在两个UIButton图像之间淡入淡出

Question

我想在两个UIButton图像之间淡入淡出,以便在UITableView中设置收藏夹.

目前转换没有效果 - 它只是在点击/触摸时直接更改图像:

trans_img = [UIImage imageNamed:@"fav_on.png"];

NSArray *subviews = [owningCell subviews];
UIButton *favbutton = [subviews objectAtIndex:2];

favbutton.imageView.animationImages =
[NSArray arrayWithObjects:trans_img,
 nil];

[favbutton.imageView startAnimating];

我发现的一切都是UIViews之间的过渡:(

如果图像fav_off平滑地变成fav_on而另一种方式像fadein/fadeout那样圆形会很好.

Answer 1

看起来你正在寻找的就是这个.它可以动画UIButton上的图像,而无需添加新图像,创建数组或更改Alpha值!

CABasicAnimation *crossFade = [CABasicAnimation animationWithKeyPath:@"contents"];
crossFade.duration = 0.7;
crossFade.fromValue = (id)oldImage.CGImage;
crossFade.toValue = (id)newImage.CGImage;
crossFade.removedOnCompletion = NO;
crossFade.fillMode = kCAFillModeForwards;
[button.imageView.layer addAnimation:crossFade forKey:@"animateContents"];

//Make sure to add Image normally after so when the animation
//is done it is set to the new Image
[button setImage:newImage forState:UIControlStateNormal];

Answer 2

在swift中:

  import UIKit

   extension UIButton {

       func changeImageAnimated(image: UIImage?) {
           guard let imageView = self.imageView, currentImage = imageView.image, newImage = image else {
               return
           }
           let crossFade: CABasicAnimation = CABasicAnimation(keyPath: "contents")
           crossFade.duration = 0.3
           crossFade.fromValue = currentImage.CGImage
           crossFade.toValue = newImage.CGImage
           crossFade.removedOnCompletion = false
           crossFade.fillMode = kCAFillModeForwards
           imageView.layer.addAnimation(crossFade, forKey: "animateContents")
       }
   }


   self.playAndPauseVideo.changeImageAnimated(UIImage(named: "pauseVideo"))

Answer 3

感谢@jkanter的最佳答案.我把我变成了一个Swift 3.0扩展,我认为这对于偶然发现这篇文章的人来说也许有用.

extension UIButton {

    func setImage(_ image: UIImage?, for state: UIControlState, animated: Bool) {
        guard animated, let oldImage = imageView?.image, let newImage = image else {
            // Revert to default functionality
            setImage(image, for: state)
            return
        }

        let crossFade = CABasicAnimation(keyPath:"contents")
        crossFade.duration = 0.35
        crossFade.fromValue = oldImage.cgImage
        crossFade.toValue = newImage.cgImage
        crossFade.isRemovedOnCompletion = false
        imageView?.layer.add(crossFade, forKey: "animateContents")

        setImage(image, for: state)
    }
}

Answer 4

您可以尝试像这样转换 alpha 值以获得您想要的效果：

trans_img = [UIImage imageNamed:@"fav_on.png"];

NSArray *subviews = [owningCell subviews];
UIButton *favbutton = [subviews objectAtIndex:2];
[UIView animateWithDuration:0.5 animations:^{
    favbutton.alpha = 0.0f;
} completion:^(BOOL finished) {
    favbutton.imageView.animationImages = [NSArray arrayWithObjects:trans_img,nil];
    [favbutton.imageView startAnimating];
    [UIView animateWithDuration:0.5 animations:^{
        favbutton.alpha = 1.0f;
    }];
}];