一看就懂demo下载，地址：github
想做一个简单的动画，运用一下CAAnimation，思路是：开始两个图标重叠在一起，点击按钮，两个图标分别向两边倾斜，回到原点后交换前后位置
1.要交换前后位置那肯定是要涉及到z轴了，动画实现：
CABasicAnimation *z =
[CABasicAnimation animationWithKeyPath:@"zPosition"];
z.fromValue = @(self.indicator);
z.toValue = @(-self.indicator);
z.duration = 1;
2.往两边移动，对应属性是position，动画实现：
CAKeyframeAnimation *p =
[CAKeyframeAnimation animationWithKeyPath:@"position"];
p.values = @[[NSValue valueWithCGPoint:CGPointZero],
[NSValue valueWithCGPoint:CGPointMake(90, -20)],
[NSValue valueWithCGPoint:CGPointZero]];
p.timingFunctions =
@[[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];
p.additive = YES;
p.duration = 1;
3.倾斜的话，对应transform.rotation，动画实现：
CAKeyframeAnimation *r =
[CAKeyframeAnimation animationWithKeyPath:@"transform.rotation"];
r.values = @[@0, @0.1, @0];
r.duration = 1;
r.timingFunctions =
@[[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],
[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];
