按option后会有提示：Do not use the label object to set the text color or the shadow color. Instead, use the setTitleColor:forState: and setTitleShadowColor:forState: methods of this class to make those changes.
设置button的字体颜色要用 setTitleColor:forState:
为什么alertView弹出后button会消失的问题,布布扣,bubuko.com
原文：http://www.cnblogs.com/ejllen/p/3752426.html