[Android] ScrollView should send correct ScrollX and ScrollY (#394)

* Android should show correct ScrollX and ScrollY when scrolling in both directions

* Adding sample code to demonstrate scrolling

* Orientation fix

* ScrollTo should work for horizontal + vertical scrolling

* Get correct scroll x and y values for ScrollOrientation.Both

* Convert positions to pixels

* Adding unit test to watch out for incorrect animation positioning

* automated test

* improvements

* fixed texts

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Bugzilla41415.cs

@@ -0,0 +1,115 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Bugzilla, 41415, "ScrollX and ScrollY values are not consistent with iOS", PlatformAffected.Android)]
+	public class Bugzilla41415 : TestContentPage
+	{
+		const string ButtonText = "Click Me";
+		float _x, _y;
+		bool _didXChange, _didYChange;
+
+		protected override void Init()
+		{
+			var grid = new Grid
+			{
+				BackgroundColor = Color.Yellow,
+				WidthRequest = 1000,
+				HeightRequest = 1000,
+				Children =
+				{
+					new BoxView
+					{
+						WidthRequest =  200,
+						HeightRequest = 200,
+						BackgroundColor = Color.Red,
+						HorizontalOptions = LayoutOptions.Center,
+						VerticalOptions = LayoutOptions.Center
+					}
+				}
+			};
+
+			var labelx = new Label();
+			var labely = new Label();
+			var labelz = new Label();
+			var labela = new Label();
+
+			var scrollView = new ScrollView
+			{
+				Orientation = ScrollOrientation.Both,
+				HorizontalOptions = LayoutOptions.FillAndExpand,
+				VerticalOptions = LayoutOptions.FillAndExpand
+			};
+
+			scrollView.Content = grid;
+			scrollView.Scrolled += (sender, args) =>
+			{
+				labelx.Text = $"x: {args.ScrollX}";
+				labely.Text = $"y: {args.ScrollY}";
+
+				// first and second taps
+				if (_x == 0)
+				{
+					if (args.ScrollX != 0 && args.ScrollX != 100)
+						_didXChange = true;
+					if (args.ScrollY != 0 && args.ScrollY != 100)
+						_didYChange = true;
+				}
+				else if (_x == 100)
+				{
+					if (args.ScrollX != _x && args.ScrollX != _x + 100)
+						_didXChange = true;
+					if (args.ScrollY != 100)
+						_didYChange = true;
+				}
+
+				labelz.Text = "z: " + _didXChange.ToString();
+				labela.Text = "a: " + _didYChange.ToString();
+			};
+
+			var button = new Button { Text = ButtonText };
+			button.Clicked += async (sender, e) =>
+			{
+				// reset
+				labelx.Text = null;
+				labely.Text = null;
+				labelz.Text = null;
+				labela.Text = null;
+				_didXChange = false;
+				_didYChange = false;
+
+				await scrollView.ScrollToAsync(_x + 100, _y + 100, true);
+				_x = 100;
+			};
+
+			Content = new StackLayout { Children = { button, labelx, labely, labelz, labela, scrollView } };
+		}
+
+#if UITEST
+
+		[Test]
+		public void Bugzilla41415Test()
+		{
+			RunningApp.WaitForElement(q => q.Marked(ButtonText));
+			RunningApp.Tap(q => q.Marked(ButtonText));
+			RunningApp.WaitForElement(q => q.Marked("x: 100"));
+			RunningApp.WaitForElement(q => q.Marked("y: 100"));
+			RunningApp.WaitForElement(q => q.Marked("z: True"));
+			RunningApp.WaitForElement(q => q.Marked("a: True"));
+			RunningApp.Tap(q => q.Marked(ButtonText));
+			RunningApp.WaitForElement(q => q.Marked("x: 200"));
+			RunningApp.WaitForElement(q => q.Marked("y: 100"));
+			RunningApp.WaitForElement(q => q.Marked("z: True"));
+			RunningApp.WaitForElement(q => q.Marked("a: False"));
+		}
+
+#endif
+	}
+}

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

@@ -115,6 +115,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41078.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla40998.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41205.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41415.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41418.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla41424.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Bugzilla42069.cs" />

