Merge pull request #3046 from unoplatform/dev/djo/animation-fix

fix(animation): [iOS] Fix InvalidCastException when app resumes while animation is active

src/Uno.UI.RuntimeTests/Tests/Windows_UI_Xaml_Media_Animation/Given_DoubleAnimation.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Media.Animation;
+
+namespace Uno.UI.RuntimeTests.Tests.Windows_UI_Xaml_Media_Animation
+{
+	[TestClass]
+	public class Given_DoubleAnimation
+	{
+		[TestMethod]
+		[RunsOnUIThread]
+		public void When_SeekAlignedToLastTick()
+		{
+			var target = new Border();
+			var doubleAnimation = new DoubleAnimation()
+			{
+				From = 50d,
+				To = 100d,
+				EnableDependentAnimation = true
+			};
+			Storyboard.SetTarget(doubleAnimation, target);
+			Storyboard.SetTargetProperty(doubleAnimation, "Height");
+			var sb = new Storyboard()
+			{
+				Children =
+				{
+					doubleAnimation
+				}
+			};
+
+			sb.Begin();
+			sb.SeekAlignedToLastTick(TimeSpan.FromMilliseconds(50));
+		}
+	}
+}

src/Uno.UI/UI/Xaml/Media/Animation/Timeline.animation.cs

@@ -177,7 +177,7 @@ public void Seek(TimeSpan offset)
 			public void SeekAlignedToLastTick(TimeSpan offset)
 			{
 				// Same as Seek
-				((ITimeline)this).Seek(offset);
+				Seek(offset);
 			}
 
 			public void SkipToFill()
@@ -296,7 +296,7 @@ private void Play()
 				// state. (The ideal would probably be to restart the animation when the app resumes.)
 				if (Application.Current?.IsSuspended ?? false)
 				{
-					((ITimeline)this).SkipToFill();
+					SkipToFill();
 				}
 #endif
 			}