如何在UIButton上按下双按钮取消操作？

let button1 = UIButton(type: .system)
button1.setTitle("Button 1", for: .normal)
button1.frame = CGRect(x: 50, y: 100, width: 100, height: 50)

let button2 = UIButton(type: .system)
button2.setTitle("Button 2", for: .normal)
button2.frame = CGRect(x: 200, y: 100, width: 100, height: 50)

button1.addTarget(self, action: #selector(button1Tapped), for: .touchUpInside)
button2.addTarget(self, action: #selector(button2Tapped), for: .touchUpInside)

var button1Timer: DispatchSourceTimer?
var button2Timer: DispatchSourceTimer?

@objc func button1Tapped() {
    if button1Timer == nil {
        let queue = DispatchQueue(label: "com.example.button1", attributes: .concurrent)
        button1Timer = DispatchSource.makeTimerSource(queue: queue)
        button1Timer?.schedule(deadline: .now() + 0.5, repeating: 0.5)
        button1Timer?.setEventHandler { [weak self] in
            DispatchQueue.main.async {
                self?.button1.setTitle("Cancel", for: .normal)
            }
        }
        button1Timer?.resume()
    } else {
        button1Timer?.cancel()
        button1Timer = nil
        button1.setTitle("Button 1", for: .normal)
    }
}

@objc func button2Tapped() {
    if button2Timer == nil {
        let queue = DispatchQueue(label: "com.example.button2", attributes: .concurrent)
        button2Timer = DispatchSource.makeTimerSource(queue: queue)
        button2Timer?.schedule(deadline: .now() + 0.5, repeating: 0.5)
        button2Timer?.setEventHandler { [weak self] in
            DispatchQueue.main.async {
                self?.button2.setTitle("Cancel", for: .normal)
            }
        }
        button2Timer?.resume()
    } else {
        button2Timer?.cancel()
        button2Timer = nil
        button2.setTitle("Button 2", for: .normal)
    }
}

view.addSubview(button1)
view.addSubview(button2)