UITableViewCell, images and aspect ratio

Question

I have a UITableView and I need to show different images (with different sizes) in each custom cell (with UIImageView). In order to display them properly I need to calculate aspect ratio of each image and adjust UIImageView's frame. But there is a problem. When I run the app, it displays wrong aspect ratio for every cell. Then I start sliding to the bottom of the table, and back to the top again, several times. And each time I see right aspect ratio, for some cells, and wrong for others. Is it because the system is reusing the prototype cell?

Here is the code in tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) :

func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCellWithIdentifier("EntryCell", forIndexPath: indexPath) as? PodCell

    let podcast = podList[indexPath.row]
    let title = podcast.title
    //        cell.titleLa?.text = title
    cell?.titleLabel.lineBreakMode = .ByWordWrapping
    cell?.titleLabel.numberOfLines = 0
    cell?.titleLabel.text = title
    var image = UIImage()
    if (imageCache[podcast.imageURL!] != nil) {
        image = imageCache[podcast.imageURL!]!
        cell?.imgView.image = image
    }else{
        let imgURL = NSURL(string: podcast.imageURL!)
        let request = NSURLRequest(URL: imgURL!)

        let config = NSURLSessionConfiguration.defaultSessionConfiguration()
        let session = NSURLSession(configuration: config)
        let task = session.dataTaskWithRequest(request) { (data: NSData?, response: NSURLResponse?,  error:NSError?) in
            if error == nil {
                if data != nil {
                    image = UIImage(data: data!)!
                }

                dispatch_async(dispatch_get_main_queue(), {
                    self.imageCache[podcast.imageURL!] = image
                    cell?.imgView.image = image
                })

            }else {
                print(error)
            }
        }

        task.resume()
    }
    let aspectRatio = image.size.width / image.size.height

    cell?.imgView.frame = CGRectMake((cell?.imgView.frame.origin.x)!, (cell?.imgView.frame.origin.y)!, (cell?.imgView.frame.width)!, (cell?.imgView.frame.width)! / aspectRatio)

    return cell!
}

Johannes Fahrenkrug Johannes Fahrenkrug · Accepted Answer · 2016-06-28T21:00:52

You can't use the imageView's frame's width as a basis for the new width. You need to use a constant value for that, maybe the height.

UITableViewCell, images and aspect ratio

2 Answers