Why is this UITable Glitchy as I scroll?

Question

As I scroll throughout the tableView the images flicker in and out even though there is a cache implemented.

let imageCache = NSCache<NSString, UIImage>()

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Reuse", for: indexPath) as! TableViewCell

    if var downloadURL = URL(string: self.imageURLS[indexPath.row]) {
        //cell.cellImageView.contentMode = .scaleAspectFit
        // add constraints x,y, width and height

        if var image = imageCache.object(forKey: self.imageURLS[indexPath.row] as NSString) {
            cell.cellImageView.image = image
        } else {         
            URLSession.shared.dataTask(with: downloadURL!, completionHandler: {(data,response,error) in

                if error != nil {
                    print(error!)
                    return
                }
                let downloadedImage = UIImage(data:data!)
                self.imageCache.setObject(downloadedImage!, forKey: (downloadURL?.absoluteString as NSString?)!)
                DispatchQueue.main.async {
                    cell.cellImageView.image = downloadedImage
                    cell.cellImageView.image?.resizeImageWith()
                    tableView.beginUpdates()
                    tableView.endUpdates()
                }
            }).resume()
        }
        return cell
    }
    return cell
}

override func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    tableView.estimatedRowHeight = 500.0
    return UITableViewAutomaticDimension
}

Why are you setting the table view's `estimatedRowHeight` in the `heightForRowAt` method? Set that once (in `viewDidLoad`). Probably not related to your issue but you should fix that. — rmaddy, Jan 18 '18 at 04:41
@rmaddy Thank you for response, good catch, I have fixed it. Would you happen any solution for the glitches. — user372382, Jan 18 '18 at 04:47
Possible duplicate of https://stackoverflow.com/a/16663759/5471218 — dr_barto, Jan 18 '18 at 04:47
set `cell.cellImageView.image = nil` or in `prepareForReuse` — Lal Krishna, Jan 18 '18 at 05:15
@LalKrishna I have just tried that and it is still glitching — user372382, Jan 18 '18 at 05:21
Your whole else condition part should be on another thread I guess. — Sharad Chauhan, Jan 18 '18 at 05:55
@sharadchauhan I was told in another post that one should never download anything onto the main Queue — user372382, Jan 18 '18 at 08:43
@user372382 obviously not on main thread. https://stackoverflow.com/questions/24056205/how-to-use-background-thread-in-swift — Sharad Chauhan, Jan 18 '18 at 09:04
I think the issue is with the size of the image. May i know how large the image is? (KB or MB)? — Lal Krishna, Jan 20 '18 at 09:36

Why is this UITable Glitchy as I scroll?

0 Answers0