With AFNetworking, is very simple to download an image from a server and put into an UIImageView:
[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder-avatar"]];
How about if I want to do this replacement of image with an effect (maybe fade)???
It's because I want to make a slideshow with a lot of images.
UIImage contains the data for an image. UIImageView is a custom view meant to display the UIImage .
The first step is to drag the UIImageView onto your view. Then open the UIImageView properties pane and select the image asset (assuming you have some images in your project). You can also configure how the underlying image is scaled to fit inside the UIImageView.
You can use animateWithDuration
in conjunction with the rendition of setImageWithURL
that supplies the success
block, e.g.
[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder-avatar"] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) { self.imageView.alpha = 0.0; self.imageView.image = image; [UIView animateWithDuration:0.25 animations:^{ self.imageView.alpha = 1.0; }]; } failure:NULL];
Or, if you placeholder image isn't blank, you would probably want to cross dissolve via transitionWithView
:
[imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder-avatar"] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) { [UIView transitionWithView:self.imageView duration:0.3 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{ self.imageView.image = image; } completion:NULL]; } failure:NULL];
Update:
By the way, if you're concerned about the fact that the image view (and if you refer to self
, the view or the view controller, too) being retained until the download is done, you could:
__weak UIImageView *weakImageView = self.imageView; [imageView setImageWithURL:[NSURL URLWithString:@"http://i.imgur.com/r4uwx.jpg"] placeholderImage:[UIImage imageNamed:@"placeholder-avatar"] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) { UIImageView *strongImageView = weakImageView; // make local strong reference to protect against race conditions if (!strongImageView) return; [UIView transitionWithView:strongImageView duration:0.3 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{ strongImageView.image = image; } completion:NULL]; } failure:NULL];
Even if you do that, the image view is retained until the download completes, so you could optionally also cancel any download in progress in the dealloc
method of the view controller:
- (void)dealloc { // if MRC, call [super dealloc], too [_imageView cancelImageRequestOperation]; }
Try animating the alpha of the imageView from 0 to 1 when the online request completes with success:
// You should not call an ivar from a block (so get a weak reference to the imageView) __weak UIImageView *weakImageView = self.imageView; // The AFNetworking method to call [imageView setImageWithURLRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://host.com/image1.png"]] placeholderImage:nil] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image){ // Here you can animate the alpha of the imageview from 0.0 to 1.0 in 0.3 seconds [weakImageView setAlpha:0.0]; [UIView beginAnimations:nil context:NULL]; [UIView setAnimationDuration:0.3]; [weakImageView setAlpha:1.0]; [UIView commitAnimations]; } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error){ // Your failure handle code }
Of course you can use any other animation you like inside the completion block!
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