xamarin studio 中SpinButton ComBox Splid 鼠标放上去就会自动接收焦点，然后进行数值变化

 [System.ComponentModel.ToolboxItem(true)]
    public class SpinButtonEx : Gtk.SpinButton
    {
        bool isPress = false;
        public SpinButtonEx(double min = int.MinValue, double max = int.MaxValue, double step = 1)
            : base(min, max, step)
        {
            this.Numeric = false;
        }

        protected override void OnFocusGrabbed()
        {
            if (isPress) this.CanFocus = true;
            else this.CanFocus = false;
            base.OnFocusGrabbed();
        }

        protected override bool OnScrollEvent(Gdk.EventScroll evnt)
        {
            if (!this.IsFocus) return false;
            return base.OnScrollEvent(evnt);
        }

        protected override bool OnButtonPressEvent(Gdk.EventButton evnt)
        {
            if (evnt.Button == 1) isPress = true;
            return base.OnButtonPressEvent(evnt);
        }

        protected override bool OnFocusOutEvent(Gdk.EventFocus evnt)
        {
            isPress = false;
            return base.OnFocusOutEvent(evnt);
        }