视图唤醒时 UIView.animate() 冻结

Question

I'm infinitely looping a UIView animation with the following

UIView.animate(withDuration: 1.0, delay: 0, options: [.autoreverse, .repeat], animations: {
        self.someLabel.alpha = 0.3
    }, completion: nil)

This works fine but when the viewController wakes up the animation freezes where it is.

Running the same code as above in viewDidWakeUp() doesn't fix it.

How can I make the animation either not freeze, or continue where it left off when the viewController wakes up.

To clarify, by 'wake up' I mean either of the following:

• Closing the app and opening it again, with this viewController active,
• Sleeping the phone and then waking it with this viewController still active

Answer 1

Add two notification willEnterForegroundNotification and didEnterBackgroundNotification.

It is also worth noting. That in some cases, you need to reset the animated property to get the new animation to stick. I can confirm this with an animated transformation.

Just calling...

 view.layer.removeAllAnimations()
 self.someLabel.alpha = 1.0

//Complete code

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view, typically from a nib.

    NotificationCenter.default.addObserver(self, selector:#selector(didEnterForeground) , name: UIApplication.willEnterForegroundNotification, object: nil)

    NotificationCenter.default.addObserver(self, selector:#selector(didEnterBackground) , name: UIApplication.didEnterBackgroundNotification, object: nil)

}

@objc  func didEnterBackground() {
    view.layer.removeAllAnimations()
    self.someLabel.alpha = 1.0
}


@objc func didEnterForeground()  {

    DispatchQueue.main.async {
        self.animation()
    }

}
func animation() {

    UIView.animate(withDuration: 1.0, delay: 0, options: [.autoreverse, .repeat], animations: {
        self.someLabel.alpha = 0.3
    }, completion: nil)
}