Ensured that observers are added only once (#928)

* Ensured that observers are added only once

* renamed item to playerItem according to @pictos suggestion

Co-authored-by: Gerald Versluis <[email protected]>

Author: Huaba93

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/MediaElement/iOS/MediaElementRenderer.ios.cs

@@ -26,9 +26,9 @@ public class MediaElementRenderer : ViewRenderer<ToolKitMediaElement, UIView>
 		protected IDisposable rateObserver;
 		protected IDisposable volumeObserver;
 		bool idleTimerDisabled = false;
+		AVPlayerItem playerItem;
 
-		public MediaElementRenderer() =>
-			playedToEndObserver = NSNotificationCenter.DefaultCenter.AddObserver(AVPlayerItem.DidPlayToEndTimeNotification, PlayedToEnd);
+		public MediaElementRenderer() => AddPlayedToEndObserver();
 
 		protected virtual void SetKeepScreenOn(bool value)
 		{
@@ -81,18 +81,16 @@ protected virtual void UpdateSource()
 						asset = AVAsset.FromUrl(NSUrl.FromFilename(fileSource.File));
 				}
 
-				var item = new AVPlayerItem(asset);
-				DisposeObservers(ref statusObserver);
-
-				statusObserver = item.AddObserver("status", NSKeyValueObservingOptions.New, ObserveStatus);
+				playerItem = new AVPlayerItem(asset);
+				AddStatusObserver();
 
 				if (avPlayerViewController.Player != null)
-					avPlayerViewController.Player.ReplaceCurrentItemWithPlayerItem(item);
+					avPlayerViewController.Player.ReplaceCurrentItemWithPlayerItem(playerItem);
 				else
 				{
-					avPlayerViewController.Player = new AVPlayer(item);
-					rateObserver = avPlayerViewController.Player.AddObserver("rate", NSKeyValueObservingOptions.New, ObserveRate);
-					volumeObserver = avPlayerViewController.Player.AddObserver("volume", NSKeyValueObservingOptions.New, ObserveVolume);
+					avPlayerViewController.Player = new AVPlayer(playerItem);
+					AddRateObserver();
+					AddVolumeObserver();
 				}
 
 				UpdateVolume();
@@ -104,7 +102,7 @@ protected virtual void UpdateSource()
 			{
 				avPlayerViewController.Player?.Pause();
 				avPlayerViewController.Player?.ReplaceCurrentItemWithPlayerItem(null);
-				DisposeObservers(ref statusObserver);
+				DestroyStatusObserver();
 				Controller.CurrentState = MediaElementState.Stopped;
 			}
 		}
@@ -380,13 +378,10 @@ protected override void OnElementChanged(ElementChangedEventArgs<MediaElement> e
 					AVAudioSession.SharedInstance().SetActive(false);
 				}
 
-				if (playedToEndObserver != null)
-					NSNotificationCenter.DefaultCenter.RemoveObserver(playedToEndObserver);
-
-				DisposeObservers(ref playedToEndObserver);
-				DisposeObservers(ref rateObserver);
-				DisposeObservers(ref volumeObserver);
-				DisposeObservers(ref statusObserver);
+				DestroyPlayedToEndObserver();
+				DestroyRateObserver();
+				DestroyVolumeObserver();
+				DestroyStatusObserver();
 			}
 
 			if (e.NewElement != null)
@@ -404,7 +399,7 @@ protected override void OnElementChanged(ElementChangedEventArgs<MediaElement> e
 				if (Element.KeepScreenOn)
 					SetKeepScreenOn(true);
 
-				playedToEndObserver = NSNotificationCenter.DefaultCenter.AddObserver(AVPlayerItem.DidPlayToEndTimeNotification, PlayedToEnd);
+				AddPlayedToEndObserver();
 
 				UpdateBackgroundColor();
 				UpdateSource();
@@ -424,5 +419,49 @@ protected void DisposeObservers(ref NSObject disposable)
 			disposable?.Dispose();
 			disposable = null;
 		}
+
+		void AddVolumeObserver()
+		{
+			DestroyVolumeObserver();
+			volumeObserver = avPlayerViewController.Player?.AddObserver("volume", NSKeyValueObservingOptions.New,
+					ObserveVolume);
+		}
+
+		void AddRateObserver()
+		{
+			DestroyRateObserver();
+			rateObserver = avPlayerViewController.Player?.AddObserver("rate", NSKeyValueObservingOptions.New,
+					ObserveRate);
+		}
+
+		void AddStatusObserver()
+		{
+			DestroyStatusObserver();
+			statusObserver = playerItem.AddObserver("status", NSKeyValueObservingOptions.New, ObserveStatus);
+		}
+
+		void AddPlayedToEndObserver()
+		{
+			DestroyPlayedToEndObserver();
+			playedToEndObserver =
+				NSNotificationCenter.DefaultCenter.AddObserver(AVPlayerItem.DidPlayToEndTimeNotification, PlayedToEnd);
+		}
+
+		void DestroyVolumeObserver() => DisposeObservers(ref volumeObserver);
+
+		void DestroyRateObserver() => DisposeObservers(ref rateObserver);
+
+		void DestroyStatusObserver() => DisposeObservers(ref statusObserver);
+
+		void DestroyPlayedToEndObserver()
+		{
+			if (playedToEndObserver == null)
+			{
+				return;
+			}
+
+			NSNotificationCenter.DefaultCenter.RemoveObserver(playedToEndObserver);
+			DisposeObservers(ref playedToEndObserver);
+		}
 	}
 }