Image Gallery Flashing a black screen before UIScrollview is visible - ios

Question

I am fetching an array of images that I have stored in PARSE and it all seems to be working fine, except that I am getting a blinking black flashing screen before the UIScrollView is visible. I believe that the black flash is this line:
[carousel setBackgroundColor:[UIColor blackColor]];
The background of the UIScrollView seems to be shown every time that I am loading a new image onto the carousel. I suspect that this is the cause of the blinking black screen.
NOTE This code is inside of a PFTableViewCell
Here is my code:
[PFObject fetchAllIfNeededInBackground:[gallery objectForKey:kFTPostPostsKey] block:^(NSArray *objects, NSError *error) {
if (!error) {
carousel = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 320.0f,320.0f)];
[carousel setUserInteractionEnabled:YES];
[carousel setDelaysContentTouches:YES];
[carousel setExclusiveTouch:YES];
[carousel setCanCancelContentTouches:YES];
[carousel setBackgroundColor:[UIColor blackColor]];
//add the scrollview to the view
carousel.pagingEnabled = YES;
[carousel setAlwaysBounceVertical:NO];
int i = 0;
for (PFObject *post in objects) {
PFFile *file = [post objectForKey:kFTPostImageKey];
[file getDataInBackgroundWithBlock:^(NSData *data, NSError *error) {
if (!error) {
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(didTapImageInGalleryAction:)];
singleTap.numberOfTapsRequired = 1;
CGFloat xOrigin = i * 320;
UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(xOrigin, 0, 320.0f, 320.0f)];
[imageView setBackgroundColor:[UIColor blackColor]];
UIImage *image = [UIImage imageWithData:data];
[imageView setImage:image];
[imageView setClipsToBounds:YES];
[imageView setContentMode:UIViewContentModeScaleAspectFill];
[imageView setUserInteractionEnabled:YES];
[imageView addGestureRecognizer:singleTap];
[carousel addSubview:imageView];
}
}];
i++;
}
[carousel setContentSize: CGSizeMake(320.0f * objects.count, 320.0f)];
[self.galleryButton addSubview:carousel];
[self.imageView setHidden:NO];
}
}];
My question is what is causing this blinking black screen? And how can I fix it?
Thanks!

Answer 1

I ended up moving this piece of code out of my the method which was being called often:
carousel = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 320.0f,320.0f)];
[carousel setUserInteractionEnabled:YES];
[carousel setDelaysContentTouches:YES];
[carousel setExclusiveTouch:YES];
[carousel setCanCancelContentTouches:YES];
[carousel setBackgroundColor:[UIColor blackColor]];
//add the scrollview to the view
carousel.pagingEnabled = YES;
[carousel setAlwaysBounceVertical:NO];
I moved that into the init and that did the trick for me. Now I just initialize the UIScrollView once and remove/add subviews when I need them refreshed.