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问题:
I've been using SDWebImage on my iPhone app to handle all of the image loading. I am using a placeholder image, and I want to crossfade or fade in the new image once it loads. I am using a success block to set the image, and it is working great. No matter what I try, the image will not fade in though. I've tried sending the animation code back to the main thread, but that didn't help either. It just loads instantly... No animation.
Here is my code. Any thoughts?
// load placeholder image NSURL *url = ... _imageView = [[UIImageView alloc] init]; [_imageView setImage:[UIImage imageNamed:@"loading.jpg"]]; // request image SDWebImageManager *manager = [SDWebImageManager sharedManager]; [manager downloadWithURL:url delegate:self options:0 success:^(UIImage *image) { [UIView transitionWithView:_imageView duration:3.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{ [_imageView setImage:image]; } completion:NULL]; } failure:nil];
回答1:
You could set the imageView.alpha to 0 right before the animation block, then in the animation block have it animate back to imageView.alpha = 1.0;
// load placeholder image NSURL *url = ... _imageView = [[UIImageView alloc] init]; [_imageView setImage:[UIImage imageNamed:@"loading.jpg"]]; // request image SDWebImageManager *manager = [SDWebImageManager sharedManager]; [manager downloadWithURL:url delegate:self options:0 success:^(UIImage *image, BOOL cached) { imageView.alpha = 0.0; [UIView transitionWithView:_imageView duration:3.0 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{ [_imageView setImage:image]; imageView.alpha = 1.0; } completion:NULL]; } failure:nil];
回答2:
For SWIFT, i created this extension. It only fades in, when the image actually had to be downloaded from the web. If it was served from the cache, then it won't fade.
import UIKit import SDWebImage extension UIImageView { public func sd_setImageWithURLWithFade(url: NSURL!, placeholderImage placeholder: UIImage!) { self.sd_setImageWithURL(url, placeholderImage: placeholder) { (image, error, cacheType, url) -> Void in if let downLoadedImage = image { if cacheType == .None { self.alpha = 0 UIView.transitionWithView(self, duration: 0.2, options: UIViewAnimationOptions.TransitionCrossDissolve, animations: { () -> Void in self.image = downLoadedImage self.alpha = 1 }, completion: nil) } } else { self.image = placeholder } } } }
回答3:
SWIFT:
func setSDWebImageWithAnimation(imageViewToSet mImageView:UIImageView, URLToSet imageURL:NSURL!) { mImageView.image = UIImage(named: "favouritePlaceholder") SDWebImageManager.sharedManager().downloadImageWithURL(imageURL, options: nil, progress: nil) { (downloadedImage:UIImage!, error:NSError!, cacheType:SDImageCacheType, isDownloaded:Bool, withURL:NSURL!) -> Void in mImageView.alpha = 0 UIView.transitionWithView(mImageView, duration: 1.0, options: UIViewAnimationOptions.TransitionCrossDissolve, animations: { () -> Void in mImageView.image = downloadedImage mImageView.alpha = 1 }, completion: nil) } }
回答4:
This extension code worked better for me.
extension UIImageView { public func setImageWithFadeFromURL(url: NSURL, placeholderImage placeholder: UIImage? = nil, animationDuration: Double = 0.3) { self.sd_setImageWithURL(url, placeholderImage: placeholder) { (fetchedImage, error, cacheType, url) in if error != nil { print("Error loading Image from URL: \(url)\n(error?.localizedDescription)") } self.alpha = 0 self.image = fetchedImage UIView.transitionWithView(self, duration: (cacheType == .None ? animationDuration : 0), options: .TransitionCrossDissolve, animations: { () -> Void in self.alpha = 1 }, completion: nil) } } public func cancelImageLoad() { self.sd_cancelCurrentImageLoad() } }
回答5:
Try out this:
[self.myImage sd_setImageWithURL:storyThumbnailURL placeholderImage:[UIImage imageNamed:@"xyz"] completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) { if (cacheType == SDImageCacheTypeNone) { self.myImage.alpha = 0; [UIView animateWithDuration:0.3 animations:^{ self.myImage.alpha = 1; }]; } else { self.myImage.alpha = 1; } }];
回答6:
This is Swift 4 version of @Zoltan Varadi answer:
extension UIImageView { public func sd_setImageWithURLWithFade(url: URL!, placeholderImage placeholder: UIImage!) { self.sd_setImage(with: url, placeholderImage: placeholder) { (image, error, cacheType, url) -> Void in if let downLoadedImage = image { if cacheType == .none { self.alpha = 0 UIView.transition(with: self, duration: 0.3, options: UIViewAnimationOptions.transitionCrossDissolve, animations: { () -> Void in self.image = downLoadedImage self.alpha = 1 }, completion: nil) } } else { self.image = placeholder } } } }
I changed the duration to 0.3
You can add this function to the extension in order you need the completionHandler block:
public func sd_setImageWithURLWithFade(url: URL!, placeholderImage placeholder: UIImage!, comple: @escaping (Bool)->()) { self.sd_setImage(with: url, placeholderImage: placeholder, options: .allowInvalidSSLCertificates) { (image, error, cacheType, url) in if let downLoadedImage = image { if cacheType == .none { self.alpha = 0 UIView.transition(with: self, duration: 0.3, options: UIViewAnimationOptions.transitionCrossDissolve, animations: { () -> Void in self.image = downLoadedImage self.alpha = 1 }, completion: { _ in comple(true) }) } } else { self.image = placeholder } } }
