Audio playback progress as UISlider in Swift - ios

Question

I've seen some posts about accomplishing this in Objective-C but I've been unable to do the same via Swift.
Specifically, I can't figure out how to implement addPeriodicTimeObserverForInterval in the below.
var player : AVAudioPlayer! = nil
#IBAction func playAudio(sender: AnyObject) {
playButton.selected = !(playButton.selected)
if playButton.selected {
let fileURL = NSURL(string: toPass)
player = AVAudioPlayer(contentsOfURL: fileURL, error: nil)
player.numberOfLoops = -1 // play indefinitely
player.prepareToPlay()
player.delegate = self
player.play()
startTime.text = "\(player.currentTime)"
endTime.text = NSString(format: "%.1f", player.duration)
} else {
player.stop()
}
Any assistance would be appreciated.

Answer 1

Thanks to the suggestion of Dare above, here's how I accomplished this:
var updater : CADisplayLink! = nil
#IBAction func playAudio(sender: AnyObject) {
playButton.selected = !(playButton.selected)
if playButton.selected {
updater = CADisplayLink(target: self, selector: Selector("trackAudio"))
updater.frameInterval = 1
updater.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSRunLoopCommonModes)
let fileURL = NSURL(string: toPass)
player = AVAudioPlayer(contentsOfURL: fileURL, error: nil)
player.numberOfLoops = -1 // play indefinitely
player.prepareToPlay()
player.delegate = self
player.play()
startTime.text = "\(player.currentTime)"
theProgressBar.minimumValue = 0
theProgressBar.maximumValue = 100 // Percentage
} else {
player.stop()
}
}
func trackAudio() {
var normalizedTime = Float(player.currentTime * 100.0 / player.duration)
theProgressBar.value = normalizedTime
}
#IBAction func cancelClicked(sender: AnyObject) {
player.stop()
updater.invalidate()
dismissViewControllerAnimated(true, completion: nil)
}

Answer 2

Just to elaborate on my previous comment, this is how I implemented it and it seems to work pretty well. Any Swift corrections are more than welcome, I'm still an Obj-C guy for now.
#IBAction func playAudio(sender: AnyObject) {
var playing = false
if let currentPlayer = player {
playing = player.playing;
}else{
return;
}
if !playing {
let filePath = NSBundle.mainBundle().pathForResource("3e6129f2-8d6d-4cf4-a5ec-1b51b6c8e18b", ofType: "wav")
if let path = filePath{
let fileURL = NSURL(string: path)
player = AVAudioPlayer(contentsOfURL: fileURL, error: nil)
player.numberOfLoops = -1 // play indefinitely
player.prepareToPlay()
player.delegate = self
player.play()
displayLink = CADisplayLink(target: self, selector: ("updateSliderProgress"))
displayLink.addToRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode!)
}
} else {
player.stop()
displayLink.invalidate()
}
}
func updateSliderProgress(){
var progress = player.currentTime / player.duration
timeSlider.setValue(Float(progress), animated: false)
}
*I set time slider's range between 0 and 1 on a storyboard

Answer 3

Specifically for Swift I was able to handle it like this:
I set the maximum value of the scrubSlider to the duration of the music file(.mp3) that was loaded in this method
override func viewDidLoad() {
super.viewDidLoad()
do {
try player = AVAudioPlayer(contentsOfURL: NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("bach", ofType: "mp3")!))
scrubSlider.maximumValue = Float(player.duration)
} catch {
//Error
}
_ = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: #selector(ViewController.updateScrubSlider), userInfo: nil, repeats: true)
}
I player was set to play the music at the time set by the value of the scrubber.
#IBAction func scrub(sender: AnyObject) {
player.currentTime = NSTimeInterval(scrubSlider.value)
}

Answer 4

Syntax has now changed in Swift 4:
updater = CADisplayLink(target: self, selector: #selector(self.trackAudio))
updater.preferredFramesPerSecond = 1
updater.add(to: RunLoop.current, forMode: RunLoopMode.commonModes)
And the function (I have previously set the progressSlider.maxValue to player.duration):
#objc func trackAudio() {
progressSlider.value = Float(player!.currentTime)
}