MPRemoteCommandCenter error: the track is played simultaneously several times - ios

Question

I have TableViewController and AudioPlayerViewController. I have a problem with using MPRemoteCommandCenter. For example: In TableViewController I click on cell and go toAudioPlayerViewController next I lock device and control my music with MPRemoteCommandCenter - all works fine. But if I further unlock device return to TableViewController go again to AudioPlayerViewController lock device and press play/pause button my music will play two times at the same time. If I will repeat the action my music will play three times at the same time. And etc... How to fix it?
code:
import UIKit
import AVFoundation
import MediaPlayer
class ViewController: UIViewController, AVAudioPlayerDelegate, UIAlertViewDelegate {
var audioPlayer: AVAudioPlayer!
let musicOperation = OperationQueue()
var timer: Timer?
#IBOutlet weak var playButton: UIButton!
#IBOutlet var timeElapsed: UILabel!
#IBOutlet var timeDuration: UILabel!
#IBOutlet weak var logo: UIImageView!
#IBOutlet weak var slider: UISlider!
#IBOutlet weak var volumeView: UIView!
var index = 0
var buttonIndex = 0
var endOfChapterSleepTimer = false
override func viewDidLoad() {
super.viewDidLoad()
// Table View Index
buttonIndex = masterIndex
musicOperation.maxConcurrentOperationCount = 1
try? AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
UserDefaults.standard.set(index, forKey: "index")
if index > 0 {
let fileManager = FileManager.default
let urls = fileManager.urls(for: .documentDirectory, in: .userDomainMask)
if let documentDirectoryURL: NSURL = urls.first as NSURL? {
let soundURL = documentDirectoryURL.appendingPathComponent("/\(masterIndex)/\(index).mp3")
UserDefaults.standard.set(index, forKey: "\(masterIndex)")
do {
audioPlayer = try AVAudioPlayer(contentsOf: soundURL!)
audioPlayer.delegate = self
audioPlayer.prepareToPlay()
play(sender:AnyObject.self as AnyObject)
restorePlayerCurrentTime()
setupMediaPlayerNotificationView()
lockScreen()
} catch {
}
}
} else {
let url = Bundle.main.url(forResource: "\(masterIndex)0", withExtension: "m4a")!
do {
audioPlayer = try AVAudioPlayer(contentsOf: url)
audioPlayer.delegate = self
audioPlayer.prepareToPlay()
play(sender:AnyObject.self as AnyObject)
setupMediaPlayerNotificationView()
lockScreen()
} catch {
}
}
}
// MARK: - Audio player controller
#IBAction func play(sender: AnyObject) {
if !audioPlayer.isPlaying{
audioPlayer.play()
slider.maximumValue = Float(audioPlayer.duration)
timer = Timer(timeInterval: 0.1, target: self, selector: #selector(self.updateTime), userInfo: nil, repeats: true)
RunLoop.main.add(timer!, forMode: .commonModes)
restorePlayerCurrentTime()
playButton.setImage(UIImage(named: "pause.png"), for: UIControlState.normal)
} else {
audioPlayer.pause()
playButton.setImage(UIImage(named: "play.png"), for: UIControlState.normal)
timer?.invalidate()
}
}
#IBAction func fastForward(sender: AnyObject) {
var time: TimeInterval = audioPlayer.currentTime
time += 15.0 // Go Forward by 15 Seconds
if time > audioPlayer.duration {
audioPlayerDidFinishPlaying(audioPlayer, successfully: true)
} else {
audioPlayer.currentTime = time
updateTime()
}
}
#IBAction func fastBackward(sender: AnyObject) {
var time: TimeInterval = audioPlayer.currentTime
time -= 15.0 // Go Back by 15 Seconds
if time < 0 {
audioPlayer.currentTime = 0
updateTime()
} else {
audioPlayer.currentTime = time
updateTime()
}
}
// MARK: - Audio player time
private func restorePlayerCurrentTime() {
let currentTimeFromUserDefaults : Double? = UserDefaults.standard.value(forKey: "currentTime\(masterIndex)\(index)") as! Double?
if let currentTimeFromUserDefaultsValue = currentTimeFromUserDefaults {
audioPlayer.currentTime = currentTimeFromUserDefaultsValue
slider.value = Float.init(audioPlayer.currentTime)
}
}
#objc func updateTime() {
let currentTime = Int(audioPlayer.currentTime)
let minutes = currentTime/60
let seconds = currentTime - minutes * 60
let durationTime = Int(audioPlayer.duration) - Int(audioPlayer.currentTime)
let minutes1 = durationTime/60
let seconds1 = durationTime - minutes1 * 60
timeElapsed.text = NSString(format: "%02d:%02d", minutes,seconds) as String
timeDuration.text = NSString(format: "-%02d:%02d", minutes1,seconds1) as String
UserDefaults.standard.set(currentTime, forKey: "currentTime\(masterIndex)\(index)")
UserDefaults.standard.set(durationTime, forKey: "durationTime\(masterIndex)\(index)")
slider.value = Float.init(audioPlayer.currentTime)
}
func audioPlayerDidFinishPlaying(_ audioPlayer: AVAudioPlayer, successfully flag: Bool) {
playButton.setImage(UIImage(named: "play.png"), for: UIControlState.normal)
let currentTime = 0
let durationTime = 0.1
UserDefaults.standard.set(currentTime, forKey: "currentTime\(masterIndex)\(index)")
UserDefaults.standard.set(durationTime, forKey: "durationTime\(masterIndex)\(index)")
slider.value = Float.init(audioPlayer.currentTime)
timer?.invalidate()
let path = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)
let documentDirectoryPath:String = path[0]
let fileManager = FileManager()
let destinationURLForFile = URL(fileURLWithPath: documentDirectoryPath.appendingFormat("/\(masterIndex)/\(index+1).mp3"))
if fileManager.fileExists(atPath: destinationURLForFile.path){
index = index + 1
viewDidLoad()
} else {
}
}
// MARK: - Audio player lock screen
func lockScreen() {
var albumArtwork : MPMediaItemArtwork!
let image:UIImage = UIImage(named: "infoImage")!
albumArtwork = MPMediaItemArtwork.init(boundsSize: image.size, requestHandler: { (size) -> UIImage in
return image
})
let infotitle = "title"
MPNowPlayingInfoCenter.default().nowPlayingInfo = [
MPMediaItemPropertyArtist : "",
MPMediaItemPropertyTitle : infotitle,
MPMediaItemPropertyArtwork : albumArtwork,
MPMediaItemPropertyAlbumTitle : "",
MPNowPlayingInfoPropertyElapsedPlaybackTime : Int(audioPlayer.currentTime),
MPMediaItemPropertyPlaybackDuration: Int(audioPlayer.duration)]
}
func setupMediaPlayerNotificationView() {
let commandCenter = MPRemoteCommandCenter.shared()
commandCenter.playCommand.addTarget { event in
self.audioPlayer.play()
self.lockScreen()
self.playButton.setImage(UIImage(named: "pause.png"), for: UIControlState.normal)
print("play")
return .success
}
commandCenter.pauseCommand.addTarget { event in
self.audioPlayer.pause()
self.lockScreen()
self.playButton.setImage(UIImage(named: "play.png"), for: UIControlState.normal)
print("pause")
return .success
}
commandCenter.skipBackwardCommand.preferredIntervals = [15]
commandCenter.skipBackwardCommand.addTarget { event in
self.fastBackward(sender: self)
self.lockScreen()
print("fastBackward")
return .success
}
commandCenter.skipForwardCommand.preferredIntervals = [15]
commandCenter.skipForwardCommand.addTarget { event in
self.fastForward(sender: self)
self.lockScreen()
print("fastForward")
return .success
}
commandCenter.changePlaybackPositionCommand.addTarget(self, action: #selector(self.changedThumbSlider(_:)))
#objc func changedThumbSlider(_ event: MPChangePlaybackPositionCommandEvent) -> MPRemoteCommandHandlerStatus {
let time = event.positionTime
audioPlayer.currentTime = TimeInterval(time)
self.lockScreen()
return .success
}
// MARK: - Audio player slider
#IBAction func slide(_ slider: UISlider) {
musicOperation.cancelAllOperations()
let operation = BlockOperation()
audioPlayer.currentTime = TimeInterval(slider.value)
self.lockScreen()
musicOperation.addOperation(operation)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
audioPlayer.pause()
timer?.invalidate()
musicOperation.cancelAllOperations()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
UIView.setAnimationsEnabled(true)
// Navigation Bar
self.navigationController?.navigationBar.prefersLargeTitles = true
self.navigationItem.largeTitleDisplayMode = .always
self.navigationController?.navigationBar.shadowImage = UIImage()
self.navigationController?.navigationBar.barTintColor = UIColor(red: 55/255, green: 60/255, blue: 65/255, alpha: 1.0)
self.navigationController?.navigationBar.isTranslucent = true
self.navigationController?.navigationBar.tintColor = .white
self.navigationItem.backBarButtonItem = UIBarButtonItem(title: "", style: .plain, target: nil, action: nil)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}

