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];

斯威夫特5:

当处理collectionView时。只加载一个项目或多个项目的动画。当改变单元格图像时，我尝试了一些不同的动画选项，没有区别，所以我没有在这里指明动画名称。

UIView.animate(withDuration: 1.0) { [weak self] in
                guard let self = self else { return print("gotchya!") }
                self.collectionView.reloadItems(at: [indexPath])
            }

[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];
}];

使用Swift 3

extension UIImageView{   
 var imageWithFade:UIImage?{
        get{
            return self.image
        }
        set{
            UIView.transition(with: self,
                              duration: 0.5, options: .transitionCrossDissolve, animations: {
                                self.image = newValue
            }, completion: nil)
        }
    }
}

用法:

myImageView.imageWithFade = myImage

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];