Changing opacity during keyframe animation Swift

Question

I am trying to animate a few circles and changing their opacities simultaneously.

        UIView.animateKeyframesWithDuration(2, delay: 0, options: .Repeat, animations: {
        UIView.addKeyframeWithRelativeStartTime(0, relativeDuration: 0.5, animations: {
            self.innerRingView.alpha = 1
        })
        UIView.addKeyframeWithRelativeStartTime(0.5, relativeDuration: 0.5, animations: {
            self.innerRingView.alpha = 0
            self.middleRingView.alpha = 1
        })
        UIView.addKeyframeWithRelativeStartTime(1, relativeDuration: 0.5, animations: {
            self.middleRingView.alpha = 0
            self.outterRingView.alpha = 1
        })
        UIView.addKeyframeWithRelativeStartTime(1.5, relativeDuration: 0.5, animations: {
            self.outterRingView.alpha = 0
        })
        }, completion: nil)

For some reason, it never gets to the second animation:

UIView.addKeyframeWithRelativeStartTime(1, relativeDuration: 0.5, animations: {
        self.middleRingView.alpha = 0
        self.outterRingView.alpha = 1
    })

Because of this, my animation isn't work. innerRingView never goes back to 0 opacity and outterRingView never appears (all the views are set to 0 alpha by default).

What seems to be the problem here?

ldindu · Accepted Answer · 2016-07-19 22:43:59Z

3

Issue appeared to be with your key frame relative start time

UIView.addKeyframeWithRelativeStartTime

which must be be in the range 0 to 1, where 0 represents the start of the overall animation and 1 represents the end of the overall animation. For example, for an animation that is two seconds in duration, specifying a start time of 0.5 causes the animations to begin executing one second after the start of the overall animation.

answered Jul 19, 2016 at 22:43

ldindu

4,3902 gold badges22 silver badges24 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Duncan C Over a year ago

Idindu beat me to it. (Voted.) Relative start times must be in the range 0 (beginning of the entire animation) and 1 (the very end of the animation)

Bob Over a year ago

So if I want the whole animation to be 2 seconds long. Should my keyframe relative start times be a ratio of 2? So 0, 0.25, 0.5, 0.75?

ldindu Over a year ago

The time taken by each animation block is relative to the whole duration and you need to ensure that the start times are correct by tracking cumulative time. Your ratio, AFAIK, doesn't need to be a ratio of 2 but within whole duration of 2, the actual animation interpolates between them which is guided by the options parameter.

ldindu Over a year ago

You can define 0, 0.25, 0.5, 0.75 but you need to accommodate your keyframe's relativeDuration accordingly. 0.25 would be better for your example.

Collectives™ on Stack Overflow

Changing opacity during keyframe animation Swift

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related