[英]How can I detect if the stock music app has been terminated?
我正在使用MPMusicPlayerController.systemMusicPlayer()
制作音樂播放器來學習Swift,除了一個小問題,一切都進行得很好。 每當從我的應用程序播放音樂時,然后我切換到音樂應用程序並通過多任務終止它,則音樂會按預期停止,但是當我切換到該應用程序時,我的應用程序會崩潰。 我以為這可能是由於我沒有為音樂終止時應設置的條件設置條件,而且我似乎在Apple Docs中找不到任何真正有用的條件。 我試過了
if (musicPlayer.playbackState == MPMusicPlaybackState.Interrupted) || (musicPlayer.playbackState == MPMusicPlaybackState.Stopped)
無濟於事。 任何人都可以提供一些有關為什么發生這種情況和/或解決方案的見解嗎? 這是我的代碼示例:
override func viewDidLoad() {
super.viewDidLoad()
var notificationCenter = NSNotificationCenter.defaultCenter()
notificationCenter.addObserver(self, selector: "handlePlayingItemChanged", name: MPMusicPlayerControllerNowPlayingItemDidChangeNotification, object: musicPlayer)
notificationCenter.addObserver(self, selector: "handlePlayState", name: MPMusicPlayerControllerPlaybackStateDidChangeNotification, object: musicPlayer)
musicPlayer.beginGeneratingPlaybackNotifications()
if (musicPlayer.playbackState == MPMusicPlaybackState.Playing) {
playButton.setImage(pause, forState: UIControlState.Normal)
setupCurrentMediaItem()
handleShuffleAndReplayMode()
self.isPlay = true
} else if (musicPlayer.playbackState == MPMusicPlaybackState.Paused) {
playButton.setImage(play, forState: UIControlState.Normal)
self.isPlay = false
} else if (musicPlayer.playbackState == MPMusicPlaybackState.Interrupted) || (musicPlayer.playbackState == MPMusicPlaybackState.Stopped) {
playButton.setImage(play, forState: UIControlState.Normal)
self.isPlay = false
}
}
如果不刪除觀察者,則總是會引發異常:
您添加了無條件觀察者以將其刪除:
notificationCenter.addObserver...
刪除觀察者:
notificationCenter.removeObserver...
在此處查找更多信息- 鍵值觀察編程指南
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