[A] PanGestureRecognizer will consistently send Completed event (#313)

* Adjust gallery page for reproduction

* [A] Forward OnTouchEvent to Listener...

...and end scrolling on Up.

Xamarin.Forms.Controls/ControlGalleryPages/PanGestureGalleryPage.cs

@@ -8,33 +8,54 @@ namespace Xamarin.Forms.Controls
 {
 	public class PanGestureGalleryPage : ContentPage
 	{
+		public class PanCompleteArgs : EventArgs
+		{
+			public PanCompleteArgs(string message) { Message = message; }
+			public string Message
+			{
+				get; private set;
+			}
+		}
+
 		public class PanContainer : ContentView
 		{
-			public PanContainer ()
+			double _x, _y;
+			double _currentScale = 1;
+
+			public EventHandler<PanCompleteArgs> PanCompleted;
+
+			public PanContainer()
 			{
-				var pan = new PanGestureRecognizer
+				GestureRecognizers.Add(GetPinch());
+				GestureRecognizers.Add(GetPan());
+			}
+
+			PanGestureRecognizer GetPan()
+			{
+				var pan = new PanGestureRecognizer();
+				pan.PanUpdated += (s, e) =>
 				{
-					TouchPoints = 1
-				};
-
-				pan.PanUpdated += (object s, PanUpdatedEventArgs e) =>
-				{
-					switch (e.StatusType) {
-
-						case GestureStatus.Started: break;
-
+					switch (e.StatusType)
+					{
 						case GestureStatus.Running:
 							Content.TranslationX = e.TotalX;
 							Content.TranslationY = e.TotalY;
 							break;
 
-						default:
-							Content.TranslationX = Content.TranslationY = 0;
+						case GestureStatus.Completed:
+							_x = Content.TranslationX;
+							_y = Content.TranslationY;
+
+							PanCompleted?.Invoke(s, new PanCompleteArgs($"x: {_x}, y: {_y}"));
 							break;
 					}
 				};
+				return pan;
+			}
 
-				var pinch = new PinchGestureRecognizer ();
+			PinchGestureRecognizer GetPinch()
+			{
+				var pinch = new PinchGestureRecognizer();
 
 				double xOffset = 0;
 				double yOffset = 0;
@@ -43,14 +64,16 @@ namespace Xamarin.Forms.Controls
 				pinch.PinchUpdated += (sender, e) =>
 				{
 
-					if (e.Status == GestureStatus.Started) {
+					if (e.Status == GestureStatus.Started)
+					{
 						startScale = Content.Scale;
 						Content.AnchorX = Content.AnchorY = 0;
 					}
-					if (e.Status == GestureStatus.Running) {
 
+					if (e.Status == GestureStatus.Running)
+					{
 						_currentScale += (e.Scale - 1) * startScale;
-						_currentScale = Math.Max (1, _currentScale);
+						_currentScale = Math.Max(1, _currentScale);
 
 						var renderedX = Content.X + xOffset;
 						var deltaX = renderedX / Width;
@@ -65,32 +88,42 @@ namespace Xamarin.Forms.Controls
 						double targetX = xOffset - (originX * Content.Width) * (_currentScale - startScale);
 						double targetY = yOffset - (originY * Content.Height) * (_currentScale - startScale);
 
-						Content.TranslationX = targetX.Clamp (-Content.Width * (_currentScale - 1), 0);
-						Content.TranslationY = targetY.Clamp (-Content.Height * (_currentScale - 1), 0);
+						Content.TranslationX = targetX.Clamp(-Content.Width * (_currentScale - 1), 0);
+						Content.TranslationY = targetY.Clamp(-Content.Height * (_currentScale - 1), 0);
 
 						Content.Scale = _currentScale;
 					}
-					if (e.Status == GestureStatus.Completed) {
+
+					if (e.Status == GestureStatus.Completed)
+					{
 						xOffset = Content.TranslationX;
 						yOffset = Content.TranslationY;
 					}
 				};
-
-				GestureRecognizers.Add (pinch);
-
-				GestureRecognizers.Add (pan);
+				return pinch;
 			}
-
-			double _currentScale = 1;
 		}
 
-		public PanGestureGalleryPage ()
+		public PanGestureGalleryPage()
 		{
-			var image = new Image { Source = "http://placehold.it/2000x2000", BackgroundColor = Color.Gray, WidthRequest = 2000, HeightRequest = 2000, VerticalOptions = LayoutOptions.Center, HorizontalOptions = LayoutOptions.Center };
+			var box = new Image
+			{
+				BackgroundColor = Color.Gray,
+				WidthRequest = 2000,
+				HeightRequest = 2000,
+				VerticalOptions = LayoutOptions.Center,
+				HorizontalOptions = LayoutOptions.Center
+			};
 
-			var panme = new PanContainer { Content = image };
+			var label = new Label { Text = "Use two fingers to pinch. Use one finger to pan." };
 
-			Content = new StackLayout { Children = { new Label { Text = "Use two fingers to pinch. Use one finger to pan." }, panme }, Padding = new Thickness (20) };
+			var panme = new PanContainer { Content = box };
+			panme.PanCompleted += (s, e) =>
+			{
+				label.Text = e.Message;
+			};
+
+			Content = new StackLayout { Children = { label, panme }, Padding = new Thickness(20) };
 		}
 	}
 }

Xamarin.Forms.Platform.Android/InnerGestureListener.cs

@@ -38,12 +38,18 @@ namespace Xamarin.Forms.Platform.Android
 		}
 
 		// This is needed because GestureRecognizer callbacks can be delayed several hundred milliseconds
-		// which can result in the need to resurect this object if it has already been disposed. We dispose
+		// which can result in the need to resurrect this object if it has already been disposed. We dispose
 		// eagerly to allow easier garbage collection of the renderer
 		internal InnerGestureListener(IntPtr handle, JniHandleOwnership ownership) : base(handle, ownership)
 		{
 		}
 
+		internal void OnTouchEvent(MotionEvent e)
+		{
+			if (e.Action == MotionEventActions.Up)
+				EndScrolling();
+		}
+
 		bool GestureDetector.IOnDoubleTapListener.OnDoubleTap(MotionEvent e)
 		{
 			if (_tapDelegate == null || _tapGestureRecognizers == null)

Xamarin.Forms.Platform.Android/VisualElementRenderer.cs

@@ -98,6 +98,9 @@ namespace Xamarin.Forms.Platform.Android
 					ScaleGestureDetectorCompat.SetQuickScaleEnabled(_scaleDetector.Value, true);
 				handled = _scaleDetector.Value.OnTouchEvent(e);
 			}
+
+			_gestureListener?.OnTouchEvent(e);
+
 			return _gestureDetector.Value.OnTouchEvent(e) || handled;
 		}