How to reload only one cell in a collectionView?

Question

I have a collectionView and I have two problems. First, the scrolling is too laggy. My collectionView receives the data from an API in url and look like this:

This is my code:

extension ViewController: UICollectionViewDelegate, UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        if imageUrl.count >= 4 {
            activity.stopAnimating()
            activity.isHidden = true
        }else{
            DispatchQueue.main.async {
                self.myCollectionView.reloadData()
            }
        }

        return imageUrl.count
    }

    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = myCollectionView.dequeueReusableCell(withReuseIdentifier: "myViewCell", for: indexPath) as! myViewCell

        if let url = NSURL(string: imageUrl[indexPath.row]){
            if let data = NSData(contentsOf: url as URL){
                cell.carImageView.contentMode = UIViewContentMode.scaleAspectFit
                cell.carImageView.image = UIImage(data: data as Data)
            }
        }

        cell.firstLabel.text = firstLabelArray[indexPath.row]

        if secondLabelArray != []{
            cell.secondLabel.text = secondLabelArray[indexPath.row]
        }

        return cell
    }
}

The second problem that I have is I need refresh only the third cell in my collection view. That is my secondLabel but when I try with myCollectionView.reloadData() that reloads all of my cells. I need to refresh the third cell every second.

Answer 1

The problem with the lag in the collectionView can be the way tha you use NSData, consider use Alamofire Image, like this

if imageUrl.count > 0 {
        let eachImage = imageUrl[indexPath.row]
        Alamofire.request(eachImage).responseImage(completionHandler: {(response) in
            print("answer\(response)")
            if let image = response.result.value{
                DispatchQueue.main.async {
                    cell.ImageView.image = image
                }
            }
        })
        }

Answer 2

To load a particular cell use following:

let indexPath = IndexPath(item: 2, section: 0)
collectionView.reloadItems(at: [indexPath])

You are loading the image in cellForItemAt, Just ensure you are not loading an image on the main thread

You can use a library to download the image and cache an image

https://github.com/SDWebImage/SDWebImage

https://github.com/Alamofire/AlamofireImage