Answer 1

whats happening is that everytime you goto AudioPlayerViewController you enable MPRemoteCommandCenter, however when you go back to TableViewController you are not calling removeTarget. this is your issue.
calling something like the below in viewWillDisappear to removeTarget
func setupMediaPlayerNotificationView(_ enable: Bool) {
let commandCenter = MPRemoteCommandCenter.shared()
if enable {
commandCenter.playCommand.addTarget(self, action: #selector(self.lockScreenPlay(_:)))
commandCenter.pauseCommand.addTarget(self, action: #selector(self.lockScreenPlay(_:)))
commandCenter.nextTrackCommand.addTarget(self, action: #selector(self.lockScreenNextTrack(_:)))
commandCenter.previousTrackCommand.addTarget(self, action: #selector(self.lockScreenPreviousTrack(_:)))
} else {
commandCenter.playCommand.removeTarget(self, action: #selector(self.lockScreenPlay(_:)))
commandCenter.pauseCommand.removeTarget(self, action: #selector(self.lockScreenPlay(_:)))
commandCenter.nextTrackCommand.removeTarget(self, action: #selector(self.lockScreenNextTrack(_:)))
commandCenter.previousTrackCommand.removeTarget(self, action: #selector(self.lockScreenPreviousTrack(_:)))
}
}
example to follow up question:
#objc func lockScreenPlay(_ event: MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus {
self.playButton(AnyObject.self)
return .success
}
#objc func lockScreenNextTrack(_ event: MPRemoteCommandEvent) -> MPRemoteCommandHandlerStatus {
self.playerDidFinishPlaying()
return .success
}