dsk1306

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    let pageWidth = <#page width#>
    let collectionViewContentWidth = collectionView.contentSize.width

    if velocity.x == 0 {
        page = Int(floor((targetContentOffset.pointee.x - pageWidth / 2) / pageWidth) + 1.0)
    } else {
        page = velocity.x > 0 ? page + 1 : page - 1
        if page < 0 {
            page = 0