Как слушать нажатие гарнитуры (наушников)?

import UIKit
import MediaPlayer
import AVFoundation

class testVC: UIViewController, {
    
    private var audioLevel : Float = 0.0
    @IBOutlet weak var label1: UILabel!
    var imagePicker: UIImagePickerController!
    
    @IBOutlet weak var imageView: UIImageView!
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }
    
    override func viewWillAppear(_ animated: Bool) {
        listenVolumeButton()
    }
    
    func listenVolumeButton(){
        
        let audioSession = AVAudioSession.sharedInstance()
        do {
            try audioSession.setActive(true, options: [])
            audioSession.addObserver(self, forKeyPath: "outputVolume",
                                     options: NSKeyValueObservingOptions.new, context: nil)
            audioLevel = audioSession.outputVolume
        } catch {
            print("Error")
        }
    }
    
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == "outputVolume"{
             print("GoodBye")
            
            let audioSession = AVAudioSession.sharedInstance()
            if audioSession.outputVolume > audioLevel {
                print("Hello")
                audioLevel = audioSession.outputVolume
            }
            if audioSession.outputVolume < audioLevel {
                print("GoodBye")
                audioLevel = audioSession.outputVolume
            }
            if audioSession.outputVolume > 0.999 {
                (MPVolumeView().subviews.filter{NSStringFromClass($0.classForCoder) == "MPVolumeSlider"}.first as? UISlider)?.setValue(0.9375, animated: false)
                audioLevel = 0.9375
            }
            
            if audioSession.outputVolume < 0.001 {
                (MPVolumeView().subviews.filter{NSStringFromClass($0.classForCoder) == "MPVolumeSlider"}.first as? UISlider)?.setValue(0.0625, animated: false)
                audioLevel = 0.0625
            }
            
        }
    }
    
 
    
}