CALayer都是实现了CAMediaTiming协议（或者叫做接口）。所以layer的动画有一个很有意思的属性speed。如果一个layer的动画速度变成0.0的时候，很显然这个动画就不再动了。设置layer的speed为0时，layer的动画暂停。speed属性设置为任意大于0的值时，动画回复。
要暂停一个动画时：
-(void)pauseLayer:(CALayer*)layer { CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil]; layer.speed = 0.0; layer.timeOffset = pausedTime; }
恢复一个动画：
-(void)resumeLayer:(CALayer*)layer { CFTimeInterval pausedTime = [layer timeOffset]; layer.speed = 1.0; layer.timeOffset = 0.0; layer.beginTime = 0.0; CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime; layer.beginTime = timeSincePause; }
比如你有这么一个在ImageView上执行的动画，你想让这个动画开始执行后点击按钮暂停，在点击按钮恢复就可以这样：
CABasicAnimation *sizeAnim = [CABasicAnimation animationWithKeyPath:@"transform"]; sizeAnim.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity]; sizeAnim.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeScale(1.5f, 1.5f, 1.f)]; sizeAnim.duration = .2f; sizeAnim.fillMode = kCAFillModeForwards; sizeAnim.removedOnCompletion = YES; sizeAnim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]; [self.collectionImageView.layer addAnimation:sizeAnim forKey:@"size"]; CAKeyframeAnimation *shakeAnim = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"]; shakeAnim.values = @[@(M_PI/6), @(-M_PI/6),@(M_PI/6)/*, @(-M_PI/6)*/]; shakeAnim.timingFunctions = @[[self getTiming:kCAMediaTimingFunctionLinear] , [self getTiming:kCAMediaTimingFunctionLinear] ,[self getTiming:kCAMediaTimingFunctionLinear]]; shakeAnim.duration = .2f; // shakeAnim.beginTime = CACurrentMediaTime() + sizeAnim.duration; [self.collectionImageView.layer addAnimation:shakeAnim forKey:@"shake"];
上面说的ImageView可以通过self.collectionImageView来访问。这里设置的执行时间都不是很长，在实验的时候最好把动画的执行时间设置的长点。
暂停&恢复的代码：
static BOOL animationStoped = NO; - (IBAction)animationAction:(id)sender { if (!animationStoped) { [self pauseLayer:self.collectionImageView.layer]; // animationStoped = YES; } else{ [self resumeLayer:self.collectionImageView.layer]; } animationStoped = !animationStoped; }
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本文转自张昺华-sky博客园博客，原文链接：http://www.cnblogs.com/sunshine-anycall/p/3418685.html
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