How to set animation for button background

I have button and I have two pictures green.png and red开发者_运维百科.png. How to achieve that when button is visible to change button background every 500 ms ( green.png=>red.png=>green.png=>red.png...) ?

try to use AnimationDrawable

http://developer.android.com/reference/android/graphics/drawable/AnimationDrawable.html

Hope it help you!