当在UIAlertController外部单击时，请不要忽略它

let alertController = UIAlertController(title: "提示", message: "这是一个弹窗", preferredStyle: .alert)
let cancelAction = UIAlertAction(title: "取消", style: .cancel, handler: nil)
alertController.addAction(cancelAction)

let alertController = UIAlertController(title: "提示", message: "这是一个弹窗", preferredStyle: .alert)

// 添加背景视图
let backgroundView = UIView(frame: alertController.view.bounds)
backgroundView.backgroundColor = UIColor.black.withAlphaComponent(0.5)
alertController.view.addSubview(backgroundView)

// 添加点击事件
let tapGesture = UITapGestureRecognizer(target: self, action: #selector(dismissAlertController))
backgroundView.addGestureRecognizer(tapGesture)

// 显示弹窗
self.present(alertController, animated: true, completion: nil)

// 处理点击事件
@objc func dismissAlertController() {
    alertController.dismiss(animated: true, completion: nil)
}