¿Cómo puedo definir MPMediaItemPropertyArtwork en swift?

Quiero agregar la image de portada que se muestra en la pantalla de locking. ¿Cómo puedo hacerlo? Intenté MPMediaItemPropertyArtwork, pero no se muestra nada. ¿Hay un método de sobrescritura que no puedo ver y bloquea la image de la cubierta de la pantalla de locking?

import UIKit import AVFoundation import MediaPlayer

class ViewController: UIViewController { @IBOutlet weak var statusLabel: UILabel! @IBOutlet weak var playButton: UIButton! var player:AVPlayer = AVPlayer(URL: NSURL(string: "http://www.liveatc.net/play/ltba.pls")) override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. statusLabel.text = "Status: Not Playing" playButton.setTitle("Play", forState: UIControlState.Normal) if NSClassFromString("MPNowPlayingInfoCenter") != nil { let image:UIImage = UIImage(named: "playerBg")! let albumArt = MPMediaItemArtwork(image: image) var songInfo: NSMutableDictionary = [ MPMediaItemPropertyTitle: "LiveATC", MPMediaItemPropertyArtist: "Istanbul Ataturk - LTBA", MPMediaItemPropertyArtwork: albumArt ] MPNowPlayingInfoCenter.defaultCenter().nowPlayingInfo = songInfo as [NSObject : AnyObject] } if (AVAudioSession.shanetworkingInstance().setCategory(AVAudioSessionCategoryPlayback, error: nil)) { println("Receiving remote control events") UIApplication.shanetworkingApplication().beginReceivingRemoteControlEvents() } else { println("Audio Session error.") } // if Reachability.isConnectedToNetwork() == true { // println("Internet connection OK") // } else { // println("Internet connection FAILED") // var alert = UIAlertView(title: "No Internet Connection", message: "Make sure your device is connected to the internet.", delegate: nil, cancelButtonTitle: "OK") // alert.show() // } switch Reachability.isConnectedToNetwork() { case false : println("Internet connection FAILED") var alert = UIAlertView(title: "No Internet Connection", message: "Make sure your device is connected to the internet.", delegate: nil, cancelButtonTitle: "OK") alert.show() fallthrough default: println("Internet connection OK") } } @IBAction func sliderValueChanged(sender: UISlider) { var currentValue = Float(sender.value) println(currentValue) player.volume = currentValue } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. } @IBAction func buttonPressed(sender: AnyObject) { toggle() } func toggle() { if playButton.titleLabel?.text == "Play" { playRadio() println("Playing") statusLabel.text = "Status: Playing" } else { pauseRadio() println("Paused") statusLabel.text = "Status: Paused" } } func playRadio() { player.play() playButton.setTitle("Pause", forState: UIControlState.Normal) } func pauseRadio() { player.pause() playButton.setTitle("Play", forState: UIControlState.Normal) } override func remoteControlReceivedWithEvent(event: UIEvent) { if event.type == UIEventType.RemoteControl { if event.subtype == UIEventSubtype.RemoteControlPlay { println("received remote play") playRadio() } else if event.subtype == UIEventSubtype.RemoteControlPause { println("received remote pause") pauseRadio() } else if event.subtype == UIEventSubtype.RemoteControlTogglePlayPause { println("received toggle") toggle() } } } }