ios - Fade/dissolve when changing UIImageView's image

Question

Rather than creating two UIImageViews, it seems logical to simply change the image of one view. If I do that, is there anyway of having a fade/cross dissolve between the two images rather than an instant switch?

Answer 1

It can be much simpler using the new block-based, UIKit animation methods.

Suppose the following code is in the view controller, and the UIImageView you want to cross-dissolve is a subview of self.view addressable via the property self.imageView Then all you need is:

UIImage * toImage = [UIImage imageNamed:@"myname.png"];
[UIView transitionWithView:self.imageView
        duration:5.0f
        options:UIViewAnimationOptionTransitionCrossDissolve
        animations:^{
  self.imageView.image = toImage;
} completion:nil]

Done.

And to do it in Swift, it's like so:

let toImage = UIImage(named:"myname.png")
UIView.transitionWithView(self.imageView,
                          duration:5,
                          options: UIViewAnimationOptions.TransitionCrossDissolve, animations: { self.imageView.image = toImage }, completion: nil)

Swift 3, 4 & 5

let toImage = UIImage(named:"myname.png")
UIView.transition(with: self.imageView,
                  duration: 0.3,
                  options: .transitionCrossDissolve,
                  animations: { self.imageView.image = toImage },
                  completion: nil)