Understanding animateKeyframes relative start / delay time

Question

I'm either stupid or misunderstood how keyframe animation works on iOS (or both!). The two animation blocks below give different results, but I expect them to be the same:

let duration: TimeInterval = 2

UIView.animateKeyframes(withDuration: duration, delay: 0, animations: {
    UIView.addKeyframe(withRelativeStartTime: 0.9, relativeDuration: 0.1, animations: {
        self.someView.transform = CGAffineTransform(translationX: 0, y: 150)
    })
})

UIView.animateKeyframes(withDuration: duration * 0.1, delay: duration * 0.9, animations: {
    UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 1, animations: {
        self.someView.transform = CGAffineTransform(translationX: 0, y: 150)
    })
})

Can someone help me understand why this is happening at execution? The first seems to do what I expect, but the second seems to do the animation sooner than expected.

Answer 1

. - 0,2 2 , - 0,2 . , .

, :

UIView.animate(withDuration: duration, delay: 0, options: [.curveLinear], animations: {
    UIView.animateKeyframes(withDuration: duration, delay: 0, options: [.overrideInheritedDuration, .calculationModeLinear], animations: {
        UIView.addKeyframe(withRelativeStartTime: 0.9, relativeDuration: 0.1, animations: {
            view1.transform = CGAffineTransform(translationX: 0, y: 150)
        })
    })

    UIView.animateKeyframes(withDuration: duration * 0.1, delay: duration * 0.9, options: [.overrideInheritedDuration, .calculationModeLinear], animations: {
        UIView.addKeyframe(withRelativeStartTime: 0, relativeDuration: 1, animations: {
            view2.transform = CGAffineTransform(translationX: 0, y: 150)
        })
    })
}, completion: nil)

, , , , :)