Snap to center of a cell when scrolling UICollectionView horizontally

by

While originally I was using Objective-C, I since switched so Swift and the original accepted answer did not suffice.

I ended up creating a UICollectionViewLayout subclass which provides the best (imo) experience as opposed to the other functions which alter content offset or something similar when the user has stopped scrolling.

class SnappingCollectionViewLayout: UICollectionViewFlowLayout {

    override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {
        guard let collectionView = collectionView else { return super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity) }

        var offsetAdjustment = CGFloat.greatestFiniteMagnitude
        let horizontalOffset = proposedContentOffset.x + collectionView.contentInset.left

        let targetRect = CGRect(x: proposedContentOffset.x, y: 0, width: collectionView.bounds.size.width, height: collectionView.bounds.size.height)

        let layoutAttributesArray = super.layoutAttributesForElements(in: targetRect)

        layoutAttributesArray?.forEach({ (layoutAttributes) in
            let itemOffset = layoutAttributes.frame.origin.x
            if fabsf(Float(itemOffset - horizontalOffset)) < fabsf(Float(offsetAdjustment)) {
                offsetAdjustment = itemOffset - horizontalOffset
            }
        })

        return CGPoint(x: proposedContentOffset.x + offsetAdjustment, y: proposedContentOffset.y)
    }
}

For the most native feeling deceleration with the current layout subclass, make sure to set the following:

collectionView?.decelerationRate = UIScrollViewDecelerationRateFast

More Related Contents:

  1. How to create a centered UICollectionView like in Spotify’s Player
  2. How can I make a UITextField move up when the keyboard is present – on starting to edit?
  3. Cell spacing in UICollectionView
  4. Left Align Cells in UICollectionView
  5. Creating a UICollectionView programmatically
  6. How to tap to zoom and double tap to zoom out in iOS?
  7. UIScrollView scroll to bottom programmatically
  8. Dynamic cell width of UICollectionView depending on label width
  9. Check if a UIScrollView reached the top or bottom
  10. ScrollView gesture recognizer eating all touch events
  11. UIScrollView: paging horizontally, scrolling vertically?
  12. Long press gesture on UICollectionViewCell
  13. Center content of UIScrollView when smaller
  14. View with continuous scroll; both horizontal and vertical
  15. UICollectionView Set number of columns
  16. automaticallyAdjustsScrollViewInsets not working
  17. UITableView inside UIScrollView not receiving first tap after scrollling
  18. What’s the UIScrollView contentInset property for?
  19. Programmatically scroll a UIScrollView
  20. Auto layout UIScrollView with subviews with dynamic heights
  21. Stop UIWebView from “bouncing” vertically?
  22. UICollectionView – didDeselectItemAtIndexPath not called if cell is selected
  23. Specifying one Dimension of Cells in UICollectionView using Auto Layout
  24. Dismissing the keyboard in a UIScrollView
  25. UICollectionView update a single cell
  26. UIRefreshControl with UICollectionView in iOS7
  27. Setting constraints programmatically
  28. Setting up UIScrollView to swipe between 3 view controllers
  29. UICollectionView current visible cell index
  30. Horizontal UIScrollView inside custom UITableViewCell – using IB Storyboard – Not scrolling

Leave a Comment