UIKit中如何在子视图间传递手势，实现跨边界拖拽检测？

iOS系统的触摸事件派发规则里，hitTest(_:with:) 仅会在手指首次按下触发touchesBegan时执行一次，用来确定本次触摸序列的第一响应者。后续手指拖拽移动、抬起的全流程中，所有触摸事件都会固定发送给这个初始命中的视图，不会因为手指滑入其他视图边界就重新执行hitTest切换响应对象，这就是拖拽过程中途经的子视图无法收到事件的核心原因。

不需要修改系统事件传递链做手势穿透，直接在根视图上统一跟踪全流程的触摸位置，实时判断当前手指落点覆盖的子视图并触发反馈即可，逻辑稳定且不会和原有点击逻辑冲突。

代码修改 #

替换你原有的TestView实现即可：

class TestView: UIView {
    // 记录上一次触摸位置命中的视图，避免重复触发反馈
    private var lastHitViews: Set<UIView> = []
    
    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        // 保留原有点击场景的命中逻辑，不影响正常点击响应
        guard isUserInteractionEnabled, !isHidden, alpha > 0.01 else { return nil }
        guard point(inside: point, with: event) else { return nil }
        
        for subview in subviews.reversed() {
            let convertedPoint = convert(point, to: subview)
            guard let hitView = subview.hitTest(convertedPoint, with: event) else { continue }
            return hitView
        }
        return self
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesBegan(touches, with: event)
        checkCoveredViews(with: touches)
    }
    
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesMoved(touches, with: event)
        checkCoveredViews(with: touches)
    }
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)
        lastHitViews.removeAll()
    }
    
    override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesCancelled(touches, with: event)
        lastHitViews.removeAll()
    }
    
    private func checkCoveredViews(with touches: Set<UITouch>) {
        guard let touch = touches.first else { return }
        let touchPoint = touch.location(in: self)
        var currentHitViews = Set<UIView>()
        
        // 遍历所有子视图，判断当前触摸点是否落在视图范围内
        for subview in subviews {
            let pointInSub = convert(touchPoint, to: subview)
            guard subview.point(inside: pointInSub, with: nil) else { continue }
            currentHitViews.insert(subview)
            
            // 首次进入该视图范围时触发反馈
            if !lastHitViews.contains(subview) {
                subview.backgroundColor = .red
            }
        }
        
        // 如果需要手指离开视图时恢复原有颜色，可在此处遍历lastHitViews做差集后重置颜色
        lastHitViews = currentHitViews
    }
}

注意事项 #

• 上述代码完全兼容你现有三层叠加视图的布局，从屏幕任意位置按下拖拽，途经的子视图都会在手指进入边界时触发变红反馈
• 如果需要实现手指离开视图后恢复原始背景色，可以给UIView添加关联属性存储初始背景色，在检测到手指离开视图范围时赋值还原即可
• 不要尝试在touchesMoved阶段强制调用hitTest切换第一响应者，会破坏系统原生事件派发逻辑，引发手势断触、交互冲突等问题

内容的提问来源于stack exchange，提问作者CodeyTown