两个UIButton图像之间的渐变

Question

我想在两个UIButton图像之间淡入，目的是在UITableView中设置收藏夹。

目前的过渡是没有效果的-它只是改变图像直接点击/触摸:

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uiview之间的过渡:(

如果图像fav_off顺利地变成fav_on，或者像fadein/fadeout一样变成fav_on，那就太好了。

Answer 1

看来你要找的是这个。它在不添加新图像，创建数组或改变alpha值的情况下，在UIButton上动画图像!

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

Here in swift:

  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的精彩回答。我把我的扩展做成了一个Swift 3.0扩展，我认为对任何偶然看到这篇文章的人来说也可能有用。

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

你可以试着像这样转换alpha值来得到你想要的效果:

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;
    }];
}];

Answer 5

这是对@Ponja的答案的一个轻微改进，通常效果很好。不幸的是，newImage不能"粘住"，所以如果你想在两个图像之间切换，第一个渐变会很顺利，但是回到原始图像会"快速"返回，没有渐变。通过使用cattransaction修复:

import UIKit
extension UIButton {
    func changeImageAnimated(image: UIImage?) {
        guard let imageView = self.imageView, currentImage = imageView.image, newImage = image else {
            return
        }
        CATransaction.begin()
        CATransaction.setCompletionBlock {
            self.setImage(newImage, forState: UIControlState.Normal)
        }
        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")
        CATransaction.commit()
    }
}

Answer 6

@SuperDuperTango的答案，添加了tintColor:

extension UIButton {
    func changeImageAnimated(image: UIImage?) {
        guard let imageView = self.imageView, currentImage = imageView.image, newImage = image else {
            return
        }
        CATransaction.begin()
        CATransaction.setCompletionBlock {
            self.setImage(newImage, forState: UIControlState.Normal)
        }
        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")
        CATransaction.commit()
        let crossFadeColor: CABasicAnimation = CABasicAnimation(keyPath: "contents")
        crossFadeColor.duration = 0.3
        crossFadeColor.fromValue = UIColor.blackColor()
        crossFadeColor.toValue = UIColor(red: 232.0/255.0, green: 85.0/255.0, blue: 71.0/255.0, alpha: 1.0)
        crossFadeColor.removedOnCompletion = false
        crossFadeColor.fillMode = kCAFillModeForwards
        imageView.layer.addAnimation(crossFadeColor, forKey: "animateContents")
        CATransaction.commit()
    }
}

Answer 7

@SuperDuperTango在Swift 4.2中的答案:

extension UIButton {
    func changeImageAnimated(image: UIImage?) {
        guard let imageView = self.imageView, let currentImage = imageView.image, let newImage = image else { return }
        CATransaction.begin()
        CATransaction.setCompletionBlock {
            self.setImage(newImage, for: .normal)
        }
        let crossFade: CABasicAnimation = CABasicAnimation(keyPath: "contents")
        crossFade.duration = 0.3
        crossFade.fromValue = currentImage.cgImage
        crossFade.toValue = newImage.cgImage
        crossFade.isRemovedOnCompletion = false
        crossFade.fillMode = CAMediaTimingFillMode.forwards
        imageView.layer.add(crossFade, forKey: "animateContents")
        CATransaction.commit()
    }
}

Answer 8

jkanter 答案迅速:

let crossFade = CABasicAnimation.init(keyPath: "contents")
crossFade.duration = 0.7
crossFade.fromValue = oldImage.cgImage
crossFade.toValue = newImage.cgImage
crossFade.isRemovedOnCompletion = false
crossFade.fillMode = kCAFillModeForwards
button.imageView?.layer.add(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, for: .normal)