Implemented MediaElement ObjectDisposedException fix (#1870)

Implemented fix

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/MediaElement/Android/FormsVideoView.android.cs

@@ -52,10 +52,14 @@ protected void ExtractMetadata(MediaMetadataRetriever retriever)
 
  public override async void SetVideoURI(global::Android.Net.Uri? uri, IDictionary<string, string>? headers)
  {
+ base.SetVideoURI(uri, headers);
+
+ // this instance could get disposed during awaiting, so a call to the base method (AFTER awaiting)
+ // would throw ObjectDisposedException and be impossible to catch due to async void
  if (uri != null)
+ {
  await SetMetadata(uri, headers);
-
- base.SetVideoURI(uri, headers);
+ }
  }
 
  protected async Task SetMetadata(global::Android.Net.Uri uri, IDictionary<string, string>? headers)

src/CommunityToolkit/Xamarin.CommunityToolkit/Views/MediaElement/Android/MediaElementRenderer.android.cs

@@ -21,7 +21,7 @@ public class MediaElementRenderer : FrameLayout, IVisualElementRenderer, IViewRe
  VisualElementTracker? tracker;
  protected MediaController? controller;
  protected MediaPlayer? mediaPlayer;
- protected FormsVideoView view;
+ protected FormsVideoView? view;
  bool isDisposed;
  int? defaultLabelFor;
 
@@ -47,9 +47,14 @@ public MediaElementRenderer(Context context)
 
  public override float Alpha
  {
- get => view.Alpha;
+ get => view?.Alpha ?? throw new ObjectDisposedException(typeof(FormsVideoView).FullName);
  set
  {
+ if (view == null)
+ {
+ throw new ObjectDisposedException(typeof(FormsVideoView).FullName);
+ }
+
  // VideoView opens a separate Window above the current one.
  // This is because it is based on the SurfaceView.
  // And we cannot set alpha or perform animations with it because it is not synchronized with your other UI elements.
@@ -509,6 +514,7 @@ protected virtual void ReleaseControl()
  view.SetOnPreparedListener(null);
  view.SetOnCompletionListener(null);
  view.Dispose();
+ view = null;
  }
 
  if (controller != null)