这里有一些不同的方法:UIAnimations，在我看来，这听起来像是你的挑战。

编辑:我太懒了:)

在这篇文章中，我提到了这个方法:

[newView setFrame:CGRectMake( 0.0f, 480.0f, 320.0f, 480.0f)]; //notice this is OFF screen!
[UIView beginAnimations:@"animateTableView" context:nil];
[UIView setAnimationDuration:0.4];
[newView setFrame:CGRectMake( 0.0f, 0.0f, 320.0f, 480.0f)]; //notice this is ON screen!
[UIView commitAnimations];

但是不是动画帧，而是动画alpha:

[newView setAlpha:0.0]; // set it to zero so it is all gone.
[UIView beginAnimations:@"animateTableView" context:nil];
[UIView setAnimationDuration:0.4];
[newView setAlpha:0.5]; //this will change the newView alpha from its previous zero value to 0.5f
[UIView commitAnimations];

[UIView transitionWithView:textFieldimageView
                  duration:0.2f
                   options:UIViewAnimationOptionTransitionCrossDissolve
                animations:^{
                    imageView.image = newImage;
                } completion:nil];

是另一种可能性

在iOS 5中，这就简单多了:

[newView setAlpha:0.0];
[UIView animateWithDuration:0.4 animations:^{
    [newView setAlpha:0.5];
}];

这太棒了

  self.imgViewPreview.transform = CGAffineTransform(scaleX: 0, y: 0)
          UIView.animate(withDuration: 1, delay: 0, usingSpringWithDamping: 0.3, initialSpringVelocity: 0, options: .curveEaseOut, animations: {
              self.imgViewPreview.image = newImage
              self.imgViewPreview.transform = .identity
          }, completion: nil)

为什么不试试这个呢?

NSArray *animationFrames = [NSArray arrayWithObjects:
  [UIImage imageWithName:@"image1.png"],
  [UIImage imageWithName:@"image2.png"], 
  nil];

UIImageView *animatedImageView = [[UIImageView alloc] init];
animatedImageView.animationImages = animationsFrame;
[animatedImageView setAnimationRepeatCount:1];
[animatedImageView startAnimating];

快速版本:

let animationsFrames = [UIImage(named: "image1.png"), UIImage(named: "image2.png")]
let animatedImageView = UIImageView()
animatedImageView.animationImages = animationsFrames
animatedImageView.animationRepeatCount = 1
animatedImageView.startAnimating()

代码:

var fadeAnim:CABasicAnimation = CABasicAnimation(keyPath: "contents");

fadeAnim.fromValue = firstImage;
fadeAnim.toValue   = secondImage;
fadeAnim.duration  = 0.8;         //smoothest value

imageView.layer.addAnimation(fadeAnim, forKey: "contents");

imageView.image = secondImage;

例子:

有趣，更详细的解决方案:(切换水龙头)

    let fadeAnim:CABasicAnimation = CABasicAnimation(keyPath: "contents");

    switch imageView.image {
        case firstImage?:
            fadeAnim.fromValue = firstImage;
            fadeAnim.toValue   = secondImage;
            imageView.image    = secondImage;
        default:
            fadeAnim.fromValue = secondImage;
            fadeAnim.toValue   = firstImage;
            imageView.image    = firstImage;
    }

    fadeAnim.duration = 0.8;

    imageView.layer.addAnimation(fadeAnim, forKey: "contents");