Fix Android ScrollView to Measure Content Correct

Co-authored-by: kubaflo <42434498+kubaflo@users.noreply.github.com>

Author: PureWeen

src/Controls/src/Core/ScrollView/ScrollView.cs

@@ -515,7 +515,8 @@ Size ICrossPlatformLayout.CrossPlatformArrange(Rect bounds)
 			return bounds.Size;
 		}
 
-		Size IContentView.CrossPlatformMeasure(double widthConstraint, double heightConstraint) => ((ICrossPlatformLayout)this).CrossPlatformMeasure(widthConstraint, heightConstraint);
+		Size IContentView.CrossPlatformMeasure(double widthConstraint, double heightConstraint) =>
+			((ICrossPlatformLayout)this).CrossPlatformMeasure(widthConstraint, heightConstraint);
 
 		Size IContentView.CrossPlatformArrange(Rect bounds) =>
 			((ICrossPlatformLayout)this).CrossPlatformArrange(bounds);

src/Core/src/Handlers/ScrollView/ScrollViewHandler.Android.cs

@@ -25,14 +25,12 @@ protected override void ConnectHandler(MauiScrollView platformView)
 		{
 			base.ConnectHandler(platformView);
 			platformView.ScrollChange += ScrollChange;
-			platformView.CrossPlatformArrange = VirtualView.CrossPlatformArrange;
 		}
 
 		protected override void DisconnectHandler(MauiScrollView platformView)
 		{
 			base.DisconnectHandler(platformView);
 			platformView.ScrollChange -= ScrollChange;
-			platformView.CrossPlatformArrange = null;
 		}
 
 		public override Size GetDesiredSize(double widthConstraint, double heightConstraint)
@@ -234,7 +232,10 @@ static void InsertInsetView(IScrollViewHandler handler, IScrollView scrollView,
 
 		Size ICrossPlatformLayout.CrossPlatformMeasure(double widthConstraint, double heightConstraint)
 		{
-			var scrollView = VirtualView;
+			if (VirtualView is not { } scrollView)
+			{
+				return Size.Zero;
+			}
 
 			var padding = scrollView.Padding;
 
@@ -243,31 +244,25 @@ Size ICrossPlatformLayout.CrossPlatformMeasure(double widthConstraint, double he
 				return new Size(padding.HorizontalThickness, padding.VerticalThickness);
 			}
 
-			// Exclude the padding while measuring the internal content ...
-			var measurementWidth = widthConstraint - padding.HorizontalThickness;
-			var measurementHeight = heightConstraint - padding.VerticalThickness;
-
-			var result = (scrollView as ICrossPlatformLayout).CrossPlatformMeasure(measurementWidth, measurementHeight);
-
-			// ... and add the padding back in to the final result
-			var fullSize = new Size(result.Width + padding.HorizontalThickness, result.Height + padding.VerticalThickness);
+			var scrollOrientation = scrollView.Orientation;
+			var contentWidthConstraint = scrollOrientation is ScrollOrientation.Horizontal or ScrollOrientation.Both ? double.PositiveInfinity : widthConstraint;
+			var contentHeightConstraint = scrollOrientation is ScrollOrientation.Vertical or ScrollOrientation.Both ? double.PositiveInfinity : heightConstraint;
+			var contentSize = scrollView.MeasureContent(scrollView.Padding, contentWidthConstraint, contentHeightConstraint, !double.IsInfinity(contentWidthConstraint), !double.IsInfinity(contentHeightConstraint));
 
 			if (double.IsInfinity(widthConstraint))
 			{
-				widthConstraint = result.Width;
+				widthConstraint = contentSize.Width;
 			}
 
 			if (double.IsInfinity(heightConstraint))
 			{
-				heightConstraint = result.Height;
+				heightConstraint = contentSize.Height;
 			}
 
-			return fullSize.AdjustForFill(new Rect(0, 0, widthConstraint, heightConstraint), scrollView.PresentedContent);
+			return contentSize.AdjustForFill(new Rect(0, 0, widthConstraint, heightConstraint), scrollView.PresentedContent);
 		}
 
