Ios – Play background music in app

audioavaudioplayeravfoundationiosswift

I want the user to be able to open the app and have music start playing. I want the user to be able to go any view controller and return back to the initial one without the music stopping. I want it to loop indefinitely.

I have tried to put in the viewDidLoad method of the initial view controller for it to start playing. What happens is, the user leaves the initial view controller and when they come back, the music starts playing again, overlapping the original copy.

To remedy this, I put an if statement checking if the sound is already to playing to not launch another copy and the viewDidLoad method completely ignores the if statement and plays it again anyways. I also tried using viewDid/WillAppear. I have tried putting the sound in the app delegate in the applicationDidLaunchWithOptions method and I got complete silence.

Best Answer

Using a singleton works as well:

Swift 3 or later

import AVFoundation

class MusicHelper {
    static let sharedHelper = MusicHelper()
    var audioPlayer: AVAudioPlayer?
    
    func playBackgroundMusic() {
        let aSound = NSURL(fileURLWithPath: Bundle.main.path(forResource: "coolsong", ofType: "mp3")!)
        do {
            audioPlayer = try AVAudioPlayer(contentsOf:aSound as URL)
            audioPlayer!.numberOfLoops = -1
            audioPlayer!.prepareToPlay()
            audioPlayer!.play()
        } catch {
            print("Cannot play the file")
        }
    }
}

Swift 2.2.1 or earlier

import AVFoundation

class MusicHelper {
    static let sharedHelper = MusicHelper()
    var audioPlayer: AVAudioPlayer?
    
    func playBackgroundMusic() {
        let aSound = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("coolsong", ofType: "mp3")!)
        do {
            audioPlayer = try AVAudioPlayer(contentsOfURL:aSound)
            audioPlayer!.numberOfLoops = -1
            audioPlayer!.prepareToPlay()
            audioPlayer!.play()
        } catch {
            print("Cannot play the file")
        }
    }
}

Then you can use it from any class (as per Swift 2.1)

MusicHelper.sharedHelper.playBackgroundMusic()

Swift

Short answer

Use a NotificationCenter observer rather than viewWillAppear.

override func viewDidLoad() {
    super.viewDidLoad()

    // set observer for UIApplication.willEnterForegroundNotification
    NotificationCenter.default.addObserver(self, selector: #selector(willEnterForeground), name: UIApplication.willEnterForegroundNotification, object: nil)

}

// my selector that was defined above
@objc func willEnterForeground() {
    // do stuff
}

Long answer

To find out when an app comes back from the background, use a NotificationCenter observer rather than viewWillAppear. Here is a sample project that shows which events happen when. (This is an adaptation of this Objective-C answer.)

import UIKit
class ViewController: UIViewController {

    // MARK: - Overrides

    override func viewDidLoad() {
        super.viewDidLoad()
        print("view did load")

        // add notification observers
        NotificationCenter.default.addObserver(self, selector: #selector(didBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(willEnterForeground), name: UIApplication.willEnterForegroundNotification, object: nil)

    }

    override func viewWillAppear(_ animated: Bool) {
        print("view will appear")
    }

    override func viewDidAppear(_ animated: Bool) {
        print("view did appear")
    }

    // MARK: - Notification oberserver methods

    @objc func didBecomeActive() {
        print("did become active")
    }

    @objc func willEnterForeground() {
        print("will enter foreground")
    }

}

On first starting the app, the output order is:

view did load
view will appear
did become active
view did appear

After pushing the home button and then bringing the app back to the foreground, the output order is:

will enter foreground
did become active

So if you were originally trying to use viewWillAppear then UIApplication.willEnterForegroundNotification is probably what you want.

Note

As of iOS 9 and later, you don't need to remove the observer. The documentation states:

If your app targets iOS 9.0 and later or macOS 10.11 and later, you don't need to unregister an observer in its dealloc method.

Best Answer

Related Solutions

Ios – Why does viewWillAppear not get called when an app comes back from the background

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Note

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