fun-selfie-app/lib/widgets/my_refresh_list.dart

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

/// 封装下拉刷新与加载更多
class DeerListView extends StatefulWidget {
  const DeerListView({
    super.key,
    required this.itemCount,
    required this.itemBuilder,
    required this.onRefresh,
    this.loadMore,
    this.hasMore = false,
    this.padding,
    this.controller,
  });

  final RefreshCallback onRefresh;
  final LoadMoreCallback? loadMore;
  final int itemCount;
  final bool hasMore;
  final IndexedWidgetBuilder itemBuilder;
  final ScrollController? controller;

  /// padding属性使用时注意会破坏原有的SafeArea，需要自行计算bottom大小
  final EdgeInsetsGeometry? padding;

  @override
  State<StatefulWidget> createState() => _DeerListViewState();
}

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

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

  @override
  Widget build(BuildContext context) {
    final Widget child = RefreshIndicator(
      onRefresh: widget.onRefresh,
      child:
          // widget.itemCount == 0 ?
          // StateLayout(type: widget.stateType) :
          ListView.separated(
        controller: widget.controller,
        itemCount:
            widget.loadMore == null ? widget.itemCount : widget.itemCount + 1,
        padding: widget.padding,
        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);
          }
        },
        separatorBuilder: (context, index) {
          return const Divider();
        },
      ),
    );
    return SafeArea(
      child: NotificationListener<ScrollNotification>(
        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: child,
      ),
    );
  }

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

class MoreWidget extends StatelessWidget {
  const MoreWidget(this.itemCount, this.hasMore, {super.key});

  final int itemCount;
  final bool hasMore;

  @override
  Widget build(BuildContext context) {
    TextStyle style = const TextStyle(color: Color(0x8A000000));
    return Padding(
      padding: const EdgeInsets.symmetric(vertical: 10.0),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          if (hasMore) const CupertinoActivityIndicator(),
          Text(hasMore ? '正在加载中...' : '没有了呦~', style: style),
        ],
      ),
    );
  }
}