Merge pull request #12211 from ajpinedam/ajpm/fix.android.scroll.offset

fix(ScrollView): Android FastScrolling wrong Offsets

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Controls/Given_ScrollViewer.cs

@@ -459,6 +459,68 @@ public async Task When_NonRound_Content_Height()
 			Assert.AreEqual(outerScrollViewer.ExtentHeight, outerScrollViewer.ViewportHeight, 0.000001);
 		}
 
+		[TestMethod]
+		[RunsOnUIThread]
+		[RequiresFullWindow]
+#if __MACOS__
+		[Ignore("Currently fails on macOS, part of #9282! epic")]
+#endif
+		public async Task When_ChangeView_Offset()
+		{
+			const double offset = 100;
+
+			var scroll = new ScrollViewer()
+			{
+				Background = new SolidColorBrush(Colors.Yellow)
+			};
+
+			var stackPanel = new StackPanel()
+			{
+				Orientation = Orientation.Vertical,
+				Height = 5000,
+			};
+
+			stackPanel.Children.Add(new Border() { Height = 200 });
+
+			var target = new Border()
+			{
+				Background = new SolidColorBrush(Colors.Lime),
+				Height = 50,
+			};
+
+			stackPanel.Children.Add(target);
+
+			var scrollChanged = false;
+			scroll.ViewChanged += (s, e) =>
+			{
+				scrollChanged = true;
+			};
+
+			scroll.Content = stackPanel;
+
+			try
+			{
+
+				var container = new Border() { Child = scroll };
+
+				WindowHelper.WindowContent = container;
+
+				await WindowHelper.WaitForLoaded(scroll);
+
+				_ = scroll.ChangeView(null, offset, null, true);
+
+				await WindowHelper.WaitFor(() => scrollChanged);
+
+				var loc = target.TransformToVisual(scroll).TransformPoint(new Point(0, 0));
+				Assert.AreEqual(offset, loc.Y);
+			}
+			finally
+			{
+				WindowHelper.WindowContent = null;
+			}
+		}
+
+
 #if __ANDROID__
 		[TestMethod]
 		[RunsOnUIThread]

src/Uno.UI/UI/Xaml/Controls/ScrollContentPresenter/ScrollContentPresenter.Native.cs

@@ -115,9 +115,10 @@ public double ExtentWidth
 		#region Native SCP to SCP
 		internal void OnNativeScroll(double horizontalOffset, double verticalOffset, bool isIntermediate)
 		{
+			ScrollOffsets = new Point(horizontalOffset, verticalOffset);
+
 			Scroller?.OnPresenterScrolled(horizontalOffset, verticalOffset, isIntermediate);
 
-			ScrollOffsets = new Point(horizontalOffset, verticalOffset);
 			InvalidateViewport();
 		}