Swift 5扩展:

extension UIImageView{
    func setImage(_ image: UIImage?, animated: Bool = true) {
        let duration = animated ? 0.3 : 0.0
        UIView.transition(with: self, duration: duration, options: .transitionCrossDissolve, animations: {
            self.image = image
        }, completion: nil)
    }
}
 

用迈克尔·斯科特的话来说，傻瓜，保持简单。 以下是在Swift 3和Swift 4中实现这一点的简单方法:

UIView.transition(with: imageView,
                  duration: 0.75,
                  options: .transitionCrossDissolve,
                  animations: { self.imageView.image = toImage },
                  completion: nil)

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];

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)

我不确定你是否可以用渐隐效果动画UIViews，因为似乎所有支持的视图转换都在UIViewAnimationTransition枚举中定义。渐变效果可以使用CoreAnimation实现。该方法的示例示例:

#import <QuartzCore/QuartzCore.h>
...
imageView.image = [UIImage imageNamed:(i % 2) ? @"3.jpg" : @"4.jpg"];

CATransition *transition = [CATransition animation];
transition.duration = 1.0f;
transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
transition.type = kCATransitionFade;

[imageView.layer addAnimation:transition forKey:nil];

在iOS 5中，这就简单多了:

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