aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

Question

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

Answer 1

防止Bad state: No element异常，当你的列表为空时，可以处理列表没有元素的情况。具体来说，删除所有元素后，您可以检查列表是否为空，并有条件地在 ExpansionTile 内显示不同的小部件（例如占位符或空状态消息）。以下是修改代码的方法：

   class GroupsNew extends StatefulWidget {
  const GroupsNew({super.key});

  @override
  State<GroupsNew> createState() => _GroupsNewState();
}

class _GroupsNewState extends State<GroupsNew> {
  bool _customIcon = false;
  List<String> test = ["string"];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Groups')),
      body: Padding(
        padding: const EdgeInsets.all(14.0),
        child: ExpansionTile(
          title: Text('Expandable List'),
          trailing: Icon(_customIcon ? Icons.expand_less : Icons.expand_more),
          onExpansionChanged: (bool expanded) {
            setState(() => _customIcon = expanded);
          },
          children: test.isNotEmpty
              ? test
                  .map((item) => ListTile(
                        title: Text(item, style: TextStyle(fontSize: 20)),
                        trailing: IconButton(
                          icon: Icon(Icons.delete),
                          onPressed: () {
                            setState(() {
                              test.remove(item);
                            });
                          },
                        ),
                      ))
                  .toList()
              : [
                  ListTile(
                    title: Text(
                      'No items available',
                      style: TextStyle(fontSize: 16, fontStyle: FontStyle.italic),
                    ),
                  ),
                ],
        ),
      ),
    );
  }
}