Swift中如何捕获全局触摸抬起事件且不影响子视图事件处理？

问题原因 #

你添加的UILongPressGestureRecognizer设置了minimumPressDuration = 0，会在触摸开始时就抢占触摸事件，即便设置了shouldRecognizeSimultaneouslyWith返回true，仍会干扰UIControl（如UIButton）的目标事件响应逻辑，导致子视图的addTarget事件失效。

解决方案一：重写视图触摸事件方法（推荐） #

利用UIKit触摸事件的冒泡机制，直接在ViewController的view中重写touchesEnded方法。子视图的触摸事件会先被处理，之后事件会传递到父视图，既不影响子视图功能，又能全局捕获触摸抬起事件。

修改后代码：

override func viewDidLoad() {
    let button = UIButton(frame: CGRect(x: 0, y: 0, width: 100, height: 50))
    button.setTitle("Click me", for: .normal)
    button.backgroundColor = .blue // 添加背景色便于点击测试
    button.addTarget(self, action: #selector(buttonClick), for: .touchDown)
    self.view.addSubview(button)
    
    // 无需再添加UILongPressGestureRecognizer
}

// 重写view的触摸结束方法
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesEnded(touches, with: event)
    print("Detect global touch end / up")
}

@objc func buttonClick() {
    print("CLICK") // 可正常触发
}

解决方案二：优化手势识别器配置 #

若必须使用手势识别器，需调整代理逻辑并修改手势属性，确保UIControl事件优先响应的同时，手势能正常捕获触摸结束：

extension YourViewController: UIGestureRecognizerDelegate {
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true
    }
    
    // 允许全局手势与UIControl手势同时响应，无需等待UIControl手势失败
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRequireFailureOf otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return otherGestureRecognizer is UIControlGestureRecognizer
    }
}

override func viewDidLoad() {
    let button = UIButton(frame: CGRect(x: 0, y: 0, width: 100, height: 50))
    button.setTitle("Click me", for: .normal)
    button.backgroundColor = .blue
    button.addTarget(self, action: #selector(buttonClick), for: .touchDown)
    self.view.addSubview(button)
    
    initLongTapGesture()
}

func initLongTapGesture () {
    let globalTap = UILongPressGestureRecognizer(target: self, action: #selector(tapHandler))
    globalTap.delegate = self
    globalTap.minimumPressDuration = 0
    // 关闭手势的触摸事件独占性，避免阻断子视图事件
    globalTap.cancelsTouchesInView = false
    self.view.addGestureRecognizer(globalTap)
}

@objc func tapHandler(gesture: UILongPressGestureRecognizer) {
    if [.ended, .cancelled, .failed].contains(gesture.state) {
        print("Detect global touch end / up")
    }
}

@objc func buttonClick() {
    print("CLICK") // 可正常触发
}

内容的提问来源于stack exchange，提问作者AleXiuS