Collection view auto-scrolling on gesture based rearrangement

Question

I have an app where photos gets listed in the collection view in multiple sections, got the feature request to add the rearrangement so I added the gesture based rearrangement to collection view.

Issue: after a bit of rearrangement, it got to a stage where the collection view automatically got scrolled to the bottom of the screen. If I try to scroll back up, it got scrolled back automatically to bottom of the screen.

Any help would be greatly appreciated.

Stack trace

#0  0x00000001274dc952 in -[UIScrollView setContentOffset:] ()
#1  0x0000000126614327 in -[UICollectionView setContentOffset:] ()
#2  0x00000001274ff1d3 in -[UIScrollView _setContentOffset:animated:animationCurve:animationAdjustsForContentOffsetDelta:animation:animationConfigurator:] ()
#3  0x00000001274fee62 in -[UIScrollView _setContentOffset:animated:animationCurve:animationAdjustsForContentOffsetDelta:animation:] ()
#4  0x000000012661429f in -[UICollectionView setContentOffset:animated:] ()
#5  0x0000000126634c2c in -[UICollectionView _autoScrollAssistantUpdateContentOffset:] ()
#6  0x00000001273eebd1 in -[_UIAutoScrollAssistant _handleAutoScrollerWithContentOffset:direction:] ()
#7  0x00000001273eeb0c in -[_UIAutoScrollAssistant displayLinkFired:] ()
#8  0x0000000113d250ec in CA::Display::DisplayLink::dispatch_items(unsigned long long, unsigned long long, unsigned long long) ()
#9  0x0000000113e1d435 in display_timer_callback(__CFMachPort*, void*, long, void*) ()
#10 0x000000011520075d in __CFMachPortPerform ()
#11 0x00000001152346e1 in __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ ()
#12 0x0000000115233aae in __CFRunLoopDoSource1 ()
#13 0x000000011522dfe8 in __CFRunLoopRun ()
#14 0x000000011522d0f3 in CFRunLoopRunSpecific ()
#15 0x000000011aee3cd3 in GSEventRunModal ()
#16 0x0000000126fb4f42 in -[UIApplication _run] ()
#17 0x0000000126fb9b5e in UIApplicationMain ()

Here is the code

CollectionView

lazy var collectionView: UICollectionView = {
    let layout = UICollectionViewFlowLayout()
    layout.scrollDirection = .vertical
    let collectionView = UICollectionView(frame: .zero, collectionViewLayout: layout)
    collectionView.bounces = false
    collectionView.backgroundColor = .white
    collectionView.delegate = self
    collectionView.dataSource = self
    collectionView.register(CustomCell.self, forCellWithReuseIdentifier: reuseIden)
    collectionView.contentInset = .init(top: 18, left: 0, bottom: 18, right: 0)
    return collectionView
}()

Gesture recognizer

private func addGestureRecognizer() {
    let longPressGesture = UILongPressGestureRecognizer(target: self, action: #selector(self.handleLongGesture(gesture:)))
    longPressGesture.minimumPressDuration = 0.5
    longPressGesture.allowableMovement = 1
    collectionView.addGestureRecognizer(longPressGesture)
  }


@objc func handleLongGesture(gesture: UILongPressGestureRecognizer) {
    switch(gesture.state) {
    case .began:
      guard let selectedIndexPath = collectionView.indexPathForItem(at: gesture.location(in: collectionView)) else {
        break
      }
      
      collectionView.beginInteractiveMovementForItem(at: selectedIndexPath)
      
    case .changed:
      collectionView.updateInteractiveMovementTargetPosition(gesture.location(in: collectionView))
      
    case .ended:
      collectionView.endInteractiveMovement()
      
    default:
      collectionView.cancelInteractiveMovement()
      
    }
  }

Move item

extension CollectionViewController {
  func collectionView(_ collectionView: UICollectionView, canMoveItemAt indexPath: IndexPath) -> Bool {
    return true
  }
  
  func collectionView(_ collectionView: UICollectionView, moveItemAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
    collectionView.performBatchUpdates({
      let row = sections[sourceIndexPath.section].rows.remove(at: sourceIndexPath.item)
      sections[destinationIndexPath.section].rows.insert(row, at: destinationIndexPath.item)

    }, completion: { _ in

      DispatchQueue.main.async {
        self.collectionView.reloadData()
      }
      
    })
    
  }
  
  func collectionView(_ collectionView: UICollectionView, targetIndexPathForMoveFromItemAt originalIndexPath: IndexPath, toProposedIndexPath proposedIndexPath: IndexPath) -> IndexPath {
    return proposedIndexPath
  }
  
}

Data source and delegates

extension CollectionViewController:
  UICollectionViewDataSource,
  UICollectionViewDelegate,
  UICollectionViewDelegateFlowLayout {
  
  func collectionView(_ collectionView: UICollectionView,
                      numberOfItemsInSection section: Int) -> Int { sections[section].rows.count }
  
  func numberOfSections(in collectionView: UICollectionView) -> Int { sections.count }
  
  func collectionView(_ collectionView: UICollectionView,
                      cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIden, for: indexPath) as! CustomCell
    return cell
  }
  
  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      minimumLineSpacingForSectionAt section: Int) -> CGFloat { StandardPadding }
  
  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      minimumInteritemSpacingForSectionAt section: Int) -> CGFloat { StandardPadding }
  
  func collectionView(_ collectionView: UICollectionView,
                      layout collectionViewLayout: UICollectionViewLayout,
                      sizeForItemAt indexPath: IndexPath) -> CGSize {
    let collectionWidth = collectionView.frame.width
    let itemWidth = (collectionWidth/2)-StandardPadding*1.5
    return .init(width: itemWidth, height: (itemWidth*IMAGERATIO))
  }
  
  func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
    return .init(top: StandardPadding, left: StandardPadding, bottom: StandardPadding, right: StandardPadding)
  }
  
}