[Android] CarouselView: Fix touch interception to delegate vertical swipes to nested views

src/Controls/src/Core/Handlers/Items/Android/MauiCarouselRecyclerView.cs

@@ -19,7 +19,11 @@ public class MauiCarouselRecyclerView : MauiRecyclerView<CarouselView, ItemsView
 		bool _isVisible;
 		bool _disposed;
 		bool _isInternalPositionUpdate;
-
+		readonly float _touchSlop;
+		float _initialTouchX;
+		float _initialTouchY;
+		bool _directionLocked;
+		bool _delegatingToChild;
 		List<View> _oldViews;
 		CarouselViewOnGlobalLayoutListener _carouselViewLayoutListener;
 
@@ -29,20 +33,94 @@ public MauiCarouselRecyclerView(Context context, Func<IItemsLayout> getItemsLayo
 		{
 			_oldViews = new List<View>();
 			_carouselViewLoopManager = new CarouselViewLoopManager();
+			_touchSlop = ViewConfiguration.Get(context).ScaledTouchSlop;
 		}
 
+		// Gets or sets a value indicating whether swipe gestures are enabled for the carousel.
 		public bool IsSwipeEnabled { get; set; }
 
 		public override bool OnInterceptTouchEvent(MotionEvent ev)
 		{
+			// If ItemsView is explicitly disabled, defer to the base implementation so it can
+			// intercept all touch events and block interaction. Returning false here (for either
+			// the swipe-disabled or off-axis delegation paths) would bypass that guard and allow
+			// a disabled CarouselView to delegate gestures to a nested child.
+			if (ItemsView?.IsEnabled == false && !ItemsView.IsExplicitlyEnabled)
+			{
+				return base.OnInterceptTouchEvent(ev);
+			}
+
 			if (!IsSwipeEnabled)
 			{
 				return false;
 			}
 
+			switch (ev.Action)
+			{
+				case MotionEventActions.Down:
+					_initialTouchX = ev.GetX();
+					_initialTouchY = ev.GetY();
+					_directionLocked = false;
+					_delegatingToChild = false;
+					break;
+
+				case MotionEventActions.Move:
+					// Once a gesture has been delegated to a nested child, keep delegating for the
+					// rest of the gesture. This prevents a later ambiguous move - or the child
+					// reaching its scroll boundary - from letting the carousel hijack the swipe and
+					// transition to the next item.
+					if (_delegatingToChild)
+					{
+						return false;
+					}
+
+					if (!_directionLocked)
+					{
+						float deltaX = ev.GetX() - _initialTouchX;
+						float deltaY = ev.GetY() - _initialTouchY;
+
+						// Lock the gesture direction the first time movement exceeds touch slop.
+						if (Math.Abs(deltaX) > _touchSlop || Math.Abs(deltaY) > _touchSlop)
+						{
+							_directionLocked = true;
+
+							if (IsOffAxisGesture(deltaX, deltaY))
+							{
+								// Perpendicular gesture (e.g. a vertical swipe on a horizontal carousel):
+								// it belongs to nested scrollable content, never the carousel.
+								_delegatingToChild = true;
+								return false;
+							}
+						}
+					}
+					break;
+
+				case MotionEventActions.Cancel:
+				case MotionEventActions.Up:
+					// Reset gesture state at the end of the gesture
+					// to prevent old values from being used if we don't get a Down event
+					_initialTouchX = 0;
+					_initialTouchY = 0;
+					_directionLocked = false;
+					_delegatingToChild = false;
+					break;
+			}
+
 			return base.OnInterceptTouchEvent(ev);
 		}
 
+		// Determines whether the gesture's dominant axis is the opposite of the carousel's scroll
+		// orientation (e.g. a vertical swipe on a horizontal carousel). Off-axis gestures belong to
+		// nested scrollable content, so the carousel must not intercept them.
+		bool IsOffAxisGesture(float deltaX, float deltaY)
+		{
+			float absDeltaX = Math.Abs(deltaX);
+			float absDeltaY = Math.Abs(deltaY);
+			bool isVerticalGesture = absDeltaY > absDeltaX;
+
+			return IsHorizontal ? isVerticalGesture : !isVerticalGesture;
+		}
+
 		protected virtual bool IsHorizontal => (Carousel?.ItemsLayout)?.Orientation == ItemsLayoutOrientation.Horizontal;
 
 		protected override int DetermineTargetPosition(ScrollToRequestEventArgs args)

src/Controls/tests/DeviceTests/Elements/CarouselView/CarouselViewTests.Android.cs

@@ -1,5 +1,6 @@
 using System.Collections.ObjectModel;
 using System.Threading.Tasks;
+using Android.Views;
 using Android.Widget;
 using AndroidX.RecyclerView.Widget;
 using Microsoft.Maui.Controls;
@@ -55,6 +56,60 @@ await CreateHandlerAndAddToWindow<CarouselViewHandler>(carouselView, async (hand
 			});
 		}
 
+		[Fact(DisplayName = "Vertical Drag On Horizontal CarouselView Is Not Intercepted")]
+		public async Task VerticalDragOnHorizontalCarouselIsNotIntercepted()
+		{
+			SetupBuilder();
+
+			var data = new ObservableCollection<string> { "Item 1", "Item 2", "Item 3" };
+
+			var template = new DataTemplate(() => new Grid { new Label() });
+
+			var carouselView = new CarouselView
+			{
+				ItemTemplate = template,
+				ItemsSource = data,
+				IsSwipeEnabled = true,
+			};
+
+			await CreateHandlerAndAddToWindow<CarouselViewHandler>(carouselView, async (handler) =>
+			{
+				var recyclerView = handler.PlatformView;
+				await recyclerView.WaitForLayoutOrNonZeroSize();
+
+				// A vertical-dominant drag with a horizontal component large enough that the base
+				// RecyclerView would otherwise treat it as a horizontal page swipe. The fix must
+				// detect the off-axis gesture and delegate it to nested scrollable content, so
+				// OnInterceptTouchEvent returns false. Without the fix, the carousel intercepts it.
+				bool intercepted = SimulateDragIntercept(recyclerView, deltaX: 80, deltaY: 400);
+
+				Assert.False(intercepted);
+			});
+		}
+
+		// Dispatches a synthetic down/move/up gesture to the RecyclerView's touch-interception
+		// pipeline and reports whether the move was intercepted by the carousel.
+		static bool SimulateDragIntercept(RecyclerView recyclerView, float deltaX, float deltaY)
+		{
+			const float startX = 200f;
+			const float startY = 200f;
+			long downTime = global::Android.OS.SystemClock.UptimeMillis();
+
+			var down = MotionEvent.Obtain(downTime, downTime, MotionEventActions.Down, startX, startY, 0);
+			recyclerView.OnInterceptTouchEvent(down);
+			down.Recycle();
+
+			var move = MotionEvent.Obtain(downTime, downTime + 16, MotionEventActions.Move, startX + deltaX, startY + deltaY, 0);
+			bool intercepted = recyclerView.OnInterceptTouchEvent(move);
+			move.Recycle();
+
+			var up = MotionEvent.Obtain(downTime, downTime + 32, MotionEventActions.Up, startX + deltaX, startY + deltaY, 0);
+			recyclerView.OnInterceptTouchEvent(up);
+			up.Recycle();
+
+			return intercepted;
+		}
+
 		RecyclerView GetPlatformCarouselView(CarouselViewHandler carouselViewHandler) =>
 			carouselViewHandler.PlatformView;