Add transition effect in a slideshow - xcode

Question

I'm trying to add a transition effect to my slideshow: here's my code
- (void)viewDidLoad
{
[super viewDidLoad];
photos = [[NSMutableArray alloc] init];
NSXMLParser *photoParser = [[NSXMLParser alloc] initWithContentsOfURL:[NSURL
URLWithString:#"http://localhost/index.xml"]];
[photoParser setDelegate:(id)self];
[photoParser parse];
currentImage = 0;
NSURL *imageURL = [NSURL URLWithString:[photos objectAtIndex:0]];
NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
[imgView setImage:[UIImage imageWithData:imageData]];
timer = [NSTimer scheduledTimerWithTimeInterval: 0.5
target: self
selector: #selector(handleTimer:)
userInfo: nil
repeats: YES];
}
- (void) handleTimer: (NSTimer *) timer {
currentImage++;
if ( currentImage >= photos.count )
currentImage = 0;
NSURL *imageURL = [NSURL URLWithString:[photos objectAtIndex:currentImage]];
NSData *imageData = [NSData dataWithContentsOfURL:imageURL];
[imgView setImage:[UIImage imageWithData:imageData]];
}
- (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName
namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName
attributes:(NSDictionary *)attributeDict {
if ( [elementName isEqualToString:#"photo"]) {
[photos addObject:[attributeDict objectForKey:#"url"]];
}
}
I think I should use
[UIView transitionFromView:currentView toView:nextView duration:1.0
options:UIViewAnimationOptionTransitionCrossDissolve completion:nil];
but I don't how to fill the transitionFRomView: and toView: fields. I only have one view
Thanks for your help

Answer 1

You can use the method transitionWithView:duration:options:animations:completion: for which the documentation says:
You can use this block to add, remove, show, or hide subviews of the specified view.
This is an example of how you can use that method:
- (void) handleTimer: (NSTimer *) timer {
currentImage++;
if (currentImage >= photos.count) currentImage = 0;
NSURL *imageURL = [NSURL URLWithString:[photos objectAtIndex:currentImage]];
NSData *imageData = [NSData dataWithContentsOfURL:imageURL]
[UIView transitionWithView:containerView
duration:2
options:UIViewAnimationOptionTransitionFlipFromLeft
animations:^{
[imgView removeFromSuperview];
imgView = // create a new image view
[imgView setImage:[UIImage imageWithData:imageData]];
[containerView addSubview:toView];
} completion:NULL];
}
Where containerView is the parent view of imgView and most likely is self.view.