Denis Paul Denis Paul - 2 months ago 10
iOS Question

How to automatically go to the next track when the the one is currently playing ends?

I'm quite new to swift and I want to implement a piece of code that helps me reach the next song when the one that is currently playing ends.
I tried to copy the code inside my "@IBAction func nextAction" (which works fine):

@IBAction func nextAction(sender: AnyObject) {
self.nextTrack()
}

func nextTrack() {

if trackId == 0 || trackId < 4 {
if shuffle.on {
trackId = Int(arc4random_uniform(UInt32(library.count)))
}else {
trackId += 1
}

if let coverImage = library[trackId]["coverImage"]{
coverImageView.image = UIImage(named: "\(coverImage).jpg")
}

songTitleLabel.text = library[trackId]["title"]
artistLabel.text = library[trackId]["artist"]

audioPlayer.currentTime = 0
progressView.progress = 0

let path = NSBundle.mainBundle().pathForResource("\(trackId)", ofType: "mp3")

if let path = path {
let mp3URL = NSURL(fileURLWithPath: path)

do {
audioPlayer = try AVAudioPlayer(contentsOfURL: mp3URL)
audioPlayer.play()

NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(PlayerViewController.updateProgressView), userInfo: nil, repeats: true)
progressView.setProgress(Float(audioPlayer.currentTime/audioPlayer.duration), animated: false)

} catch let error as NSError {
print(error.localizedDescription)
}
}
}

}


And tried to put it inside an if condition like this (inside the viewDidLoad):

if audioPlayer.currentTime >= audioPlayer.duration {
self.nextTrack()
}


I don't have any errors but at runtime this method isn't working and the song ends without playing the next one.

To make the situation more clear here's my controller:

import UIKit
import AVFoundation

class PlayerViewController: UIViewController {

@IBOutlet weak var coverImageView: UIImageView!
@IBOutlet weak var progressView: UIProgressView!
@IBOutlet weak var songTitleLabel: UILabel!
@IBOutlet weak var artistLabel: UILabel!
@IBOutlet weak var shuffle: UISwitch!

var trackId: Int = 0
var library = MusicLibrary().library
var audioPlayer: AVAudioPlayer!

override func viewDidLoad() {
super.viewDidLoad()


// Do any additional setup after loading the view.
if let coverImage = library[trackId]["coverImage"]{
coverImageView.image = UIImage(named: "\(coverImage).jpg")
}

songTitleLabel.text = library[trackId]["title"]
artistLabel.text = library[trackId]["artist"]

let path = NSBundle.mainBundle().pathForResource("\(trackId)", ofType: "mp3")

if let path = path {
let mp3URL = NSURL(fileURLWithPath: path)

do {
audioPlayer = try AVAudioPlayer(contentsOfURL: mp3URL)
audioPlayer.play()

NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(PlayerViewController.updateProgressView), userInfo: nil, repeats: true)
progressView.setProgress(Float(audioPlayer.currentTime/audioPlayer.duration), animated: false)

} catch let error as NSError {
print(error.localizedDescription)
}
}

}

override func viewWillDisappear(animated: Bool) {
audioPlayer.stop()
}

func updateProgressView(){

if audioPlayer.playing {

progressView.setProgress(Float(audioPlayer.currentTime/audioPlayer.duration), animated: true)
}

}


@IBAction func playAction(sender: AnyObject) {
if !audioPlayer.playing {
audioPlayer.play()
}

}

@IBAction func stopAction(sender: AnyObject) {

audioPlayer.stop()
audioPlayer.currentTime = 0
progressView.progress = 0
}


@IBAction func pauseAction(sender: AnyObject) {
audioPlayer.pause()
}

@IBAction func fastForwardAction(sender: AnyObject) {
var time: NSTimeInterval = audioPlayer.currentTime
time += 5.0

if time > audioPlayer.duration {
stopAction(self)
}else {
audioPlayer.currentTime = time
}

}

@IBAction func rewindAction(sender: AnyObject) {
var time: NSTimeInterval = audioPlayer.currentTime
time -= 5.0

if time < 0 {
stopAction(self)
}else {
audioPlayer.currentTime = time
}
}

@IBAction func previousAction(sender: AnyObject) {
if trackId != 0 || trackId > 0 {
if shuffle.on {
trackId = Int(arc4random_uniform(UInt32(library.count)))
}else {
trackId -= 1
}

if let coverImage = library[trackId]["coverImage"]{
coverImageView.image = UIImage(named: "\(coverImage).jpg")
}

songTitleLabel.text = library[trackId]["title"]
artistLabel.text = library[trackId]["artist"]

audioPlayer.currentTime = 0
progressView.progress = 0

let path = NSBundle.mainBundle().pathForResource("\(trackId)", ofType: "mp3")

if let path = path {
let mp3URL = NSURL(fileURLWithPath: path)

do {
audioPlayer = try AVAudioPlayer(contentsOfURL: mp3URL)
audioPlayer.play()

NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(PlayerViewController.updateProgressView), userInfo: nil, repeats: true)
progressView.setProgress(Float(audioPlayer.currentTime/audioPlayer.duration), animated: false)

} catch let error as NSError {
print(error.localizedDescription)
}
}
}




}

@IBAction func swipeDownAction(sender: AnyObject) {
self.close()
}

@IBAction func closeAction(sender: AnyObject) {
self.close()
}

@IBAction func nextAction(sender: AnyObject) {
self.nextTrack()
}

func close() {
self.dismissViewControllerAnimated(true, completion: nil)
}


func nextTrack() {

if trackId == 0 || trackId < 4 {
if shuffle.on {
trackId = Int(arc4random_uniform(UInt32(library.count)))
}else {
trackId += 1
}

if let coverImage = library[trackId]["coverImage"]{
coverImageView.image = UIImage(named: "\(coverImage).jpg")
}

songTitleLabel.text = library[trackId]["title"]
artistLabel.text = library[trackId]["artist"]

audioPlayer.currentTime = 0
progressView.progress = 0

let path = NSBundle.mainBundle().pathForResource("\(trackId)", ofType: "mp3")

if let path = path {
let mp3URL = NSURL(fileURLWithPath: path)

do {
audioPlayer = try AVAudioPlayer(contentsOfURL: mp3URL)
audioPlayer.play()

NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(PlayerViewController.updateProgressView), userInfo: nil, repeats: true)
progressView.setProgress(Float(audioPlayer.currentTime/audioPlayer.duration), animated: false)

} catch let error as NSError {
print(error.localizedDescription)
}
}
}

}
}


All the code is written in Xcode 7.3.1

Answer

You should use AVAudioPlayer delegate method audioPlayerDidFinishPlaying(player: AVAudioPlayer, successfully flag: Bool) which is called when the audio player finishes playing a sound.

  1. Make your PlayerViewController confirm to AVAudioPlayerDelegate protocol like this:

    class PlayerViewController: UIViewController, AVAudioPlayerDelegate {
    
  2. Make sure to set self as the delegate of the audioPlayer you create, to do that in your viewDidLoad,previousAction and nextTrack method you need to add

    audioPlayer.delegate = self
    

    after this line:

    audioPlayer = try AVAudioPlayer(contentsOfURL: mp3URL)
    
  3. Now you can use the delegate method to know when the audio is finished playing and go to the next track, just add this inside your class:

    func audioPlayerDidFinishPlaying(player: AVAudioPlayer, successfully flag: Bool) {
        if flag {
            self.nextTrack()
        } else {
            // did not finish successfully
        }
    }
    
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