Center horizontal UICollectionView based on content - ios

Question

I have a horizontal UICollectionView which works fine. But I want to center cell when there is no need for scrolling. i.e.
if all cell are able to fit within the view width & user don't need to scroll then Do center the cell
if all cell are not able to fit within the view width & user need to scroll then Don't center the cell (default behaviour)
Graphical example:
UICollectionView that needs scrolling then keep default behavior
UICollectionView that doesn't need scrolling
What I have tried so far:
class ViewController: UIViewController, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
var dataList:[String] = ["icon_rotate", "icon_rotate2", "icon_rotate3", "icon_rotate4", "icon_rotate5", "icon_rotate6"]
override func viewDidLoad() {
super.viewDidLoad()
//other stuff
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
return (UIDevice.current.userInterfaceIdiom == .pad) ? 20.0 : 10.0
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
return (UIDevice.current.userInterfaceIdiom == .pad) ? 20.0 : 10.0
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: collectionView.frame.size.height * 0.75, height: collectionView.frame.size.height * 0.75)
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return dataList.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "editorCell", for: indexPath) as! EditorCell
cell.iconView.image = UIImage(named: dataList[indexPath.row])
return cell
}
}
This results in default behavior of UICollectionView so I searched in SO and found this post: How to center horizontally UICollectionView Cells?
and I added this code:
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAtIndex section: Int) -> UIEdgeInsets {
let totalCellWidth = CellWidth * CellCount
let totalSpacingWidth = CellSpacing * (CellCount - 1)
let leftInset = (collectionViewWidth - CGFloat(totalCellWidth + totalSpacingWidth)) / 2
let rightInset = leftInset
return UIEdgeInsets(top: 0, left: leftInset, bottom: 0, right: rightInset)
}
This code does work fine when there's few cells to be loaded but I want this to dynamically detect if centering is needed or let the default behavior stay in action.
Thanks

Answer 1

Assuming your current code is working when you the cells will fit - that is, it centers the "row of cells" when desired - change this line:
let leftInset = (collectionViewWidth - CGFloat(totalCellWidth + totalSpacingWidth)) / 2
to:
let leftInset = max(0, (collectionViewWidth - CGFloat(totalCellWidth + totalSpacingWidth)) / 2.0)
That way your insets will never be less than Zero