import UIKitclass ViewController: UIViewController {    deinit {        NotificationCenter.default.removeObserver(self)    }    override func viewDidLoad() {        super.viewDidLoad()               //开启距离传感器功能        UIDevice.current.isProximityMonitoringEnabled = true                //监听物体开进或离开设备的通知        NotificationCenter.default.addObserver(self, selector: #selector(statusChange), name: UIDevice.proximityStateDidChangeNotification, object: nil)            }    /// 这个主要在 手机上方，电话听筒有相应  = =  下面没得反应    @objc func statusChange(){        //获取当前是否有物体靠近设备                if UIDevice.current.proximityState {            print("大佬来了")        }else{            print("大佬走了")        }    }}