Shadow rate on UITableViewCell contenview increasing while scrolling - ios

Question

In my app, I'm using dynamic height cells using auto layout. So for creating cardview effect I've to use tableview willdisplaycell method. It only add shadow only once to cell. But I don't know why shadow increasing while scrolling.
Here's my code
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
//setup card view style on cell
if !cellArray.contains(indexPath.row) {
cell.contentView.backgroundColor = UIColor.clear
let whiteRoundedView : UIView = UIView(frame: CGRect(x: 5.0, y: 5.0, width: cell.contentView.frame.size.width-10, height: cell.contentView.frame.size.height-10))
whiteRoundedView.layer.backgroundColor = UIColor.white.cgColor
whiteRoundedView.layer.masksToBounds = false
whiteRoundedView.layer.cornerRadius = 5.0
whiteRoundedView.layer.shadowOffset = CGSize(width: -1, height: 1)
whiteRoundedView.layer.shadowOpacity = 0.5
cell.contentView.addSubview(whiteRoundedView)
cell.contentView.sendSubview(toBack: whiteRoundedView)
cellArray.add(indexPath.row)
}
}

Answer 1

this piece of line is the causing the issue.
cell.contentView.addSubview(whiteRoundedView)
whenever willDisplayCell gets called, you will be adding the view everytime. That is the reason shadow is getting increased while scrolling. The solution is,
1. check the cell content view if the view is already added or not. If not, then add the view. use view tag to do it.
2. otherwise, create a shadow view and initialize the specific things in the -(void)awakeFromNib, which will get called only once.
but personally, i prefer option 2, which will isolate your view render logic from view controller or cell.
add the below code to your custom cell class. In this case, i have given leading-trialing-top-bottom constraints as 15-15-15-15. If you wish you can set it to 0. but make sure that it should in sync with the background constraints.
override func awakeFromNib() {
super.awakeFromNib()
contentView.backgroundColor = UIColor.clear
let whiteRoundedView : UIView = UIView(frame: CGRect(x: 5.0, y: 5.0, width: contentView.frame.size.width-10, height: contentView.frame.size.height-10))
whiteRoundedView.layer.backgroundColor = UIColor.white.cgColor
whiteRoundedView.layer.masksToBounds = false
whiteRoundedView.layer.cornerRadius = 5.0
whiteRoundedView.layer.shadowOffset = CGSize(width: -1, height: 1)
whiteRoundedView.layer.shadowOpacity = 0.5
whiteRoundedView.tag = shadowTag
whiteRoundedView.translatesAutoresizingMaskIntoConstraints=false
contentView.addSubview(whiteRoundedView)
contentView.sendSubview(toBack: whiteRoundedView)
let leading = NSLayoutConstraint(item: whiteRoundedView,
attribute: .leading,
relatedBy: .equal,
toItem: contentView,
attribute: .leading,
multiplier: 1.0,
constant: 15.0)
let trailing = NSLayoutConstraint(item: whiteRoundedView,
attribute: .trailing,
relatedBy: .equal,
toItem: contentView,
attribute: .trailing,
multiplier: 1.0,
constant: -15.0)
let top = NSLayoutConstraint(item: whiteRoundedView,
attribute: .top,
relatedBy: .equal,
toItem: contentView,
attribute: .top,
multiplier: 1.0,
constant: 15.0)
let bottom = NSLayoutConstraint(item: whiteRoundedView,
attribute: .bottom,
relatedBy: .equal,
toItem: contentView,
attribute: .bottom,
multiplier: 1.0,
constant: -15.0)
contentView.addConstraint(leading)
contentView.addConstraint(trailing)
contentView.addConstraint(top)
contentView.addConstraint(bottom)
}
Ref screenshot :

Answer 2

You can add your code here
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
var cell = tableView.dequeueReusableCell(withIdentifier: <idenitfier>, for: indexPath) as? JobListTableViewCell
if cell == nil {
//Initialization and setting of shadow
}
return cell
}
Hope this helps