Delay in key frame animation when running first time

Question

I am using key frame animation to animate a sequence of images. But when I run it for the first time there is a delay before animation begins. After that it runs smoothly. I tried force loading all images. It reduced delay but it is still visible. How can I further reduce the delay.

Answer 1

Consider pre-loading your images in a NSArray. Your delay is most likely caused by the fact that it first has to load the images.

So , basically , let's say you have img1.png , img2.png , etc up to img10.png:

//do this before your keyframe animation.

NSMutableArray *frames = [NSMutableArray array];
for(int i = 1 ; i <= 10 ; i++)
    [frames addObject:[UIImage imageNamed:[NSString stringWithFormat:@"img%d.png" , i]]];

//now use this array for the animation

Hope this helps. Cheers!

Answer 2

Apple is notorious for using "lazy" loading techniques, and its quite possible that putting an image retrieved from "[UIImage imageNamed:]" does not in fact create a cached bitmap, just the receipt to create it.

If all else fails try a brute force approach: force the system to render it by rendering the image in a context you then just throw away.

CGSize bigSize; // MAX width and height of your images

UIGraphicsBeginImageContextWithOptions(bigSize, YES, 0);
CGContextRef context = UIGraphicsGetCurrentContext();

for(UIImage *image in arrayOfImages) {
    CGContextDrawImage(context, (CGRect){ {0,0}, image.size }, [image CGImage]);
}
UIGraphicsEndImageContext();

Now you not only have a reference to the images, but they have been forced to render, and so hopefully the system keeps that internal bitmap around. Should be an easy test for you to make.

Answer 3

I had this problem recently and solved it by 'prerunning' the animation as early as possible with a duration of 0 and not removing it on completion. By the time I actually want to run it, the whole sequence is loaded and smooth

let animation: CAKeyframeAnimation = CAKeyframeAnimation(keyPath: "contents")
    animation.calculationMode = kCAAnimationDiscrete
    animation.duration = 0
    animation.values = spritesArray
    animation.repeatCount = 1
    animation.removedOnCompletion = false
    animation.fillMode = kCAFillModeForwards
    layer.addAnimation(animation, forKey: "animateIn")

In my case I actually had split the sequence into 2 separate keyframe animations for intro/outro and the outro was always stalling before starting. Preloading the whole thing first in a 0 duration keyframe animation prevented that.

Answer 4

This code is to swift 2.2!

Try to put a final image of you want before the animations end.

It's more like:

// the animation key is for retrive the informations about the array images
func animation(cicleTime:Int, withDuration: Double, animationKey:String){

    var images = [UIImage]()


    // get all images for animation
    for i in 0...cicleTime {
        let fileName = String(format: "image%d",i)
        let image = UIImage(named: fileName)

        images.append(image!)
    }

    let animation = CAKeyframeAnimation(keyPath: "contents")

    animation.setValue(animationKey, forKey: "animationName")

    animation.duration = withDuration
    animation.repeatCount = 1 // times you want to repeat the animation
    animation.values = images.map{$0.CGImage as! AnyObject}
    animation.delegate = self
    images.removeAll(keepCapacity: false)
    YourViewHere.layer.addAnimation(animation, forKey: "contents")

    YourViewHere.image = UIImage(named: "nameOfYourLastImageOfAnimation")
}

Well, this works for me.