import 'package:flutter/material.dart';
/// 數(shù)據(jù)源 
/// https://github.com/yixiaolunhui/flutter_xy
class ItemBean {
  final String groupName;
  final List<String> items;
  const ItemBean({required this.groupName, this.items = const []});
  static List<ItemBean> get groupListData => const [
    ItemBean(groupName: '水果', items: [
      '蘋果', '香蕉', '橙子', '葡萄', '芒果', '梨', '桃子', '草莓', '西瓜', '檸檬',
      '菠蘿', '櫻桃', '藍(lán)莓', '獼猴桃', '李子', '柿子', '杏', '楊梅', '石榴', '木瓜'
    ]),
    ItemBean(groupName: '動物', items: [
      '狗', '貓', '獅子', '老虎', '大象', '熊', '鹿', '狼', '狐貍', '猴子',
      '企鵝', '熊貓', '袋鼠', '海豚', '鯊魚', '斑馬', '長頸鹿', '鱷魚', '孔雀', '烏龜'
    ]),
    ItemBean(groupName: '職業(yè)', items: [
      '醫(yī)生', '護士', '教師', '工程師', '程序員', '律師', '會計', '警察', '消防員', '廚師',
      '司機', '飛行員', '科學(xué)家', '記者', '設(shè)計師', '作家', '演員', '音樂家', '畫家', '攝影師'
    ]),
    ItemBean(groupName: '菜譜', items: [
      '紅燒肉', '糖醋排骨', '宮保雞丁', '麻婆豆腐', '魚香肉絲', '酸辣湯', '蒜蓉菠菜', '回鍋肉', '水煮魚', '烤鴨',
      '蛋炒飯', '蠔油生菜', '紅燒茄子', '西紅柿炒雞蛋', '油燜大蝦', '香菇雞湯', '酸菜魚', '麻辣香鍋', '鐵板牛肉', '干煸四季豆'
    ]),
  ];
}
/// 分組列表
class GroupListPage extends StatelessWidget {
  const GroupListPage({super.key});
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('分組列表')),
      body: CustomScrollView(
        slivers: ItemBean.groupListData.map(_buildGroup).toList(),
      ),
    );
  }
  Widget _buildGroup(ItemBean itemBean) {
    return SliverMainAxisGroup(
      slivers: [
        SliverPersistentHeader(
          pinned: true,
          delegate: HeaderDelegate(itemBean.groupName),
        ),
        SliverList(
          delegate: SliverChildBuilderDelegate(
            (_, index) => _buildItemByUser(itemBean.items[index]),
            childCount: itemBean.items.length,
          ),
        ),
      ],
    );
  }
  Widget _buildItemByUser(String item) {
    return Container(
      alignment: Alignment.center,
      height: 50,
      child: Row(
        children: [
          const Padding(
            padding: EdgeInsets.only(left: 20, right: 10.0),
            child: FlutterLogo(size: 30),
          ),
          Text(
            item,
            style: const TextStyle(fontSize: 16),
          ),
        ],
      ),
    );
  }
}
class HeaderDelegate extends SliverPersistentHeaderDelegate {
  final String title;
  const HeaderDelegate(this.title);
  @override
  Widget build(
      BuildContext context, double shrinkOffset, bool overlapsContent) {
    return Container(
      alignment: Alignment.centerLeft,
      color: Colors.grey,
      padding: const EdgeInsets.only(left: 20),
      height: 40,
      child: Text(title, style: const TextStyle(fontSize: 16)),
    );
  }
  @override
  double get maxExtent => 40;
  @override
  double get minExtent => 40;
  @override
  bool shouldRebuild(covariant HeaderDelegate oldDelegate) {
    return title != oldDelegate.title;
  }
}