public override bool OnKeyDown([GeneratedEnum]Android.Views.Keycode keyCode, KeyEvent e)

        {

            switch (keyCode)

            {

                case Android.Views.Keycode.VolumeUp:

                    Message.ShortAlert("音量上键按下");//Toast显示

                    break;

                case Android.Views.Keycode.VolumeDown:

                    Message.ShortAlert("音量下键按下");//Toast显示

                    break;

                default:break;

            }

            return true;//屏蔽原有功能

            //return base.OnKeyDown(keyCode, e);//不屏蔽原有功能

        }