ios developer core animation programming guide - advanced animation tricks
- pausing and resuming animations
func pauseAnimation() {
let pausedTime = layer.convertTime(CACurrentMediaTime(), fromLayer: nil)
layer.speed = 0
layer.timeOffset = pausedTime
}
func resumeAnimation() {
let pausedTime = layer.timeOffset
layer.speed = 1
layer.timeOffset = 0
layer.beginTime = 0
let timeSincePause = layer.convertTime(CACurrentMediaTime(), fromLayer: nil) - pausedTime
layer.beginTime = timeSincePause
}
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