Persisting CABasicAnimation - swift

Question

I'm using an extension I found online to persist a CABasicAnimation that I'm using for my app; the code for that is below. It works and the animation does persist in the sense that the animation layer is not totally removed from the screen, but the issue I'm having is that if the timer is running and the countdown animation has begun and the user leaves the app at 10 seconds lets say and enters back at 15 seconds, the animation continues from 10 seconds but the actual count is ahead.
public class LayerPersistentHelper {
private var persistentAnimations: [String: CAAnimation] = [:]
private var persistentSpeed: Float = 0.0
private weak var layer: CALayer?
public init(with layer: CALayer) {
self.layer = layer
addNotificationObservers()
}
deinit {
removeNotificationObservers()
}}
private extension LayerPersistentHelper {
func addNotificationObservers() {
let center = NotificationCenter.default
let enterForeground = UIApplication.willEnterForegroundNotification
let enterBackground = UIApplication.didEnterBackgroundNotification
center.addObserver(self, selector: #selector(didBecomeActive), name: enterForeground, object: nil)
center.addObserver(self, selector: #selector(willResignActive), name: enterBackground, object: nil)
}
func removeNotificationObservers() {
NotificationCenter.default.removeObserver(self)
}
func persistAnimations(with keys: [String]?) {
guard let layer = self.layer else { return }
keys?.forEach { (key) in
if let animation = layer.animation(forKey: key) {
persistentAnimations[key] = animation
}
}
}
func restoreAnimations(with keys: [String]?) {
guard let layer = self.layer else { return }
keys?.forEach { (key) in
if let animation = persistentAnimations[key] {
layer.add(animation, forKey: key)
}
}
}}
#objc extension LayerPersistentHelper {
func didBecomeActive() {
guard let layer = self.layer else { return }
restoreAnimations(with: Array(persistentAnimations.keys))
persistentAnimations.removeAll()
if persistentSpeed == 1.0 { // if layer was playing before background, resume it
layer.resumeAnimations()
}
}
func willResignActive() {
guard let layer = self.layer else { return }
persistentSpeed = layer.speed
layer.speed = 1.0 // in case layer was paused from outside, set speed to 1.0 to get all animations
persistAnimations(with: layer.animationKeys())
layer.speed = persistentSpeed // restore original speed
layer.pauseAnimations()
}}
public extension CALayer {
var isAnimationsPaused: Bool {
return speed == 0.0
}
static var timeElapsed: Double = 0
func pauseAnimations() {
if !isAnimationsPaused {
let currentTime = CACurrentMediaTime()
let pausedTime = convertTime(currentTime, from: nil)
speed = 0.0
timeOffset = pausedTime
}
}
func resumeAnimations() {
let pausedTime = timeOffset
speed = 1.0
timeOffset = 0.0
beginTime = 0.0
let currentTime = CACurrentMediaTime()
let timeSincePause = convertTime(currentTime, from: nil) - pausedTime
beginTime = timeSincePause
}}
extension CALayer. {
static private var persistentHelperKey = "progressAnim"
func makeAnimationsPersistent() {
var object = objc_getAssociatedObject(self, &CALayer.persistentHelperKey)
if object == nil {
object = LayerPersistentHelper(with: self)
let nonatomic = objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC
objc_setAssociatedObject(self, &CALayer.persistentHelperKey, object, nonatomic)
}
}}
Any Ideas?

Answer 1

If anyone has this issue I found that setting the begin time equal to
beginTime = convertTime(timeOffset, from: nil)
does the trick