CAanimation动画 暂停，继续

暂停：

let pausedTime = layer.convertTime(CACurrentMediaTime(), fromLayer: nil)  
layer.speed = 0.0  
layer.timeOffset = pausedTime 

继续：

    let pausedTime = layer.timeOffset  
    layer.speed = 1.0  
    layer.timeOffset = 0.0  
    layer.beginTime = 0.0  
    let timeSincePause = layer.convertTime(CACurrentMediaTime(), fromLayer: nil) - pausedTime  
    layer.beginTime = timeSincePause  

参考:http://blog.csdn.net/yongyinmg/article/details/39673665