原理

为UITableView添加一个长按手势，然后给选中的 cell截图；让截图随着手势移动，同时记录选中的indexPath，方便位置互换。

IDL 为 iOSDevLog 简写

定义接口

定义接口 IDLMoveableCellTableViewDataSource

@objc protocol IDLMoveableCellTableViewDataSource  {
    // original datasource
    func dataSourceArray(in tableView: UITableView) -> [Any]
    
    // exchanged datasource
    func tableView(_ tableView: UITableView, newDataSourceArrayAfterMove newDataSourceArray: [Any])
}

定义接口 IDLMoveableCellTableViewDelegate

@objc protocol IDLMoveableCellTableViewDelegate {
    func tableView(_ tableView: UITableView, willMoveCellAt indexPath: IndexPath)
    func tableView(_ tableView: UITableView, didMoveCellFrom fromIndexPath: IndexPath, to toIndexPath: IndexPath)
    func tableView(_ tableView: UITableView, endMoveCellAt indexPath: IndexPath)
    func tableView(_ tableView: UITableView, drawMovealbeCell: UIView)
}

扩展 UITableView

@IBDesignable extension UITableView { }

@IBInspectable

用 @IBInspectable 修饰的属性会显示在 IB 的 Show the Attributes inspector。

extension UIView {
    private struct AssociatedKeys {
        static var name: String?
    }
    
    // 存储属性
    @IBInspectable var name: String {
        get {
            return objc_getAssociatedObject(self, &AssociatedKeys.name) as! String
        }
        set {
            objc_setAssociatedObject(self, &AssociatedKeys.name, newValue, .OBJC_ASSOCIATION_RETAIN)
        }
    }
    
    
    // 计算属性
    @IBInspectable var borderColor: UIColor {
        set {
            self.layer.borderColor = newValue.cgColor
        }
        get {
            return UIColor.init(cgColor: self.layer.borderColor!)
        }
    }
}

在struct中定义常量

    private struct IDLConstraint {
        static let kIDLMoveableCellAnimationTime: TimeInterval = 0.25
        static let kIDLMinimumPressDuration: CFTimeInterval = 0.2
    }
    
    private struct IDLAssociatedKeys {
        static var iDLDataSourceName: String?
        static var iDLMoveableDelegateName: String?
        static var iDLGestureMinimumPressDurationName: String?
        static var iDLGestureName: String?
        static var iDLTempViewName: String?
        static var iDLEdgeScrollTimerName: String?
        static var iDLSelectedIndexPathName: String?
        static var iDLEdgeScrollRangeName: String?
        static var iDLIsCanEdgeScrollName: String?
        static var iDLMoveableDataSourceName: String?
        static var iDLDrawMovalbeCellBlockName: String?
    }

定义 IBOutlet 和 IBInspectable

    // MARK: - outlet
    @IBOutlet var moveableDataSource: IDLMoveableCellTableViewDataSource?  
    @IBOutlet var  moveableDelegate: IDLMoveableCellTableViewDelegate? 
    
    // MARK: - inspectable
    // trigger moveable long press duration
    @IBInspectable var gestureMinimumPressDuration: CFTimeInterval  
    // edge scroll enable
    @IBInspectable var isCanEdgeScroll: Bool 
    // edge scroll distance
    @IBInspectable var edgeScrollRange: CGFloat 

添加长按手势

    private func iDLAddGesture() {
        _iDLGesture = UILongPressGestureRecognizer(target: self, action: #selector(self.iDLProcessGesture))
        _iDLGesture?.minimumPressDuration = CFTimeInterval(gestureMinimumPressDuration)
        addGestureRecognizer(_iDLGesture!)
    }
    
    @objc
    private func iDLProcessGesture(_ gesture: UILongPressGestureRecognizer) {
        switch gesture.state {
        case .began:
            iDLGestureBegan(gesture)
        case .changed:
            if !isCanEdgeScroll {
                iDLGestureChanged(gesture)
            }
        case .ended, .cancelled:
            iDLGestureEndedOrCancelled(gesture)
        default:
            break
        }
    }

手势具体操作

    // remember selectedIndex and snapshot selected cell
    private func iDLGestureBegan(_ gesture: UILongPressGestureRecognizer) {}
    // update snapshot
    private func iDLGestureChanged(_ gesture: UILongPressGestureRecognizer) {
        ...
        iDLUpdateDataSourceAndCell(from: self._iDLSelectedIndexPath!, to: currentIndexPath!)
        ...
    }
    // update datasource and remove snapshot
    private func iDLGestureEndedOrCancelled(_ gesture: UILongPressGestureRecognizer) { }

交换 cell

    private func iDLUpdateDataSourceAndCell(from fromIndexPath: IndexPath, to toIndexPath: IndexPath) {
        if numberOfSections == 1 {
            // only 1 section
            let fromData = self._iDLMoveableDataSource[fromIndexPath.row]
            let toData = self._iDLMoveableDataSource[toIndexPath.row]
            self._iDLMoveableDataSource[fromIndexPath.row]  = toData
            self._iDLMoveableDataSource[toIndexPath.row] = fromData
            beginUpdates()
            moveRow(at: fromIndexPath, to: toIndexPath)
            moveRow(at: toIndexPath, to: fromIndexPath)
            endUpdates()
        } else if (fromIndexPath.section == toIndexPath.section) {
            // same section
            var changeArray = _iDLMoveableDataSource[fromIndexPath.section] as! [Any]
            let fromData = changeArray[fromIndexPath.row]
            let toData = changeArray[toIndexPath.row]
            changeArray[toIndexPath.row] = fromData
            changeArray[fromIndexPath.row] = toData
            _iDLMoveableDataSource[fromIndexPath.section] = changeArray
            
            beginUpdates()
            moveRow(at: fromIndexPath, to: toIndexPath)
            moveRow(at: toIndexPath, to: fromIndexPath)
            endUpdates()
        } else {
            // different section
            var fromArray = _iDLMoveableDataSource[fromIndexPath.section] as! [Any]
            var toArray = _iDLMoveableDataSource[toIndexPath.section] as! [Any]
            let fromData = fromArray[fromIndexPath.row]
            let toData = toArray[toIndexPath.row]
            fromArray[fromIndexPath.row] = toData
            toArray[toIndexPath.row] = fromData
            _iDLMoveableDataSource[fromIndexPath.section] = fromArray
            _iDLMoveableDataSource[toIndexPath.section] = toArray
            
            beginUpdates()
            moveRow(at: fromIndexPath, to: toIndexPath)
            moveRow(at: toIndexPath, to: fromIndexPath)
            endUpdates()
        }
    }

    private func iDLSnapshotView(withInputView inputView: UIView) -> UIView {
        UIGraphicsBeginImageContextWithOptions(inputView.bounds.size, false, 0)
        inputView.layer.render(in: UIGraphicsGetCurrentContext()!)
        let image: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        let snapshot: UIView? = UIImageView(image: image)
        return snapshot ?? UIView()
    }

参照：长按即可移动cell的UITableView