Xamarin.Forms.Core.UnitTests/ScrollViewUnitTests.cs

@@ -453,5 +453,36 @@ namespace Xamarin.Forms.Core.UnitTests
 			Assert.AreEqual(100, scroll.Height);
 			Assert.AreEqual(100, scroll.Width);
 		}
+
+		[Test]
+		public void TestBackToBackBiDirectionalScroll()
+		{
+			var scrollView = new ScrollView
+			{
+				Orientation = ScrollOrientation.Both,
+				Platform = new UnitPlatform(),
+				Content = new Grid
+				{
+					WidthRequest = 1000,
+					HeightRequest = 1000
+				}
+			};
+
+			var y100Count = 0;
+
+			((IScrollViewController)scrollView).ScrollToRequested += (sender, args) =>
+			{
+				if (args.ScrollY == 100)
+				{
+					++y100Count;
+				}
+			};
+
+			scrollView.ScrollToAsync(100, 100, true);
+			Assert.AreEqual(y100Count, 1);
+
+			scrollView.ScrollToAsync(0, 100, true);
+			Assert.AreEqual(y100Count, 2);
+		}
 	}
 }

Xamarin.Forms.Platform.Android/Renderers/ScrollViewRenderer.cs

@@ -202,7 +202,18 @@ namespace Xamarin.Forms.Platform.Android
 		internal void UpdateScrollPosition(double x, double y)
 		{
 			if (_view != null)
+			{
+				if (_view.Orientation == ScrollOrientation.Both)
+				{
+					if (x == 0)
+						x = Forms.Context.FromPixels(_hScrollView.ScrollX);
+
+					if (y == 0)
+						y = Forms.Context.FromPixels(ScrollY);
+				}
+
 				Controller.SetScrolledPosition(x, y);
+			}
 		}
 
 		static int GetDistance(double start, double position, double v)
@@ -248,8 +259,8 @@ namespace Xamarin.Forms.Platform.Android
 
 			var x = (int)Forms.Context.ToPixels(e.ScrollX);
 			var y = (int)Forms.Context.ToPixels(e.ScrollY);
-			int currentX = _view.Orientation == ScrollOrientation.Horizontal ? _hScrollView.ScrollX : ScrollX;
-			int currentY = _view.Orientation == ScrollOrientation.Horizontal ? _hScrollView.ScrollY : ScrollY;
+			int currentX = _view.Orientation == ScrollOrientation.Horizontal || _view.Orientation == ScrollOrientation.Both ? _hScrollView.ScrollX : ScrollX;
+			int currentY = _view.Orientation == ScrollOrientation.Vertical || _view.Orientation == ScrollOrientation.Both ? ScrollY : _hScrollView.ScrollY;
 			if (e.Mode == ScrollToMode.Element)
 			{
 				Point itemPosition = Controller.GetScrollPositionForElement(e.Element as VisualElement, e.Position);
@@ -275,10 +286,19 @@ namespace Xamarin.Forms.Platform.Android
 						return;
 					}
 
-					if (_view.Orientation == ScrollOrientation.Horizontal)
-						_hScrollView.ScrollTo(distX, distY);
-					else
-						ScrollTo(distX, distY);
+					switch (_view.Orientation)
+					{
+						case ScrollOrientation.Horizontal:
+							_hScrollView.ScrollTo(distX, distY);
+							break;
+						case ScrollOrientation.Vertical:
+							ScrollTo(distX, distY);
+							break;
+						default:
+							_hScrollView.ScrollTo(distX, distY);
+							ScrollTo(distX, distY);
+							break;
+					}
 				};
 				animator.AnimationEnd += delegate
 				{
@@ -291,10 +311,19 @@ namespace Xamarin.Forms.Platform.Android
 			}
 			else
 			{
-				if (_view.Orientation == ScrollOrientation.Horizontal)
-					_hScrollView.ScrollTo(x, y);
-				else
-					ScrollTo(x, y);
+				switch (_view.Orientation)
+				{
+					case ScrollOrientation.Horizontal:
+						_hScrollView.ScrollTo(x, y);
+						break;
+					case ScrollOrientation.Vertical:
+						ScrollTo(x, y);
+						break;
+					default:
+						_hScrollView.ScrollTo(x, y);
+						ScrollTo(x, y);
+						break;
+				}
 				Controller.SendScrollFinished();
 			}
 		}