UICollectionView Cell Scroll to centre

Question

I am using UICollectionView in my UIViewController.

My collectionview properties are set as below.

Answer 1

Here's a Swift 3 version of @dmitry-zhukov (thanks btw!)

class PagedCollectionLayout : UICollectionViewFlowLayout {

    var previousOffset : CGFloat = 0
    var currentPage : CGFloat = 0

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {

        let sup = super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity)

        guard
            let validCollection = collectionView,
            let dataSource = validCollection.dataSource
            else { return sup }

        let itemsCount = dataSource.collectionView(validCollection, numberOfItemsInSection: 0)

        // Imitating paging behaviour
        // Check previous offset and scroll direction
        if  (previousOffset > validCollection.contentOffset.x) && (velocity.x < 0) {
            currentPage = max(currentPage - 1, 0)
        }
        else if (previousOffset < validCollection.contentOffset.x) && (velocity.x > 0) {
            currentPage = min(currentPage + 1, CGFloat(itemsCount - 1))
        }

        // Update offset by using item size + spacing
        let updatedOffset = ((itemSize.width + minimumInteritemSpacing) * currentPage)
        self.previousOffset = updatedOffset

        let updatedPoint = CGPoint(x: updatedOffset, y: proposedContentOffset.y)

        return updatedPoint
    }
}