swift – Collectionview交互式单元交换

class ViewController: UIViewController,UICollectionViewDatasource {

    var arr: [String] = (0...100).map { return "\($0)" }

    lazy var collectionView: UICollectionView =  {
        let layout = UICollectionViewFlowLayout()
        let cv: UICollectionView = UICollectionView(frame: self.view.bounds,collectionViewLayout: layout)
        cv.register(Cell.self,forCellWithReusEIDentifier: Cell.id)
        layout.itemSize = CGSize(width: view.bounds.width/3.5,height: 100)
        cv.datasource = self
        cv.addGestureRecognizer(longPressGesturE)
        return cv
    }()

    lazy var longPressGesture: UILongPressGestureRecognizer = UILongPressGestureRecognizer(target: self,action: #SELEctor(self.handleLongGesture(gesture:)))

    private var movingCell: MovingCell?

    override func viewDidLoad() {
        super.viewDidLoad()
        view = collectionView
    }

    @objc func handleLongGesture(gesture: UILongPressGestureRecognizer) {

        var cell: (UICollectionViewCell?,IndexPath?) {
            guard let indexPath = collectionView.indexPathForItem(at: gesture.LOCATIOn(in: collectionView)),let cell = collectionView.cellForItem(at: indexPath) else { return (nil,nil) }
            return (cell,indexPath)
        }

        switch(gesture.statE) {

        case .began:
            movingCell = MovingCell(cell: cell.0,originalLOCATIOn: cell.0?.center,indexPath: cell.1)
            break
        case .changed:

            /// Make sure moving cell floats above its siblings.
            movingCell?.cell.layer.zPosition = 100
            movingCell?.cell.center = gesture.LOCATIOn(in: gesture.view!)

            break
        case .ended:

            swapMovingCellWith(cell: cell.0,at: cell.1)
            movingCell = nil
        default:
            movingCell?.reset()
            movingCell = nil
        }
    }

    func swapMovingCellWith(cell: UICollectionViewCell?,at indexPath: IndexPath?) {
        guard let cell = cell,let moving = movingCell else {
            movingCell?.reset()
            return
        }

        // update data source
        arr.swapAt(moving.indexPath.row,indexPath!.row)

        // swap cells
        animate(moving: moving.cell,to: cell)
    }

    func animate(moving movingCell: UICollectionViewCell,to cell: UICollectionViewCell) {
        longPressGesture.isEnabled = false

        UIView.animate(withDuration: 0.4,delay: 0,usingSpringWithDamping: 0.1,initialSpringVeLocity: 0.7,options: UIViewAnimationOptions.allowUserInteraction,animations: {
            movingCell.center = cell.center
            cell.center = movingCell.center
        }) { _ in
            self.collectionView.reloadData()
            self.longPressGesture.isEnabled = true
        }
    }

    func collectionView(_ collectionView: UICollectionView,numberOfItemsInSection section: int) -> Int {
        return arr.count
    }

    func collectionView(_ collectionView: UICollectionView,cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell: Cell = collectionView.dequeueReusableCell(withReusEIDentifier: Cell.id,for: indexPath) as! Cell
        cell.titleLable.text = arr[indexPath.row]
        return cell
    }

    private struct MovingCell {
        let cell: UICollectionViewCell
        let originalLOCATIOn: CGPoint
        let indexPath: IndexPath

        init?(cell: UICollectionViewCell?,originalLOCATIOn: CGPoint?,indexPath: IndexPath?) {
            guard cell != nil,originalLOCATIOn != nil,indexPath != nil else { return nil }
            self.cell = cell!
            self.originalLOCATIOn = originalLOCATIOn!
            self.indexPath = indexPath!
        }

        func reset() {
            cell.center = originalLOCATIOn
        }
    }

    final class Cell: UICollectionViewCell {
        static let id: String = "CellId"

        lazy var titleLable: UILabel = UILabel(frame: CGRect(x: 0,y: 20,width: self.bounds.width,height: 30))

        override init(frame: CGRect) {
            super.init(frame: framE)
            addSubview(titleLablE)
            titleLable.BACkgroundColor = .green
            BACkgroundColor = .white
        }

        required init?(coder aDecoder: NSCoder) {
            super.init(coder: aDecoder)
        }
    }
}