TDDropdownMenu _buildUp(BuildContext context) {
  return TDDropdownMenu(
    direction: TDDropdownMenuDirection.up,
    onMenuOpened: (value) {
      print('打开第$value个菜单');
    },
    onMenuClosed: (value) {
      print('关闭第$value个菜单');
    },
    builder: (context) {
      return [
        TDDropdownItem(
          options: [
            TDDropdownItemOption(label: '全部产品', value: 'all', selected: true),
            TDDropdownItemOption(label: '最新产品', value: 'new'),
            TDDropdownItemOption(label: '最火产品', value: 'hot'),
          ],
          onChange: (value) {
            print('选择：$value');
          },
        ),
        TDDropdownItem(
          options: [
            TDDropdownItemOption(label: '默认排序', value: 'default', selected: true),
            TDDropdownItemOption(label: '价格从高到低', value: 'price'),
          ],
        ),
      ];
    },
  );
}