[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