为了实现某些提示框更好警示的作用，需要加入抖动的效果。       具体做法：抖动就是先变大再变小，最后恢复原样的涡阳，再通过关键帧动画，定义每一段动画的效果和经历时间，即可实现对应效果。

CAKeyframeAnimation *popAnimation = [CAKeyframeAnimation animationWithKeyPath:@"transform"];    popAnimation.duration = 0.4;    popAnimation.values = @[[NSValue valueWithCATransform3D:CATransform3DMakeScale(0.01f, 0.01f, 1.0f)],                            [NSValue valueWithCATransform3D:CATransform3DMakeScale(1.1f, 1.1f, 1.0f)],                            [NSValue valueWithCATransform3D:CATransform3DMakeScale(0.9f, 0.9f, 1.0f)],                            [NSValue valueWithCATransform3D:CATransform3DIdentity]];    popAnimation.keyTimes = @[@0.2f, @0.5f, @0.75f, @1.0f];    popAnimation.timingFunctions = @[[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],                                     [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut],                                     [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];    [_mainView.layer addAnimation:popAnimation forKey:nil];复制代码

效果图如下：