Updating images in UIImageView during execution? - ios

Question

I have an interface which contains several UIImageView components on a view and i would like to update the animation images in run-time.
The main idea is to change the animation images into a thread with a delay of 2 seconds. The code below works fine. However, when i introduce a sleep time (with the commented NSThread sleepForTime); it no longer works. I am sure there is a logical explanation but i cannot identify it.
It's important to note that the animation is already running with another set of animated images.
Any help or tip is more than welcome :)
dispatch_async(allowToTouchThread, ^{
//[NSThread sleepForTimeInterval:2.0];
int randomnReward = 0;
WizzReward* currentReward = [rewardListForPages objectAtIndex:randomnReward];
WizzAnimalModel* animalModel = [gameLevelManager getAnimalModelByCategoryId: [currentReward getAnimalId]];
NSMutableArray* expressionsForAnimals = [animalModel getArrayForClosedEyesFaceExpression];
float animationDuration = [animalModel getStandardRewardAnimationDuration];
pageContentViewController.imagesArrayFileLevel1 = expressionsForAnimals;
pageContentViewController.animationLevel1Duration = animationDuration;
}
});

Answer 1

What about replacing your dispatch_async to a dispatch_after and set a delay of 2 seconds:
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
int randomnReward = 0;
WizzReward* currentReward = [rewardListForPages objectAtIndex:randomnReward];
WizzAnimalModel* animalModel = [gameLevelManager getAnimalModelByCategoryId: [currentReward getAnimalId]];
NSMutableArray* expressionsForAnimals = [animalModel getArrayForClosedEyesFaceExpression];
float animationDuration = [animalModel getStandardRewardAnimationDuration];
pageContentViewController.imagesArrayFileLevel1 = expressionsForAnimals;
pageContentViewController.animationLevel1Duration = animationDuration;
});

Answer 2

Changing the animated images without any timer, could be done directly by modifying the array of images.
However, changing the same animated images with a timer, needed 3 steps:
first the modification of the image arrays
second the actual re-association of the UIView AnimationImages to the modified array of images;
and finally startAnimating the UIView eventhough it hasn't been stopped beforehand
The source code below now works fine with a timer:
WizzReward* currentReward = [rewardListForPages objectAtIndex:0];
WizzAnimalModel* animalModel = [gameLevelManager getAnimalModelByCategoryId: [currentReward getAnimalId]];
NSMutableArray* expressionsForAnimals = [animalModel getArrayForClosedEyesFaceExpression];
pageContentViewController.imagesArrayFileLevel1 = expressionsForAnimals;
pageContentViewController.reward1CurrentPage.animationImages = pageContentViewController.imagesArrayFileLevel1;
[pageContentViewController.reward1CurrentPage startAnimating];
I did find neither "time vs no-timer difference"information in the literature nor actual reason why it should be done like that; but it works every time. Hope it helps anyone who runs into the same problem.