Give layouts a chance to handle touch events after passing though immediate children (#902)

* Repro for Bugzilla 55912

* Automate test

* Give the layout a chance to actually handle gestures before bubbling up

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla55912.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Diagnostics;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+#if UITEST
+using NUnit.Framework;
+
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 955912, "Tap event not always propagated to containing Grid/StackLayout",
+		PlatformAffected.Android)]
+	public class Bugzilla55912 : TestContentPage
+	{
+		const string Success = "Success";
+		const string GridLabelId = "GridLabel";
+		const string StackLabelId = "StackLabel";
+
+		protected override void Init()
+		{
+			var layout = new Grid();
+
+			layout.RowDefinitions.Add(new RowDefinition { Height = GridLength.Star });
+			layout.RowDefinitions.Add(new RowDefinition { Height = GridLength.Star });
+			layout.RowDefinitions.Add(new RowDefinition { Height = GridLength.Star });
+
+			var testGrid = new Grid { BackgroundColor = Color.Red };
+			var gridLabel = new Label
+			{
+				AutomationId = GridLabelId,
+				Text = "This is a Grid with a TapGesture",
+				FontSize = 24,
+				BackgroundColor = Color.Green
+			};
+			Grid.SetRow(testGrid, 1);
+			testGrid.Children.Add(gridLabel);
+
+			var testStack = new StackLayout { BackgroundColor = Color.Default };
+			var stackLabel = new Label
+			{
+				AutomationId = StackLabelId,
+				Text = "This StackLayout also has a TapGesture",
+				FontSize = 24,
+				BackgroundColor = Color.Green
+			};
+			Grid.SetRow(testStack, 2);
+			testStack.Children.Add(stackLabel);
+
+			layout.Children.Add(testGrid);
+			layout.Children.Add(testStack);
+
+			Content = layout;
+
+			testGrid.GestureRecognizers.Add(new TapGestureRecognizer
+			{
+				NumberOfTapsRequired = 1,
+				Command = new Command(() =>
+				{
+					Debug.WriteLine($"***** TestGrid Tapped: {DateTime.Now} *****");
+					layout.Children.Add(new Label { AutomationId = Success, Text = Success });
+				})
+			});
+
+			testStack.GestureRecognizers.Add(new TapGestureRecognizer
+			{
+				NumberOfTapsRequired = 1,
+				Command = new Command(() =>
+				{
+					Debug.WriteLine($"***** TestStack Tapped: {DateTime.Now} *****");
+					layout.Children.Add(new Label { AutomationId = Success, Text = Success });
+				})
+			});
+		}
+
+#if UITEST
+		[Test]
+		public void GestureBubblingInStackLayout()
+		{
+			RunningApp.WaitForElement(StackLabelId);
+			RunningApp.Tap(StackLabelId);
+			RunningApp.WaitForElement(Success);
+		}
+
+		[Test]
+		public void GestureBubblingInGrid()
+		{
+			RunningApp.WaitForElement(GridLabelId);
+			RunningApp.Tap(GridLabelId);
+			RunningApp.WaitForElement(Success);
+		}
+#endif
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -196,6 +196,7 @@
     </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla52266.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla53445.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla55912.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CarouselAsync.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34561.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla34727.cs" />

Xamarin.Forms.Platform.Android/Platform.cs

@@ -1070,9 +1070,12 @@ namespace Xamarin.Forms.Platform.Android
 
 				if (result && _notReallyHandled)
 				{
-					// If the child control returned true from its touch event handler but signalled that it was a fake "true", leave the event unhandled
-					// so parent controls have the opportunity
-					return false;
+					// If the child control returned true from its touch event handler but signalled that it was a fake "true", then we
+					// don't consider the event truly "handled" yet. 
+					// Since a child control short-circuited the normal dispatchTouchEvent stuff, this layout never got the chance for
+					// IOnTouchListener.OnTouch and the OnTouchEvent override to try handling the touches; we'll do that now
+
+					return OnTouchEvent(e);
 				}
 
 				return result;