Swift+UIImageView: switch between two animation frame sequences? - swift

Question

Example of code for animation:
func startAnimation(index: Int) {
var jumpImages = ["Jump_1","Jump_2","Jump_3","Jump_4","Jump_5","Jump_6","Jump_7","Jump_8","Jump_9","Jump_10"]
if index == 1 {
jumpImages = ["Jump_11","Jump_21","Jump_31","Jump_41","Jump_51","Jump_61","Jump_71","Jump_81","Jump_91","Jump_101"]
}
var images = [UIImage]()
for image in jumpImages{
images.append(UIImage(named: image)!)
}
self.imageView.frame.origin.y = self.imageView.frame.origin.y + 100.0
self.imageView.animationImages = images
self.imageView.animationDuration = 2.0
self.imageView.animationRepeatCount = 1
self.imageView.startAnimating()
}
startAnimation(index: 0)
...
startAnimation(index: 1)
NOTE: Both startAnimation calls are in the main thread but not in the same run loop.
In my case I want to change jumpImages to another set of images. I should cancel the previous animation and start the new one but it looks like I set the last image in jumpImages sequence instead.
How to solve this issue?

Answer 1

Okay, I think I'm understanding your problem now -- from your statement, "[...] but it looks like I set the last image in jumpImages sequence instead," I think you mean that when you call startAnimation(index: 1), you are seeing just the last frame of the index 0 animations, and none of the index 1 animations.
Assuming that is right, your problem here going to be a race condition.
When you call startAnimation() then second time with index 1, the first animation may or may not still be in progress.
The solution will be to call self.imageView.stopAnimating() before you change all the images and start the new animation. The best practice would be to check the imageView.isAnimating flag before you call it. Something like this:
func startAnimation(index: Int) {
var jumpImages = ["Jump_1","Jump_2","Jump_3","Jump_4","Jump_5","Jump_6","Jump_7","Jump_8","Jump_9","Jump_10"]
if index == 1 {
jumpImages = ["Jump_11","Jump_21","Jump_31","Jump_41","Jump_51","Jump_61","Jump_71","Jump_81","Jump_91","Jump_101"]
}
var images = [UIImage]()
for image in jumpImages{
images.append(UIImage(named: image)!)
}
if self.imageView.isAnimating {
self.imageView.stopAnimating()
}
self.imageView.frame.origin.y = self.imageView.frame.origin.y + 100.0
self.imageView.animationImages = images
self.imageView.animationDuration = 2.0
self.imageView.animationRepeatCount = 1
self.imageView.startAnimating()
}
startAnimation(index: 0)
...
startAnimation(index: 1)
Also, since you're in a function and not within a closure, you can remove all those references to self., which makes things a bit shorter:
func startAnimation(index: Int) {
var jumpImages = ["Jump_1","Jump_2","Jump_3","Jump_4","Jump_5","Jump_6","Jump_7","Jump_8","Jump_9","Jump_10"]
if index == 1 {
jumpImages = ["Jump_11","Jump_21","Jump_31","Jump_41","Jump_51","Jump_61","Jump_71","Jump_81","Jump_91","Jump_101"]
}
var images = [UIImage]()
for image in jumpImages{
images.append(UIImage(named: image)!)
}
if imageView.isAnimating {
imageView.stopAnimating()
}
imageView.frame.origin.y = imageView.frame.origin.y + 100.0
imageView.animationImages = images
imageView.animationDuration = 2.0
imageView.animationRepeatCount = 1
imageView.startAnimating()
}
startAnimation(index: 0)
...
startAnimation(index: 1)