-		Size ICrossPlatformLayout.CrossPlatformArrange(Rect bounds)
-		{
-			return (VirtualView as ICrossPlatformLayout).CrossPlatformArrange(bounds);
-		}
+		Size ICrossPlatformLayout.CrossPlatformArrange(Rect bounds) =>
+			(VirtualView as ICrossPlatformLayout)?.CrossPlatformArrange(bounds) ?? Size.Zero;
 	}
 }

src/Core/src/Layouts/LayoutExtensions.cs

@@ -167,6 +167,37 @@ public static Size MeasureContent(this IContentView contentView, Thickness inset
 			return new Size(contentSize.Width + inset.HorizontalThickness, contentSize.Height + inset.VerticalThickness);
 		}
 
+		internal static Size MeasureContent(
+			this IContentView contentView,
+			Thickness inset,
+			double widthConstraint,
+			double heightConstraint,
+			bool constrainPresentedContentWidthToExplicitDimsOnContentView,
+			bool constrainPresentedContentHeightToExplicitDimsOnContentView)
+		{
+			var content = contentView.PresentedContent;
+
+			if (Dimension.IsExplicitSet(contentView.Width) && constrainPresentedContentWidthToExplicitDimsOnContentView)
+			{
+				widthConstraint = contentView.Width;
+			}
+
+			if (Dimension.IsExplicitSet(contentView.Height) && constrainPresentedContentHeightToExplicitDimsOnContentView)
+			{
+				heightConstraint = contentView.Height;
+			}
+
+			var contentSize = Size.Zero;
+
+			if (content != null)
+			{
+				contentSize = content.Measure(widthConstraint - inset.HorizontalThickness,
+					heightConstraint - inset.VerticalThickness);
+			}
+
+			return new Size(contentSize.Width + inset.HorizontalThickness, contentSize.Height + inset.VerticalThickness);
+		}
+
 		public static void ArrangeContent(this IContentView contentView, Rect bounds)
 		{
 			if (contentView.PresentedContent == null)

src/Core/src/Platform/Android/MauiScrollView.cs

@@ -97,7 +97,11 @@ public void SetOrientation(ScrollOrientation orientation)
 			{
 				if (_hScrollView == null)
 				{
-					_hScrollView = new MauiHorizontalScrollView(Context, this);
+					_hScrollView = new MauiHorizontalScrollView(Context, this)
+					{
+						FillViewport = true
+					};
+
 					_hScrollView.HorizontalFadingEdgeEnabled = HorizontalFadingEdgeEnabled;
 					_hScrollView.SetFadingEdgeLength(HorizontalFadingEdgeLength);
 					SetHorizontalScrollBarVisibility(_horizontalScrollVisibility);
@@ -229,15 +233,6 @@ protected override void OnLayout(bool changed, int left, int top, int right, int
 				hScrollViewHeight = _isBidirectional ? Math.Max(hScrollViewHeight, scrollViewContentHeight) : hScrollViewHeight;
 				_hScrollView.Layout(0, 0, hScrollViewWidth, hScrollViewHeight);
 			}
-
-			if (CrossPlatformArrange == null)
-			{
-				return;
-			}
-
-			var destination = Context!.ToCrossPlatformRectInReferenceFrame(left, top, right, bottom);
-
-			CrossPlatformArrange(destination);
 		}
 
 		public void ScrollTo(int x, int y, bool instant, Action finished)
@@ -321,8 +316,6 @@ void IOnScrollChangeListener.OnScrollChange(NestedScrollView? v, int scrollX, in
 		{
 			OnScrollChanged(scrollX, scrollY, oldScrollX, oldScrollY);
 		}
-
-		internal Func<Graphics.Rect, Graphics.Size>? CrossPlatformArrange { get; set; }
 	}
 
 	internal class MauiHorizontalScrollView : HorizontalScrollView, IScrollBarView