: widget.padding,
                    // itemExtent: widget.itemExtent,
                    separatorBuilder: (context, index) => widget.showSeparator ? Divider(
                          height: 0.5,
                          thickness: .5,
                        ) : Container(),
                    itemBuilder: (BuildContext context, int index) {
                      /// 不需要加载更多则不需要添加FootView
                      if (widget.loadMore == null) {
                        return widget.itemBuilder(context, index);
                      } else {
                        return index < widget.itemCount
                            ? widget.itemBuilder(context, index)
                            : MoreWidget(widget.itemCount, widget.hasMore,
                                widget.pageSize);
                      }
                    })),
      ),
    );
  }

  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: Colors.transparent,
      child: Padding(
        padding: EdgeInsets.symmetric(vertical: 10),
        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),
          ],
        ),
      ),
    );
  }
}