如何实现UIPanGestureRecognizer在多子视图上的跨视图回调？

嘿，这个需求我刚好碰到过，有几个比硬算frame优雅得多的实现方式，给你捋捋：

方案一：利用系统hitTest+路径追踪（适合已有自定义视图） #

不用自己手动计算子视图的frame，直接借助UIKit的hitTest(_:with:)方法让系统帮你定位当前手势命中的视图。为了避免快速滑动跳过中间子视图，还可以结合路径追踪，检查滑动线段经过的所有子视图：

首先在自定义View里定义几个追踪用的属性：

class TicTacToeView: UIView {
    private var currentSelectedSubview: UIView?
    private var lastGestureLocation: CGPoint?
    
    override init(frame: CGRect) {
        super.init(frame: frame)
        setupPanGesture()
        setupSubviews() // 你的9个子视图布局逻辑
    }
    
    required init?(coder: NSCoder) {
        super.init(coder: coder)
        setupPanGesture()
        setupSubviews()
    }
    
    private func setupPanGesture() {
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
        addGestureRecognizer(panGesture)
    }
}

然后实现手势处理方法：

@objc private func handlePan(_ gesture: UIPanGestureRecognizer) {
    let currentLocation = gesture.location(in: self)
    
    switch gesture.state {
    case .began:
        // 记录初始位置，处理第一个命中的子视图
        lastGestureLocation = currentLocation
        guard let hitView = hitTest(currentLocation, with: nil), subviews.contains(hitView) else { return }
        performAction(for: hitView)
        currentSelectedSubview = hitView
        
    case .changed:
        guard let lastLoc = lastGestureLocation else { return }
        
        // 创建滑动路径的线段
        let swipePath = UIBezierPath()
        swipePath.move(to: lastLoc)
        swipePath.addLine(to: currentLocation)
        
        // 遍历所有子视图，检查路径是否穿过该视图
        for subview in subviews {
            let subviewFramePath = UIBezierPath(rect: subview.frame)
            if swipePath.intersects(subviewFramePath), subview != currentSelectedSubview {
                performAction(for: subview)
                currentSelectedSubview = subview
            }
        }
        lastGestureLocation = currentLocation
        
    case .ended, .cancelled:
        // 重置追踪状态
        currentSelectedSubview = nil
        lastGestureLocation = nil
        
    default:
        break
    }
}

// 你自己的操作逻辑，比如根据子视图的tag或者索引执行对应动作
private func performAction(for subview: UIView) {
    print("触发子视图操作：\(subview.tag)")
    // 这里写你的具体业务代码
}

这个方案的好处是完全利用系统API，不用自己维护frame计算，代码可读性和可维护性都很高，还能处理快速滑动的场景。

方案二：用UICollectionView简化布局与手势处理（推荐新实现） #

如果你的井字棋布局还没完全定型，直接用UICollectionView会更省心——它帮你搞定子视图（Cell）的布局、复用，甚至可以直接通过indexPathForItem(at:)获取手势位置对应的Cell：

首先设置CollectionView的布局为3列的FlowLayout：

class TicTacToeViewController: UIViewController {
    private var collectionView: UICollectionView!
    private var currentIndexPath: IndexPath?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        setupCollectionView()
        setupPanGesture()
    }
    
    private func setupCollectionView() {
        let layout = UICollectionViewFlowLayout()
        let itemSize = (view.bounds.width - 2*10)/3 // 假设间距是10
        layout.itemSize = CGSize(width: itemSize, height: itemSize)
        layout.minimumLineSpacing = 10
        layout.minimumInteritemSpacing = 10
        layout.sectionInset = UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
        
        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
        collectionView.register(TicTacToeCell.self, forCellWithReuseIdentifier: "Cell")
        collectionView.dataSource = self
        collectionView.delegate = self
        view.addSubview(collectionView)
    }
    
    private func setupPanGesture() {
        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
        collectionView.addGestureRecognizer(panGesture)
    }
}

// 实现UICollectionViewDataSource
extension TicTacToeViewController: UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 9
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) as! TicTacToeCell
        // 配置Cell样式
        return cell
    }
}

然后处理手势：

@objc private func handlePan(_ gesture: UIPanGestureRecognizer) {
    let currentLocation = gesture.location(in: collectionView)
    
    switch gesture.state {
    case .began:
        guard let indexPath = collectionView.indexPathForItem(at: currentLocation) else { return }
        performAction(for: indexPath)
        currentIndexPath = indexPath
        
    case .changed:
        guard let lastIndexPath = currentIndexPath else { return }
        
        // 同样可以加路径追踪优化快速滑动的情况，逻辑和方案一类似
        let lastLocation = collectionView.layoutAttributesForItem(at: lastIndexPath)?.center ?? currentLocation
        let swipePath = UIBezierPath()
        swipePath.move(to: lastLocation)
        swipePath.addLine(to: currentLocation)
        
        // 遍历所有可见Cell，或者所有Item，检查路径是否穿过
        for indexPath in collectionView.indexPathsForVisibleItems {
            guard let attributes = collectionView.layoutAttributesForItem(at: indexPath) else { continue }
            let cellPath = UIBezierPath(rect: attributes.frame)
            if swipePath.intersects(cellPath), indexPath != lastIndexPath {
                performAction(for: indexPath)
                currentIndexPath = indexPath
            }
        }
        
    case .ended, .cancelled:
        currentIndexPath = nil
        
    default:
        break
    }
}

private func performAction(for indexPath: IndexPath) {
    print("触发第\(indexPath.item)个Cell的操作")
    // 业务逻辑代码
}

用CollectionView的好处是后期如果要修改布局（比如改成4x4），只需要调整FlowLayout的参数即可，完全不用修改手势逻辑，扩展性极强。

额外注意事项 #

• 如果你的子视图有自己的手势，需要设置UIGestureRecognizerDelegate的gestureRecognizer(_:shouldRecognizeSimultaneouslyWith:)方法返回true，避免手势冲突。
• 路径追踪的逻辑可以根据需求调整精度，比如用CGPath的intersection方法做更精确的判断。

内容的提问来源于stack exchange，提问作者kmell96