iOS: AVPlayer plays multiple instances of audio when using controls on lock screen

Question

I have set up a function that creates an AVPlayerViewController instance in order to play an audio track (stored in our server).

func playAudio(_ url: URL) {
    let avAssest = AVAsset(url: url)
    let playerItem = AVPlayerItem(asset: avAssest)

    audioPlayer = AVPlayer(playerItem: playerItem)

    let playerViewController = AVPlayerViewController()
    playerViewController.player = audioPlayer

    try? AVAudioSession.sharedInstance().setCategory(.playback, mode: .default, options: [])

    self.present(playerViewController, animated: true, completion: {
        self.audioPlayer.play()

    })
}

The player works fine while in the foreground. If I go to the lock screen, the audio continues to play. If I press the Pause button in the lock screen, the audio pauses. The problem is, if I then click play on the lock screen, the audio I was listening to resumes, but a second instance of the audio starts playing from the start, so now i have 2 instances of the audio playing simultaneously. If I pause again and press play again, yet another instance of the audio starts playing.

How can I fix this so the lock screen buttons only affect the original audio?

I'm working on Xcode 11, with Swift 4.2.

Answer 1

The problem cannot be reproduced based on the code you showed. Therefore it sounds like you have an extra reference somewhere to self.audioPlayer, and the problem is caused by code you did not reveal to us.

To test that theory, let's start by not making it a global. There's no need for that within the scope of the question.

Modify your code to look like this (note the changes to make this a local):

    let avAssest = AVAsset(url: url)
    let playerItem = AVPlayerItem(asset: avAssest)

    let audioPlayer = AVPlayer(playerItem: playerItem) // *

    let playerViewController = AVPlayerViewController()
    playerViewController.player = audioPlayer

    try? AVAudioSession.sharedInstance().setCategory(.playback, mode: .default, options: [])

    self.present(playerViewController, animated: true, completion: {
        audioPlayer.play()  // *

    })

Now delete the audioPlayer property and, if your code fails to compile, comment out everything that refers to it until the code does compile. Test the app; all is well. Now go back and figure out where in the code you did not show us the problem is coming from.