Fix UWP volume, mediasource exception, android position (#9452)

* Fix UWP volume, mediasource exception, android position

* - unsubscribe from events

* - null check

Xamarin.Forms.Controls/GalleryPages/MediaElementDemoPage.cs

@@ -93,6 +93,15 @@ namespace Xamarin.Forms.Controls
 			aspectStack.Children.Add(aspectFillButton);
 			aspectStack.Children.Add(fillButton);
 
+			var volumeSlider = new Slider()
+			{
+				Minimum = 0,
+				Maximum = 1
+			};
+			volumeSlider.Value = 0.1;
+
+			volumeSlider.ValueChanged += VolumeSlider_ValueChanged;
+
 			var stack = new StackLayout();
 			stack.Padding = new Thickness(10);
 			stack.Spacing = 10;
@@ -104,9 +113,17 @@ namespace Xamarin.Forms.Controls
 			stack.Children.Add(mediaControlStack);
 			stack.Children.Add(aspectStack);
 			stack.Children.Add(consoleLabel);
+			stack.Children.Add(new Label() { Text = "Volume:" });
+			stack.Children.Add(volumeSlider);
+			element.Volume = 0.1;
 			Content = stack;	
 		}
 
+		private void VolumeSlider_ValueChanged(object sender, ValueChangedEventArgs e)
+		{
+			element.Volume = (sender as Slider).Value;
+		}
+
 		void Element_MediaOpened(object sender, EventArgs e)
 		{
 			consoleLabel.Text += "Media opened" + Environment.NewLine;

Xamarin.Forms.Platform.Android/FastRenderers/MediaElementRenderer.cs

@@ -70,6 +70,18 @@ namespace Xamarin.Forms.Platform.Android
 			ViewRenderer.MeasureExactly(this, Element, Context);
 		}
 
+		void UnsubscribeFromEvents(MediaElement element)
+		{
+			if (element == null)
+				return;
+
+			element.PropertyChanged -= OnElementPropertyChanged;
+			element.SeekRequested -= SeekRequested;
+			element.StateRequested -= StateRequested;
+			element.PositionRequested -= OnPositionRequested;
+
+		}
+
 		void IVisualElementRenderer.SetElement(VisualElement element)
 		{
 			if (element is null)
@@ -85,9 +97,7 @@ namespace Xamarin.Forms.Platform.Android
 
 			if (oldElement != null)
 			{
-				oldElement.PropertyChanged -= OnElementPropertyChanged;
-				oldElement.SeekRequested -= SeekRequested;
-				oldElement.StateRequested -= StateRequested;
+				UnsubscribeFromEvents(oldElement);
 			}
 
 			Color currentColor = oldElement?.BackgroundColor ?? Color.Default;
@@ -96,9 +106,13 @@ namespace Xamarin.Forms.Platform.Android
 				UpdateBackgroundColor();
 			}
 
-			MediaElement.PropertyChanged += OnElementPropertyChanged;
-			MediaElement.SeekRequested += SeekRequested;
-			MediaElement.StateRequested += StateRequested;
+			if (MediaElement != null)
+			{
+				MediaElement.PropertyChanged += OnElementPropertyChanged;
+				MediaElement.SeekRequested += SeekRequested;
+				MediaElement.StateRequested += StateRequested;
+				MediaElement.PositionRequested += OnPositionRequested;
+			}
 
 			if (_tracker is null)
 			{
@@ -115,6 +129,9 @@ namespace Xamarin.Forms.Platform.Android
 
 		void StateRequested(object sender, StateRequested e)
 		{
+			if (_view == null)
+				return;
+
 			switch (e.State)
 			{
 				case MediaElementState.Playing:
@@ -142,8 +159,19 @@ namespace Xamarin.Forms.Platform.Android
 			Controller.Position = _view.Position;
 		}
 
+		void OnPositionRequested(object sender, EventArgs e)
+		{
+			if (_view == null)
+				return;
+
+			Controller.Position = _view.Position;
+		}
+
 		void SeekRequested(object sender, SeekRequested e)
 		{
+			if (_view == null)
+				return;
+
 			Controller.Position = _view.Position;
 		}
 
