Add event for queue index changes

SwiftAudioEx/Classes/Event.swift

@@ -18,6 +18,7 @@ extension AudioPlayer {
     public typealias UpdateDurationEventData = (Double)
     public typealias MetadataEventData = ([AVMetadataItem])
     public typealias DidRecreateAVPlayerEventData = ()
+    public typealias QueueIndexEventData = (previousIndex: Int?, newIndex: Int?)
 
     public struct EventHolder {
 
@@ -70,7 +71,13 @@ extension AudioPlayer {
          - Note: It can be necessary to set the AVAudioSession's category again when this event is emitted.
          */
         public let didRecreateAVPlayer: AudioPlayer.Event<()> = AudioPlayer.Event()
-
+
+        /**
+         Emitted when a new track starts and the queue index changes.
+         - Important: Remember to dispatch to the main queue if any UI is updated in the event handler.
+         - Note: It is only fired for instances of a QueuedAudioPlayer.
+         */
+        public let queueIndex: AudioPlayer.Event<QueueIndexEventData> = AudioPlayer.Event()
     }
 
     public typealias EventClosure<EventData> = (EventData) -> Void

SwiftAudioEx/Classes/QueueManager.swift

@@ -7,7 +7,7 @@
 
 import Foundation
 
-protocol QueueManagerDelegate: class {
+protocol QueueManagerDelegate: AnyObject {
     func onReceivedFirstItem()
     func onCurrentIndexChanged(oldIndex: Int, newIndex: Int)
 }

SwiftAudioEx/Classes/QueuedAudioPlayer.swift

@@ -11,10 +11,15 @@ import MediaPlayer
 /**
  An audio player that can keep track of a queue of AudioItems.
  */
-public class QueuedAudioPlayer: AudioPlayer {
+public class QueuedAudioPlayer: AudioPlayer, QueueManagerDelegate {
 
     let queueManager: QueueManager = QueueManager<AudioItem>()
 
+    public init() {
+        super.init()
+        queueManager.delegate = self
+    }
+
     /// The repeat mode for the queue player.
     public var repeatMode: RepeatMode = .off
 
@@ -34,6 +39,7 @@ public class QueuedAudioPlayer: AudioPlayer {
      */
     public override func stop() {
         super.stop()
+        self.event.queueIndex.emit(data: (currentIndex, nil))
     }
 
     override func reset() {
@@ -199,4 +205,16 @@ public class QueuedAudioPlayer: AudioPlayer {
             } catch { /* TODO: handle possible errors from load */ }
         }
     }
+
+    // MARK: - QueueManagerDelegate
+
+    func onCurrentIndexChanged(oldIndex: Int, newIndex: Int) {
+        // if _currentItem is nil, then this was triggered by a reset. ignore.
+        if _currentItem == nil { return }
+        self.event.queueIndex.emit(data: (oldIndex, newIndex))
+    }
+
+    func onReceivedFirstItem() {
+        self.event.queueIndex.emit(data: (nil, 0))
+    }
 }