How to use CAKeyframeAnimation?

Question

I'm studying animation and I want to use CAKeyframeAnimation. On Apple Developer I found the following code snippet:

let colorKeyframeAnimation = CAKeyframeAnimation(keyPath: "backgroundColor")

colorKeyframeAnimation.values = [
    UIColor.red.cgColor,
    UIColor.green.cgColor,
    UIColor.blue.cgColor
]
colorKeyframeAnimation.keyTimes = [0, 0.5, 1]
colorKeyframeAnimation.duration = 2

But I have not found solution about how to add this animation object to view. How to make it work and apply to anything?

Answer 1

You add it to the view’s layer with add(_:forKey:).

---

Alternatively, if you don't want to animate with CoreAnimation, you can use the UIView.animateKeyframes API, e.g.:

// if the animatedView isn't already .red, set it as such
//
// animatedView.backgroundColor = .red

// then start your animation from the current color, to green, to blue

UIView.animateKeyframes(withDuration: 2, delay: 0, options: [], animations: { 
    UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 0.5, animations: { 
        self.animatedView.backgroundColor = .green
    })
    UIView.addKeyframe(withRelativeStartTime: 0.5, relativeDuration: 0.5, animations: { 
        self.animatedView.backgroundColor = .blue
    })
}, completion: nil)

Note, the "relative" start time and duration values are a percentage of the overall animation duration.