How can I monitor currentPosition of AVMIDIPlayer, please? - swift

Question

I'm trying to make a simple music player. I want the label to display the current position of the AVMIDIPlayer. With my code the label is only updated once at the very beginning:
import UIKit
import AVFoundation
class ViewController: UIViewController {
var player:AVMIDIPlayer = AVMIDIPlayer()
var playerTime:Double = 999 {
didSet {
label.text = String(playerTime)
}
}
#IBOutlet var label: UILabel!
#IBAction func Play(_ sender: Any) {
player.play()
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
do {
let audioPath = Bundle.main.path(forResource: “song”, ofType: "mid")
try player = AVMIDIPlayer(contentsOf: NSURL(fileURLWithPath: audioPath!) as URL, soundBankURL: nil)
playerTime = player.currentPosition
}
catch {
}
}
}
What have I missed, please? Thank you. Scarlett

Answer 1

The reason the label isn’t updating is you’re setting the text in viewDidLoad which is called only once. Use a Timer to update the label.
import UIKit
import AVFoundation
class ViewController: UIViewController {
var player:AVMIDIPlayer = AVMIDIPlayer()
var playerTime:Double = 999 {
didSet {
label.text = String(playerTime)
}
}
var timer = Timer()
#IBOutlet var label: UILabel!
#IBAction func Play(_ sender: Any) {
player.play()
// this will execute every 0.1 seconds, allowing you to update the label.
timer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true) { _ in
self.playerTime += 0.1
let min = self.playerTime.truncatingRemainder(dividingBy: 3600)) / 60
let sec = self.playerTime.truncatingRemainder(dividingBy: 60)
self.label.text = String(format: "%02d:%02d", min, sec)
}
}
func stop() {
// when you stop playback
timer.invalidate()
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
do {
let audioPath = Bundle.main.path(forResource: “song”, ofType: "mid")
try player = AVMIDIPlayer(contentsOf: NSURL(fileURLWithPath: audioPath!) as URL, soundBankURL: nil)
playerTime = player.currentPosition
}
catch {
}
}
}