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У меня есть CollectionView, где все мои ячейки выровнены по центру представления, используя пользовательский макет потока. Вот код для collectionViewController:

 let columnLayout = FlowLayout(
        minimumInteritemSpacing: 10,
        minimumLineSpacing: 10,
        sectionInset: UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
    )
    
    
    var dataSource: [String] = ["USA", "Brazil", "China","Really long long long", "Unite Kingdom", "Japan", "Mexico", "India",  "Really long long", "Short", "USA", "Brazil", "China","Really long long long", "Unite Kingdom", "Japan", "Mexico", "India",  "Really long long"]
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        
        
        collectionView.collectionViewLayout = columnLayout
        collectionView.contentInsetAdjustmentBehavior = .always
        collectionView.register(TestCell.self, forCellWithReuseIdentifier: "Cell")
        collectionView.dragInteractionEnabled = true
        collectionView.dragDelegate = self
        collectionView.dropDelegate = self
        collectionView.delegate = self
        collectionView.dataSource = self
    }
    
    
    
    
    override func numberOfSections(in collectionView: UICollectionView) -> Int {
        return 1
    }
    
    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return dataSource.count
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        // dataArary is the managing array for your UICollectionView.
        let item: String = dataSource[indexPath.row]
        return CGSize(width: item.widthOfString(usingFont: .systemFont(ofSize: 16))   25, height: 40)
    }
    
    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as? TestCell
        cell?.textLabel.text = dataSource[indexPath.row]
        return cell!
    }
    
    fileprivate func reorderItems(coordinator: UICollectionViewDropCoordinator, destinationIndexPath: IndexPath, collectionView: UICollectionView) {
        if let item = coordinator.items.first,
            let sourceIndexPath = item.sourceIndexPath {
            collectionView.performBatchUpdates ({
                self.dataSource.remove(at: sourceIndexPath.item)
                self.dataSource.insert(item.dragItem.localObject as! String, at: destinationIndexPath.item)
                
                collectionView.deleteItems(at: [sourceIndexPath])
                collectionView.insertItems(at: [destinationIndexPath])
                
            }, completion: nil)
            collectionView.reloadData()
            coordinator.drop(item.dragItem, toItemAt: destinationIndexPath)
            
        }
  

Код для класса FlowLayout:

 class FlowLayout: UICollectionViewFlowLayout {

    required init(minimumInteritemSpacing: CGFloat = 0, minimumLineSpacing: CGFloat = 0, sectionInset: UIEdgeInsets = .zero) {
        super.init()

        estimatedItemSize = UICollectionViewFlowLayout.automaticSize
        self.minimumInteritemSpacing = minimumInteritemSpacing
        self.minimumLineSpacing = minimumLineSpacing
        self.sectionInset = sectionInset
        sectionInsetReference = .fromSafeArea
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override func layoutAttributesForElements(in rect: CGRect) -> [UICollectionViewLayoutAttributes]? {
        let layoutAttributes = super.layoutAttributesForElements(in: rect)!.map { $0.copy() as! UICollectionViewLayoutAttributes }
        guard scrollDirection == .vertical else { return layoutAttributes }

        // Filter attributes to compute only cell attributes
        let cellAttributes = layoutAttributes.filter({ $0.representedElementCategory == .cell })

        // Group cell attributes by row (cells with same vertical center) and loop on those groups
        for (_, attributes) in Dictionary(grouping: cellAttributes, by: { ($0.center.y / 10).rounded(.up) * 10 }) {
            // Get the total width of the cells on the same row
            let cellsTotalWidth = attributes.reduce(CGFloat(0)) { (partialWidth, attribute) -> CGFloat in
                partialWidth   attribute.size.width
            }

            // Calculate the initial left inset
            let totalInset = collectionView!.safeAreaLayoutGuide.layoutFrame.width - cellsTotalWidth - sectionInset.left - sectionInset.right - minimumInteritemSpacing * CGFloat(attributes.count - 1)
            var leftInset = (totalInset / 2 * 10).rounded(.down) / 10   sectionInset.left

            // Loop on cells to adjust each cell's origin and prepare leftInset for the next cell
            for attribute in attributes {
                attribute.frame.origin.x = leftInset
                leftInset = attribute.frame.maxX   minimumInteritemSpacing
            }
        }

        return layoutAttributes
    }

}
  

Затем я добавил расширения UICollectionViewDragDelegate и UICollectionViewDropDelegate, чтобы позволить пользователю изменять порядок ячеек. Два расширения:

 extension CollectionViewController: UICollectionViewDragDelegate {
    func collectionView(_ collectionView: UICollectionView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {
        let item = self.dataSource[indexPath.row]
        let itemProvider = NSItemProvider(object: item as NSString)
        let dragItem = UIDragItem(itemProvider: itemProvider)
        dragItem.localObject = item
        return [dragItem]
    }
}

extension CollectionViewController: UICollectionViewDropDelegate {
    func collectionView(_ collectionView: UICollectionView, dropSessionDidUpdate session: UIDropSession, withDestinationIndexPath destinationIndexPath: IndexPath?) -> UICollectionViewDropProposal {
        if collectionView.hasActiveDrag {
            
            return UICollectionViewDropProposal(operation: .move, intent: .insertAtDestinationIndexPath)
            
        }
        
        return UICollectionViewDropProposal(operation: .forbidden)
    }
    
    func collectionView(_ collectionView: UICollectionView, performDropWith coordinator: UICollectionViewDropCoordinator) {
        var destinationindexPath: IndexPath
        if let indexPath = coordinator.destinationIndexPath {
            destinationindexPath = indexPath
        } else {
            let row = collectionView.numberOfItems(inSection: 0)
            destinationindexPath = IndexPath(item: row - 1, section: 0)
            
            
        }
        
        if coordinator.proposal.operation == .move {
            
            self.reorderItems(coordinator: coordinator, destinationIndexPath: destinationindexPath, collectionView: collectionView)
        }
    }
}
  

По какой-то странной причине ячейки отключаются в приложении при их изменении порядка:

https://imgur.com/dmEQLqh

Спасибо за помощь