How to load / show a UIImageView in cell after cell is populated

manpreet Best Answer 2 years ago

I have a UICollectionView of images, and in the corner of each cell i have a watermark (or a small icon). The images are fetched remotely and the icon is hardcoded (local). Everything is works fine except for one ugly problem: The local watermark icon is loading every cell first, while fetching the images, which is not a good look. ---> I'm looking for a way to load / show the watermark icon (UIImageView) after the each cell is populated (or worse case, after all cells are populated). Your help is always appreciated!

1. Is this possible? 2. Where would i implement it: cellForItemAt, viewDidLoad, etc.? 3. and then what would be the code. Please note i am relatively new to coding.

This is how i populate the collectionView with remotely store image (listeners not included):

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell
    {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "myproductCell", for: indexPath) as! MyProductsCollectionCell
        if (self.products.indices.contains(indexPath.row)) {
            let product = self.products[indexPath.row]
            cell.configureWithProduct(Product(caption: product.caption, videoUrl: product.videoUrl, imageUrl: product.imageUrl))

        }
        return cell
    }

And I've just created an outlet for the locally stored watermark (icon):

@IBOutlet weak var watermark: UIImageView!

manpreet 2 years ago

I haven't seen your code, so I can't comment. But definitely not in viewDidLoad.

You could use blocks to implement this in cellForItemAt.

- (__kindof UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    // download the image on the background thread
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        // once you have the image downloaded, 
        // set the image on a main thread
        // in the completion handler
        dispatch_async(dispatch_get_main_queue, ^{
            callback(yourImage); // this can be a call to your method.
        });
    });
}