UIButton set BackgroundColor use Core Animation

原文出處

http://www.cimgf.com/2010/01/28/fun-with-uibuttons-and-core-animation-layers/

Colorful Button Demo Project

有個很好的翻譯者link

http://itouchs.blogspot.tw/2010/10/iphone-08-setting-background-color-for.html