iOS SDWebImage Cross Fade Effect UITableViewCell - ios

Question

This is how i am successfully using SDWebImageManager to download the images:
- (void) downloadThumbnails:(NSURL *) finalUrl
{
SDWebImageManager *manager = [SDWebImageManager sharedManager];
[manager downloadWithURL:finalUrl
options:0
progress:nil
completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished) {
if (image)
{
self.thumbnailURL = [finalUrl absoluteString];
}
}];
}
- (UIImage*)thumbnail {
if (!self.thumbnailURL) return nil;
return [[SDImageCache sharedImageCache] imageFromDiskCacheForKey:self.thumbnailURL];
}
How can i modify to have a cross fade effect? Cross Fade Effect is the one that makes the image showing transition slowly just like the TechCrunch iOS App. Thanks!
UPDATE: If i can do anything else to have cross fade effect (other than SDWebImage) in uitableview cell than you can write it in the answer.
UPDATE: I have received few answers after my last update and i am able to solve the problem partially. Using transitionWithView as in the answer below, it is working and cross fading the way i want BUT since i am using a tableivew controller that is loading more entries when it touches the bottom, it refreshes all the cells once before the new block of entries are loaded, how can i prevent this behaviour?

Answer 1

Looks like you are using the SDWebImageManager in a different file that is necessarily not the UITableViewController class. You can use transitionWithView but not with SDWebImageManager directly if its in a different class.
But in your table view controller class where you are using cellForRowAtIndexPath and linking the image with the imageView of UITableViewCell, you can using transitionView as below:
[UIView transitionWithView:cell.(Your Image View)
duration:0.5
options:UIViewAnimationOptionTransitionCrossDissolve
animations:^{
cell.(Your ImageView).image = [(how ever you are calling it)];
} completion:^(BOOL finished) {
// Optionally you can do anything after the completion
}];
Hope this helps!

Answer 2

You can use UIView transitionWithView:duration:options:animations:completion: method to cross dissolve image view from old image to the new one like this:
[UIView transitionWithView:imageView
duration:0.4
options:UIViewAnimationOptionTransitionCrossDissolve
animations:^{
// Set the new image
// Since its done in the animation block, the change will be animated
imageView.image = newImage;
} completion:^(BOOL finished) {
// Do whatever when the animation is finished
}];
Just use this code in your completed block where you would normally set the image to the imageView

Answer 3

please refer to the interface definition:
- (id<SDWebImageOperation>)downloadWithURL:(NSURL *)url
options:(SDWebImageOptions)options
progress:(SDWebImageDownloaderProgressBlock)progressBlock
completed:(SDWebImageCompletedWithFinishedBlock)completedBlock;
there are several value for SDImageOptions and I think this one is what you expected:
/**
* This flag enables progressive download, the image is displayed progressively during download as a browser would do.
* By default, the image is only displayed once completely downloaded.
*/
SDWebImageProgressiveDownload = 1 << 3