How to stop and center horizontal CollectionView Swift - ios

Question

I have a collection view that scrolls horizontally, but I cannot figure out how to make the cells center and stop at the center of each scroll. So for example if you swift left the next cell should be centered in the middle of the screen, how can I do this? I'll post the collection view I have created:
class TakesViewController: UICollectionViewController, UICollectionViewDelegateFlowLayout {
private lazy var selectionFeedbackGenerator = UISelectionFeedbackGenerator()
private let cellId = "TakeCell"
var currentActiveIndex: Int = 0
func setUpCollectionView(){
self.collectionView.isPrefetchingEnabled = true
self.collectionView.translatesAutoresizingMaskIntoConstraints = false
self.collectionView.backgroundColor = .clear
self.collectionView.showsHorizontalScrollIndicator = false
self.collectionView.showsVerticalScrollIndicator = false
self.collectionView.contentInset = UIEdgeInsets(top: 0, left: 15, bottom: 0, right: 15)
self.collectionView.alwaysBounceVertical = false
self.collectionView.alwaysBounceHorizontal = false
self.collectionView.decelerationRate = .fast
self.collectionView.configureForPeekingDelegate()
self.collectionView.register(UINib(nibName: "TakesCollectionViewCell", bundle: nil), forCellWithReuseIdentifier: "TakeCell")
}
init() {
let flowLayout = UICollectionViewFlowLayout()
flowLayout.scrollDirection = .horizontal
flowLayout.minimumLineSpacing = 15
super.init(collectionViewLayout: flowLayout)
}
required init?(coder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
override func viewDidLoad() {
super.viewDidLoad()
collectionView.delegate = self
collectionView.dataSource = self
setUpCollectionView()
}
}
extension TakesViewController {
override func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return 12
}
override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: self.cellId, for: indexPath) as? TakeCollectionViewCell else {return UICollectionViewCell()}
return cell
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
return CGSize(width: 320, height: 575)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
//Where elements_count is the count of all your items in that
//Collection view...
let cellCount = CGFloat(12)
//If the cell count is zero, there is no point in calculating anything.
if cellCount > 0 {
let flowLayout = collectionViewLayout as! UICollectionViewFlowLayout
let cellWidth = flowLayout.itemSize.width + flowLayout.minimumInteritemSpacing
//20.00 was just extra spacing I wanted to add to my cell.
let totalCellWidth = cellWidth*cellCount + 20.00 * (cellCount-1)
let contentWidth = collectionView.frame.size.width - collectionView.contentInset.left - collectionView.contentInset.right
if (totalCellWidth < contentWidth) {
//If the number of cells that exists take up less room than the
//collection view width... then there is an actual point to centering them.
//Calculate the right amount of padding to center the cells.
let padding = (contentWidth - totalCellWidth) / 2.0
return UIEdgeInsets(top: 0, left: padding, bottom: 0, right: padding)
} else {
//Pretty much if the number of cells that exist take up
//more room than the actual collectionView width, there is no
// point in trying to center them. So we leave the default behavior.
return UIEdgeInsets(top: 0, left: 40, bottom: 0, right: 40)
}
}
return UIEdgeInsets.zero
}
}

Answer 1

It's a scroll view. Where it stops when the user lets go is up to you.
https://developer.apple.com/documentation/uikit/uiscrollviewdelegate/1619385-scrollviewwillenddragging