cannot see the animation effect in ngui

hi, everyone!
i want to make a simple animation, for example, when you press an icon in your iphone for serval seconds, the icons will shake and show close button, i want to make a effect like that and play in a draggable panel which created by ngui, but when i invoke "animation.Play("xxx")", it doesn't work under the panel...but when if i drag this gameobject to a panel(not a draggable panel), it works, i have no idea..plz help..
thanks