CABasicAnimation animationWithKeyPath 的类型

[CABasicAnimation animationWithKeyPath:@"position"];

animationWithKeyPath后面的属性不能随便填，它必须是CALayer的某项属性，你下面写的代码才会对应的去执行改变该属性的效果。

animationWithKeyPath的值：

opacity

margin

zPosition

backgroundColor

cornerRadius

borderWidth 

bounds

contents

contentsRect

cornerRadius

frame

hidden

mask

masksToBounds

opacity

position

shadowColor

shadowOffset

shadowOpacity

shadowRadius