flutter CheckedPopupMenuItem在选择项目后保持菜单打开

class MyMenu extends StatefulWidget {
  @override
  _MyMenuState createState() => _MyMenuState();
}

class _MyMenuState extends State<MyMenu> {
  bool _isOpen = false;
  String _selectedItem;

  void _handleMenuItemSelected(String value) {
    setState(() {
      _selectedItem = value;
      _isOpen = true; // 保持菜单打开
    });
  }

  @override
  Widget build(BuildContext context) {
    return PopupMenuButton<String>(
      onSelected: _handleMenuItemSelected,
      itemBuilder: (BuildContext context) => <PopupMenuEntry<String>>[
        CheckedPopupMenuItem<String>(
          value: 'item1',
          checked: _selectedItem == 'item1',
          child: Text('Item 1'),
        ),
        CheckedPopupMenuItem<String>(
          value: 'item2',
          checked: _selectedItem == 'item2',
          child: Text('Item 2'),
        ),
      ],
      child: ListTile(
        title: Text('Open Menu'),
      ),
    );
  }
}