How to pause the animation of a layer tree-优快云博客

本文介绍了如何通过调整CALayer的速度和时间偏移属性来暂停和恢复层树中的所有动画。这种方法利用了CALayer遵循的CAMediaTiming协议，通过设置speed为0.0并记录暂停时间来实现暂停效果，再通过调整speed和timeOffset恢复动画。

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https://developer.apple.com/library/ios/qa/qa1673/_index.html

Technical Q&A QA1673

How to pause the animation of a layer tree

Q: How do I pause all animations in a layer tree?

A: In order to pause animations in a layer tree, you can take advantage of the fact that a CALayer conforms to the CAMediaTiming protocol. The CAMediaTiming protocol defines, among other things, a speed with which its timeline progresses, which you can use to pause all animations on the target layer. Listing 1 demonstrates how you can do this.

Listing 1 Pause and Resume animations.

-(void)pauseLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
    layer.speed = 0.0;
    layer.timeOffset = pausedTime;
}

-(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;
}

转载于:https://my.oschina.net/michael1986/blog/190966