UIView transitionWithView never transitions to another photo - ios

Question

I am trying to do a slide show like animation on the home page of my app. An image appears in the proper UI View, but it never transitions to a different photo.
EDIT: Trying to set the image before transition view:
- (void)viewDidLoad {
[super viewDidLoad];
/*set image before transition */
_slideShow.image = [UIImage imageNamed:#"Slide Show"];
[self fetchSpecies];
[self beginSlideShow];
}
- (void) beginSlideShow{
NSLog(#"Called");
if([imageUrls_ count] < 1){
NSLog(#"EMPTY");
return;
}
[UIView transitionWithView:_slideShow duration:0.2 options: UIViewAnimationOptionTransitionCrossDissolve animations:^{
int index = arc4random() % [imageUrls_ count];
_slideShow.image = [self getImage:index];
// Account for the case where some images just aren't there
while (_slideShow.image == nil) {
index = arc4random() % [imageUrls_ count];
_slideShow.image = [self getImage:index];
}
} completion:^(BOOL finished) {
if (finished){
//logic
}
}];
}
- (void) fetchSpecies{
NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:# "Species"];
NSError* error = nil;
NSManagedObjectContext* context = [(LeafletAppDelegate*)[[UIApplication sharedApplication] delegate] managedObjectContext];
NSArray* species = [context executeFetchRequest:request error:&error];
if (!species || error) { // nil is an error
NSLog(#"error");
// handle error
}
// Get all the image urls and description to use for the random images
imageUrls_ = [[NSMutableArray arrayWithCapacity:100] retain];
imageDescs_ = [[NSMutableArray arrayWithCapacity:100] retain];
NSString *url;
NSString *name;
for (Species *s in species) {
name = [NSString stringWithFormat:#"%#", [s commonNameFirstLast]];
url = [s.ExampleImageLeaf pathForLocalImageUsingThumbnail:YES];
if (url) {
[imageUrls_ addObject:url];
[imageDescs_ addObject:[NSString stringWithFormat:#"%#", name]];
}
url = [s.ExampleImageFlower pathForLocalImageUsingThumbnail:YES];
if (url) {
[imageUrls_ addObject:url];
[imageDescs_ addObject:[NSString stringWithFormat:#"%#", name]];
}
url = [s.ExampleImageFruit pathForLocalImageUsingThumbnail:YES];
if (url) {
[imageUrls_ addObject:url];
[imageDescs_ addObject:[NSString stringWithFormat:#"%#", name]];
}
}
}
- (UIImage *) getImage:(NSUInteger)index
{
// NSLog(#"empty");
NSString *url = [imageUrls_ objectAtIndex:index];
return [UIImage imageWithContentsOfFile:url];
}
I checked and imageUrls has 660 elements, so its not an issue of not having enough photos. I would be very grateful for any insight/suggestions, I am very new to iOS.

Answer 1

I have taken two images for demo purpose, and i have changed the view's tag on swipe action to change the image based on tag value. The imageView transitions from one photo to another. Below the code is given where slideView is an UIImageView.
Swift3
Inside viewDidLoad method:
slideView.image = UIImage(named: "image1")
slideView.tag = 0
On Swipe action called the below method:
func beginSlideShow() {
UIView.transition(with: slideView, duration: 1.0, options: [.transitionCrossDissolve, .curveEaseOut], animations: {
if self.slideView.tag == 1 {
self.slideView.image = UIImage(named: "image2")
} else {
self.slideView.image = UIImage(named: "image1")
}
}, completion: { (finished: Bool) in
if finished {
NSLog("animation finished")
}
})
}
Objective-C
- (void) beginSlideShow {
[UIView transitionWithView:_slideView duration:1.0 options: UIViewAnimationOptionTransitionCrossDissolve animations:^{
if (_slideView.tag == 1) {
_slideView.image = [UIImage imageNamed:#"image2"];
} else {
_slideView.image = [UIImage imageNamed:#"image1"];
}
} completion:^(BOOL finished) {
if (finished) {
NSLog(#"animation finished");
}
}];
}