@@ -190,7 +218,7 @@ namespace Xamarin.Forms.Platform.Android
 
 				if (Element != null)
 				{
-					Element.PropertyChanged -= OnElementPropertyChanged;
+					UnsubscribeFromEvents(Element as MediaElement);
 
 					if (Platform.GetRenderer(Element) == this)
 						Element.ClearValue(Platform.RendererProperty);
@@ -226,6 +254,9 @@ namespace Xamarin.Forms.Platform.Android
 
 		void MetadataRetrieved(object sender, EventArgs e)
 		{
+			if (_view == null)
+				return;
+
 			Controller.Duration = _view.DurationTimeSpan;
 			Controller.VideoHeight = _view.VideoHeight;
 			Controller.VideoWidth = _view.VideoWidth;
@@ -276,22 +307,34 @@ namespace Xamarin.Forms.Platform.Android
 
 		void UpdateKeepScreenOn()
 		{
+			if (_view == null)
+				return;
+
 			_view.KeepScreenOn = MediaElement.KeepScreenOn;
 		}
 
 		void UpdateShowPlaybackControls()
 		{
+			if (_controller == null)
+				return;
+
 			_controller.Visibility = MediaElement.ShowsPlaybackControls ? ViewStates.Visible : ViewStates.Gone;
 		}
 
 		void UpdateSource()
 		{
+			if (_view == null)
+				return;
+
 			if (MediaElement.Source != null)
 			{
 				if (MediaElement.Source is UriMediaSource uriSource)
 				{
 					if (uriSource.Uri.Scheme == "ms-appx")
 					{
+						if (uriSource.Uri.LocalPath.Length <= 1)
+							return;
+
 						// video resources should be in the raw folder with Build Action set to AndroidResource
 						string uri = "android.resource://" + Context.PackageName + "/raw/" + uriSource.Uri.LocalPath.Substring(1, uriSource.Uri.LocalPath.LastIndexOf('.') - 1).ToLower();
 						_view.SetVideoURI(global::Android.Net.Uri.Parse(uri));
@@ -339,12 +382,18 @@ namespace Xamarin.Forms.Platform.Android
 
 		void MediaPlayer.IOnCompletionListener.OnCompletion(MediaPlayer mp)
 		{
+			if (Controller == null)
+				return;
+
 			Controller.Position = TimeSpan.FromMilliseconds(_mediaPlayer.CurrentPosition);
 			Controller.OnMediaEnded();
 		}
 
 		void MediaPlayer.IOnPreparedListener.OnPrepared(MediaPlayer mp)
 		{
+			if (Controller == null)
+				return;
+
 			Controller.OnMediaOpened();
 
 			UpdateLayoutParameters();
@@ -366,6 +415,9 @@ namespace Xamarin.Forms.Platform.Android
 
 		void UpdateLayoutParameters()
 		{
+			if (_view == null)
+				return;
+
 			if (_view.VideoWidth == 0 || _view.VideoHeight == 0)
 			{
 				_view.LayoutParameters = new FrameLayout.LayoutParams(Width, Height, GravityFlags.Fill);
@@ -442,13 +494,18 @@ namespace Xamarin.Forms.Platform.Android
 
 		bool MediaPlayer.IOnErrorListener.OnError(MediaPlayer mp, MediaError what, int extra)
 		{
+			if (Controller == null)
+				return false;
+
 			Controller.OnMediaFailed();
 			return false;
 		}
 		
 		bool MediaPlayer.IOnInfoListener.OnInfo(MediaPlayer mp, MediaInfo what, int extra)
 		{
-			System.Diagnostics.Debug.WriteLine(what);
+			if (_view == null)
+				return false;
+
 			switch (what)
 			{
 				case MediaInfo.BufferingStart:

Xamarin.Forms.Platform.UAP/MediaElementRenderer.cs

@@ -152,6 +152,8 @@ namespace Xamarin.Forms.Platform.UWP
 			Controller.Duration = Control.NaturalDuration.HasTimeSpan ? Control.NaturalDuration.TimeSpan : (TimeSpan?)null;
 			Controller.VideoHeight = Control.NaturalVideoHeight;
 			Controller.VideoWidth = Control.NaturalVideoWidth;
+			Control.Volume = Element.Volume;
+			Control.Stretch = Element.Aspect.ToStretch();
 
 			Controller.OnMediaOpened();
 		}

Xamarin.Forms.Platform.iOS/Renderers/MediaElementRenderer.cs

@@ -56,6 +56,9 @@ namespace Xamarin.Forms.Platform.iOS
 				{
 					if (uriSource.Uri.Scheme == "ms-appx")
 					{
+						if (uriSource.Uri.LocalPath.Length <= 1)
+							return;
+
 						// used for a file embedded in the application package
 						asset = AVAsset.FromUrl(NSUrl.FromFilename(uriSource.Uri.LocalPath.Substring(1)));
 					}