CODEWITHSUNDEEP
iosobjective-cuicollectionviewuicollectionviewcell
Ian Zhao
Ian Zhao

Reputation: 1173

UICollectionViewCell disappears while scrolling

I'm using a uicollectionview to create a carousel like scroll view. I think the uicollectionview is the best approach with this use case. I was able to render uicollectionviewcell inside uicollectionview but the problems is, when I scroll the uicolectionview the later cells will disappear and all the cells went black in the end. Another issue is that the cell is not loaded until it's boundary is fully inside the Carousel.

this is how I set up my uicollectionviewcell inside cellForItemAtIndexPath delegate method

NSString *urlString = [NSString stringWithFormat:BASE_URL, panoid, heading, pitch];
NSURL *panoUrl = [NSURL URLWithString:urlString];

//WIDTH calculated based on screen size, roughly about three cells per screen.
CGFloat WIDTH = collectionView.frame.size.width / 3;

UIImageView *panoImg = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, WIDTH, 133.3)];
// add padding to imageview
panoImg.bounds = CGRectInset(panoImg.frame, 2, 2);
// do I need GCD to do async process here? the images are all loaded from urls. not sure if this will cause a problem.
dispatch_async(dispatch_get_global_queue(0, 0), ^{
    NSData *data = [NSData dataWithContentsOfURL:panoUrl];
    dispatch_async(dispatch_get_main_queue(), ^{
        [panoImg setImage:[UIImage imageWithData:data]];
    });
});
seeInsideCollectionViewCell *cell = [_panoCarousel dequeueReusableCellWithReuseIdentifier:@"panoCarouselCell" forIndexPath:indexPath];
cell.frame = CGRectMake(indexPath.item * WIDTH + 4, 0, WIDTH, 133.3);
cell.backgroundColor = [UIColor blackColor];
[cell addSubview: panoImg];

UILabel *label = [[UILabel alloc] initWithFrame: CGRectMake(4, 4, WIDTH, 15)];
[label setBackgroundColor: [UIColor colorWithRed:0.63 green:0.63 blue:0.63 alpha:0.5]];
[label setFont: [UIFont fontWithName:@"Roboto-Light" size:10.0]];
[label setText: _BussinessViewsNames[indexPath.item]];
[cell addSubview:label];

return cell;

any suggestions, the cells were all loaded, just the loading is not seamless and smooth, I've attached a gif to demonstrate the problem here.

enter image description here

Upvotes: 0

Views: 1255

Answers (1)

Misha Vyrko
Misha Vyrko

Reputation: 1000

remove this line due to you should not change frame for cell

cell.frame = CGRectMake(indexPath.item * WIDTH + 4, 0, WIDTH, 133.3);

When cell reusable, it already has uiimageview, and you again create new uiimageview and add it than cell will be has several uiimageviews as subview

Move load images in another class or method like

self.imageLoader

 -(void)loadImageWithURL:(NSURL *)url successBlock:(void (^)(UIImage *image, id itemId))successBlock failureBlock:(void (^)(NSError *error))failureBlock

and call it in cellForItem method (check id of gotten image)

Upvotes: 1

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