这里有一个例子。用主题 Package PopupMenuButton。

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

  @override
  State<PopupMenuExample> createState() => _PopupMenuExampleState();
}

class _PopupMenuExampleState extends State<PopupMenuExample> {
  int? selectedMenu;

  @override
  Widget build(BuildContext context) {
    return Theme(
      data: Theme.of(context).copyWith(
        highlightColor: Colors.lightBlueAccent,
      ),
      child: PopupMenuButton<int>(
        icon: const Icon(
          Icons.swap_vert,
          size: 26,
          color: Color(0xffffffff),
        ),
        initialValue: selectedMenu,
        // Callback that sets the selected popup menu item.
        onSelected: (int item) {
          setState(() {
            selectedMenu = item;
          });
        },
        itemBuilder: (BuildContext context) => <PopupMenuEntry<int>>[
          const PopupMenuItem<int>(
            value: 0,
            child: Text('Example 1'),
          ),
          const PopupMenuItem<int>(
            value: 1,
            child: Text('Example 2'),
          ),
          const PopupMenuItem<int>(
            value: 2,
            child: Text('Example 3'),
          ),
        ],
      ),
    );
  }

}