显示Swift当前播放的歌曲标题时出现问题

Question

我开始工作了，但当我选择要播放的歌曲时，歌曲的标题并没有第一次出现。我必须回到媒体选择器，再次选择歌曲以显示歌曲的标题。为什么我第一次选择这首歌时它不起作用？另外，当我选择另一首歌播放时，我该如何删除歌曲的标题？非常感谢。这是我的代码：

func mediaPicker(mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {

if mediaItemCollection.items.count == 2{
mediaPicker.dismissViewControllerAnimated(true, completion: nil)

let aMediaItem = mediaItemCollection.items[0] as MPMediaItem
music = aMediaItem
NSLog("(aMediaItem.title)selected")
let url: NSURL = (music.valueForProperty(MPMediaItemPropertyAssetURL) as? NSURL)!
    do {
        musicPlayer = try AVAudioPlayer(contentsOfURL: url)
    } catch {
        return
    }
        titleLabel2.text = music.title
        titleLabel2 = SKLabelNode(fontNamed: "TimeBurner")
        titleLabel2.fontColor = UIColor.whiteColor()
        titleLabel2.zPosition = 40
        titleLabel2.fontSize = 16
        titleLabel2.position = CGPointMake(self.size.width / 5.3, self.size.height / 1.2)
        addChild(titleLabel2)

    let aMediaItem2 = mediaItemCollection.items[1] as MPMediaItem
    music2 = aMediaItem2
    NSLog("(aMediaItem2.title)selected")
    let url2: NSURL = (music2.valueForProperty(MPMediaItemPropertyAssetURL) as? NSURL)!
    do {
        musicPlayer2 = try AVAudioPlayer(contentsOfURL: url2)
    } catch {
        return
    }
    titleLabel.text = music2.title
    titleLabel = SKLabelNode(fontNamed: "TimeBurner")
    titleLabel.fontColor = UIColor.whiteColor()
    titleLabel.zPosition = 40
    titleLabel.fontSize = 16
    titleLabel.position = CGPointMake(self.size.width / 1.3, self.size.height / 1.2)
    addChild(self.titleLabel)
    }
}

Answer 1

下面是我如何让它工作的。我将标题标签添加到didmovetoview中，并将文本添加到didPickMediaItems中。

override func didMoveToView(view: SKView) {
titleLabel2 = SKLabelNode(fontNamed: "TimeBurner")
titleLabel2.fontColor = UIColor.whiteColor()
titleLabel2.zPosition = 40
titleLabel2.fontSize = 16
titleLabel2.position = CGPointMake(self.size.width / 6.0, self.size.height / 1.25)
addChild(titleLabel2)

titleLabel = SKLabelNode(fontNamed: "TimeBurner")
titleLabel.fontColor = UIColor.whiteColor()
titleLabel.zPosition = 40
titleLabel.fontSize = 16
titleLabel.position = CGPointMake(self.size.width / 1.2, self.size.height / 1.25)
addChild(self.titleLabel)
}

  func mediaPicker(mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {

  if mediaItemCollection.items.count == 2{
  mediaPicker.dismissViewControllerAnimated(true, completion: nil)
 let aMediaItem = mediaItemCollection.items[0] as MPMediaItem
 music = aMediaItem
 NSLog("(aMediaItem.title)selected")
  let url: NSURL = (music.valueForProperty(MPMediaItemPropertyAssetURL) as?    NSURL)!
do {
    musicPlayer = try AVAudioPlayer(contentsOfURL: url)
} catch {
    return
}
    titleLabel2.text = music.title

let aMediaItem2 = mediaItemCollection.items[1] as MPMediaItem
music2 = aMediaItem2
NSLog("(aMediaItem2.title)selected")
let url2: NSURL = (music2.valueForProperty(MPMediaItemPropertyAssetURL) as? NSURL)!
do {
    musicPlayer2 = try AVAudioPlayer(contentsOfURL: url2)
} catch {
    return
}
titleLabel.text = music2.title
addChild(self.titleLabel)
}
}