NotificationCenter stops working when the screen is locked

Question

I'm having trouble with an app I'm building, the app objective is to play audio files, it works by requesting an audio file from a public API, playing it and wait until it ends, after it ends it requests another audio and starts over.

Here's a shortened version of the code that does this, I omitted the error checking part for simplicity

func requestEnded(audioSource: String) {
    let url = URL(string: "https://example.com/audios/" + audioSource)
    audio = AVPlayer(url: url!)
    NotificationCenter.default.addObserver(self,selector: #selector(MediaItem.finishedPlaying(_:)), name: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: audio?.currentItem)
    audio?.play()
}

@objc func finishedPlaying(_ notification: NSNotification) {
    print("Audio ended")
    callAPI()
}

func callAPI() {
    // do all the http request stuff
    requestEnded(audioSource: "x.m4a")
}

// callAPI() is called when the app is initialized

It works well when the screen is unlocked. When I lock the phone the current audio keeps playing but when it ends finishedPlaying() never gets called (the print statement is not shown on the console).

How can I make it so the app would know the audio ended and trigger another one all while locked?, In the android version I got around the screenlock problem by using a partial wakelock which made it run normally even with the screen off.

It has to be done this way because the API decides the audio on realtime and it's all done on the backend so no way to buffer more than one audio without breaking the requirements of the app

What are my options here?, any help is appreciated.

Have you set UIBackgroundModes to audio in your Info.plist? https://developer.apple.com/library/content/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html — charmingToad, Nov 18 '16 at 18:17
Have you set the AVAudioSession category to playback? Code in top answer here: http://stackoverflow.com/questions/30280519/how-to-play-audio-in-background-swift — charmingToad, Nov 18 '16 at 18:34
Yes i set `AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)` when the app loads — Roberto Arosemena, Nov 18 '16 at 18:40
And you also set ```AVAudioSession.sharedInstance().setActive(true)```? — charmingToad, Nov 18 '16 at 18:46
Yes, they are both at the end of the `viewDidLoad()` method of the view controller — Roberto Arosemena, Nov 18 '16 at 18:47
@RobertoArosemena: Is "player" a property of your view controller? — , Nov 18 '16 at 18:52
I'm not sure what you mean with "player" but this code is in a class that gets instanciated by a class that handles the api calls which in turn gets created in the view controller — Roberto Arosemena, Nov 18 '16 at 18:57

NotificationCenter stops working when the screen is locked

0 Answers0