Swift 3 - UICollectionView Center Cell with Padding - ios

Question

I have a UICollectionView that scrolls horizontally and I would like to have one cell visible on the screen at a time.
I am programmatically setting the cell width and height in the following method:
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath as IndexPath) as! Cell
let width = collectionView.bounds.size.width - 40
let height = collectionView.bounds.size.height - 40
cell.bounds.size = CGSize(width: CGFloat(width), height: CGFloat(height))
return cell
}
And after struggling to figure out how to work with insets, spacing, section insets (both programmatically and in the inspectors in XCode) I can't seem to figure out what I need to set and where I need to set it.
Here is a diagram of my desired spacing:

Answer 1

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: IndexPath) -> CGSize {
return CGSize(width: UIScreen.main.bounds.width - 40, height: yourCollectionViewHeight - 40)
}
left 20 - add Footer Size and Header Size in storyboard with width = 20
spacing between cells - add Minimum Spacing in storyboard = 40
I could have made some mistakes and you will not get exactly your layout, but I hope you would get the idea.

Answer 2

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: collectionView.frame.width * 0.7, height: 300)
}
func collectionView(_ collectionView: UICollectionView, layoucollectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
let margin = collectionView.frame.width * 0.3
return UIEdgeInsets(top: 10, left: margin / 2, bottom: 10, right: margin / 2)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
return 0
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
return collectionView.frame.width * 0.3 / 2
}

Answer 3

If you want single cell visible on the screen at a time then important thing is that you should enable paging for your CollectionView. You can do it in swift as below :
collectionView.isPagingEnabled = true
Now conform your ViewController class to UICollectionViewDelegateFlowLayout and implement it's method sizeForItemAt indexPath which returns CGSize for your collectionview cell. For Example:
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 200, height: 200)
}