UICollectionViewCell 移动攻略

最近产品出了一个需要移动UICollectionViewCell需求，其中有点小挫折，与大家分享一下。

UICollectionView移动前提条件：

iOS版本必须大于iOS 9.0

Apple官方文档，关于UICollectionView移动方法如下：

    // Support for reordering
    @available(iOS 9.0, *)
    open func beginInteractiveMovementForItem(at indexPath: IndexPath) -> Bool // returns NO if reordering was prevented from beginning - otherwise YES

    @available(iOS 9.0, *)
    open func updateInteractiveMovementTargetPosition(_ targetPosition: CGPoint)

    @available(iOS 9.0, *)
    open func endInteractiveMovement()

    @available(iOS 9.0, *)
    open func cancelInteractiveMovement()

进入正文，给UICollectionView增加移动步骤如下

1. 给collectionView增加长按手势
2. 在手势识别中，设置各种移动事件
3. 在delegate设置对应cell是否可以移动
4. 在delegate中交换数据
5. 设置不可参与移动的IndexPath

具体代码如下：

import DKImagePickerController

class CommodityImageEditVC: UIViewController {
    // 选取图片框架
    var assets = [DKAsset]()
    
    let commodityImageEditCellID = "CommodityImageEditCellID"
    
    // 栏加载
    lazy var gridView: UICollectionView = {
        let flowLayout = UICollectionViewFlowLayout()
        flowLayout.itemSize = CGSize(width: 162.0, height: 162.0)
        flowLayout.sectionInset = UIEdgeInsets(top: 20, left: 50, bottom: 20, right: 50)
        flowLayout.minimumLineSpacing = 32.0
        
        let collectionView = UICollectionView(frame: CGRect.zero, collectionViewLayout: flowLayout)
        collectionView.backgroundColor = UIColor.white
        collectionView.register(CommodityImageEditCell.self, forCellWithReuseIdentifier: commodityImageEditCellID)
        collectionView.dataSource = self
        collectionView.delegate = self
        return collectionView;
    }()
    

    
    // MARK: - life cycle
    override func viewDidLoad() {
        super.viewDidLoad()

        setupView()
        
    }
    
    override func viewWillLayoutSubviews() {
        super.viewWillLayoutSubviews()
        // 设置表格视图大小
        gridView.frame = CGRect(x: 0, y: 0, width: view.width, height: view.height)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    // MARK: - setup view
    func setupView() {
        
        view.addSubview(gridView)
        
        setUpLongPressGesture()
    }
    
    /**
     给gridView增加长按事件
     */
    func setUpLongPressGesture() {
        let longPress = UILongPressGestureRecognizer(target: self, action: #selector(longPressMoving(longPress:)))
        gridView.addGestureRecognizer(longPress)
    }

}


// MARK: - 长按手势识别
extension CommodityImageEditVC {
    
    @objc func longPressMoving(longPress: UILongPressGestureRecognizer) {
        // 获取长按点
        let point = longPress.location(in: longPress.view)
        
        if #available(iOS 9, *) {
            switch longPress.state {
            case .began:
                // 根据长按点，获取对应cell的IndexPath
                guard let indexPath = gridView.indexPathForItem(at: point) else {
                    return
                }
                gridView.beginInteractiveMovementForItem(at: indexPath)
                
            case .changed:
                
                gridView.updateInteractiveMovementTargetPosition(point)
                
                
            case .ended:
                gridView.endInteractiveMovement()
            default:
                gridView.cancelInteractiveMovement()
            }
        }
    }
    
}

// MARK: - dataSource delegate
extension CommodityImageEditVC: UICollectionViewDataSource, UICollectionViewDelegate {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return assets.count + 1
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: commodityImageEditCellID, for: indexPath) as? CommodityImageEditCell
        if indexPath.row == assets.count {
            cell?.cellType = .add
        } else {
            cell?.cellType = .image
            cell?.updateCell(asset: assets[indexPath.row])
        }
        return cell!
    }
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        // 判断选中的是否为增加图片选项
        guard let cell = collectionView.cellForItem(at: indexPath) as? CommodityImageEditCell else {
            return
        }
        guard cell.cellType == .add else {
            return
        }
        let pickerController = DKImagePickerController()
        pickerController.didSelectAssets = {(assets: [DKAsset]) in
            self.assets.append(contentsOf: assets)
            self.gridView.reloadData()
        }
        present(pickerController, animated: true, completion: nil)
    }
    
    // 设置最后一个不可参与移动
    func collectionView(_ collectionView: UICollectionView, targetIndexPathForMoveFromItemAt originalIndexPath: IndexPath, toProposedIndexPath proposedIndexPath: IndexPath) -> IndexPath {
        if proposedIndexPath.item == assets.count {
            return originalIndexPath
        }
        if originalIndexPath.item == assets.count {
            return originalIndexPath
        }
        return proposedIndexPath
    }
    
    // 设置是否可以移动
    func collectionView(_ collectionView: UICollectionView, canMoveItemAt indexPath: IndexPath) -> Bool {
        if indexPath.row == assets.count {
            return false
        } else {
            return true
        }
        
    }
    
    func collectionView(_ collectionView: UICollectionView, moveItemAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
        // 移动后交换数据
        let moveData = assets.remove(at: sourceIndexPath.row)
        assets.insert(moveData, at: destinationIndexPath.row)
    }
}