通过转储Apple的 MKUserLocationView的动画，我能够看到他们是如何做到的。事实证明这是 CAAnimationGroup 的用途。通过将2秒动画封装到5秒动画组中，您最终会得到2秒动画，然后是3秒延迟：

By dumping the animations of Apple's MKUserLocationView, I was able to see how they were doing it. Turns out that this is what CAAnimationGroup is for. By encapsulating a 2 seconds animation into a 5 seconds animation group, you'll end up with a 2 seconds animation followed by a 3 seconds delay:

CAAnimationGroup *animationGroup = [CAAnimationGroup animation];
animationGroup.duration = 5;
animationGroup.repeatCount = INFINITY;

CAMediaTimingFunction *easeOut = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

CABasicAnimation *pulseAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale.xy"];
pulseAnimation.fromValue = @0.0;
pulseAnimation.toValue = @1.0;
pulseAnimation.duration = 2;
pulseAnimation.timingFunction = easeOut;

animationGroup.animations = @[pulseAnimation];

[ringImageView.layer addAnimation:animationGroup forKey:@"pulse"];