How to handle background audio playing while iOS device is locked or on another application?

Question

Designing a generative music system for iOS, using OpenFrameworks, I'd need to provide a mode in which the user could listen the music produced by the application when:

• the device is locked
• the user uses another application

Some applications like BLOOM, or alarm clock, works like that and propose to users a switch to enable/disable this feature.

Any tips for that ?

Answer 1

Playing Background Audio

An app that plays or records audio continuously (even while the app is running in the background) can register to perform those tasks in the background. You enable audio support from the Background modes section of the Capabilities tab in your Xcode project. (You can also enable this support by including the UIBackgroundModes key with the audio value in your app’s Info.plist file.) Apps that play audio content in the background must play audible content and not silence.

Apple reference "Playing and Recording Background Audio"

Ensuring That Audio Continues When the Screen Locks

For enabling/disabling this feature I found Activating and Deactivating Your Audio Session, I haven't tried it myself, but it looks like what you need.

Answer 2

Make the following changes in xCode project settings as well as in code.

step 1) Select your project file in the Navigator of Xcode. Then, from the Capabilities section, switch on the Background Modes subsection. After the list of background modes is given to you, tick on the Audio & Airplay switch.

stp 2) Use following swift code, basically you need to set audio session for your app.

var audioPlayer : AVAudioPlayer!

@IBAction func playButtonClicked(sender : AnyObject){

    let dispatchQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
    dispatch_async(dispatchQueue, {

        if let data = NSData(contentsOfFile: self.audioFilePath())
        {
            do{
                let session = AVAudioSession.sharedInstance()

                try session.setCategory(AVAudioSessionCategoryPlayback)
                try session.setActive(true)

                self.audioPlayer = try AVAudioPlayer(data: data)
                //self.audioPlayer.delegate = self
                self.audioPlayer.prepareToPlay()
                self.audioPlayer.play()
            }
            catch{
                print("\(error)")
            }
        }
    });
}

func audioFilePath() -> String{

    let filePath = NSBundle.mainBundle().pathForResource("mySong", ofType: "mp3")!
    return filePath
}

This audio playback session will be play your application playback, even if app is in background or phone is in silent mode or device is locked.

Answer 3

Look at on this tutorial. It has some of background services example

http://www.raywenderlich.com/29948/backgrounding-for-ios

Answer 4

You need to make couple of changes in plist file.

i.e. 1) Set Required background mode to App plays audio

2) set Application does not run in background to NO.

 NSError *setCategoryErr = nil;
 NSError *activationErr  = nil;
 [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error:&setCategoryErr];
 [[AVAudioSession sharedInstance] setActive:YES error:&activationErr];

Then, you need to write these much code in AppDelegate

Now, you can easily run audio while phone screen locks or goes in background.