[iOS] Block the scroll if is swiping a SwipeView (#11949) fixes #11651 fixes #11932

* Block the scroll if is swiping a SwipeView on iOS

* Updated MinimumOpenSwipeThresholdPercentage

Author: jsuarezruiz

Xamarin.Forms.Platform.iOS/Extensions/UIViewExtensions.cs

@@ -35,6 +35,24 @@ public static UIImage ConvertToImage(this UIView view)
 		}
 #endif
 
+		internal static T GetParentOfType<T>(this UIView view)
+			where T : class
+		{
+			if (view is T t)
+				return t;
+
+			while (view != null)
+			{
+				T parent = view.Superview as T;
+				if (parent != null)
+					return parent;
+
+				view = view.Superview;
+			}
+
+			return default(T);
+		}
+
 		public static IEnumerable<UIView> Descendants(this UIView self)
 		{
 			if (self.Subviews == null)

Xamarin.Forms.Platform.iOS/Renderers/SwipeViewRenderer.cs

@@ -13,6 +13,7 @@ namespace Xamarin.Forms.Platform.iOS
 {
 	public class SwipeViewRenderer : ViewRenderer<SwipeView, UIView>
 	{
+		const float MinimumOpenSwipeThresholdPercentage = 0.15f; // 15%
 		const float OpenSwipeThresholdPercentage = 0.6f; // 60%
 		const double SwipeThreshold = 250;
 		const double SwipeItemWidth = 100;
@@ -38,6 +39,7 @@ public class SwipeViewRenderer : ViewRenderer<SwipeView, UIView>
 		double _previousScrollY;
 		int _previousFirstVisibleIndex;
 		bool _isSwipeEnabled;
+		bool _isScrollEnabled;
 		bool _isResettingSwipe;
 		bool _isOpen;
 		bool _isDisposed;
@@ -48,6 +50,7 @@ public SwipeViewRenderer()
 			SwipeView.VerifySwipeViewFlagEnabled(nameof(SwipeViewRenderer));
 
 			_swipeItems = new Dictionary<ISwipeItem, object>();
+			_isScrollEnabled = true;
 
 			_tapGestureRecognizer = new UITapGestureRecognizer(HandleTap)
 			{
@@ -763,7 +766,10 @@ void ProcessTouchMove(CGPoint point)
 			UpdateIsOpen(_swipeOffset != 0);
 
 			if (Math.Abs(_swipeOffset) > double.Epsilon)
+			{
+				IsParentScrollEnabled(false);
 				Swipe();
+			}
 
 			RaiseSwipeChanging();
 		}
@@ -779,6 +785,7 @@ void ProcessTouchUp(CGPoint point)
 				return;
 
 			_isSwiping = false;
+			IsParentScrollEnabled(true);
 
 			RaiseSwipeEnded();
 
@@ -788,6 +795,24 @@ void ProcessTouchUp(CGPoint point)
 			ValidateSwipeThreshold();
 		}
 
+		void IsParentScrollEnabled(bool scrollEnabled)
+		{
+			var swipeThresholdPercent = MinimumOpenSwipeThresholdPercentage * GetSwipeThreshold();
+
+			if (Math.Abs(_swipeOffset) < swipeThresholdPercent)
+				return;
+
+			if (scrollEnabled == _isScrollEnabled)
+				return;
+
+			_isScrollEnabled = scrollEnabled;
+
+			var parent = this.GetParentOfType<UIScrollView>();
+
+			if (parent != null)
+				parent.ScrollEnabled = _isScrollEnabled;
+		}
+
 		bool CanProcessTouchSwipeItems(CGPoint point)
 		{
 			// We only invoke the SwipeItem command if we tap on the SwipeItems area