如何在Swift5中侦听按键事件？

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建一个自定义的按键事件处理器
        let keyHandler = KeyHandler()
        
        // 将按键事件处理器添加到当前视图控制器的响应者链中
        self.view.addGestureRecognizer(keyHandler)
    }
}

class KeyHandler: UIGestureRecognizer {
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesBegan(touches, with: event)
        
        // 处理按键按下事件
        print("按键按下")
    }
    
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent) {
        super.touchesEnded(touches, with: event)
        
        // 处理按键释放事件
        print("按键释放")
    }
}