使用picker，当我选择之后，导航栏的背景就会变，本来是白色的导航栏，会变成默认的好像

`Picker picker = Picker(
      adapter: NumberPickerAdapter(data: [
        const NumberPickerColumn(
          begin: 14,
          end: 99,
          initValue: 18,
          suffix: Text(" 岁"),
        ),
      ]),
      headerDecoration: const BoxDecoration(
        border: Border(bottom: BorderSide(color: Colors.black12, width: 0.5)),
      ),
      hideHeader: true,
    );`