[Android] Fix crash setting SelectedTabColor on TabbedPage (#12924) F…

…ixes #12904

* Fix crash setting SelectedTabColor on Android TabbedPage

* Update src/Controls/src/Core/Platform/Android/TabbedPageManager.cs

Co-authored-by: Manuel de la Pena <mandel@microsoft.com>

* Refactoring code

* Small refactoring and included comments

* Changes based on feedback

---------

Co-authored-by: Manuel de la Pena <mandel@microsoft.com>

src/Controls/src/Core/Platform/Android/TabbedPageManager.cs

@@ -549,41 +549,50 @@ internal void UpdateBarBackground()
 
 		protected virtual ColorStateList GetItemTextColorStates()
 		{
-			if (_originalTabTextColors == null)
-				_originalTabTextColors = (IsBottomTabPlacement) ? _bottomNavigationView.ItemTextColor : _tabLayout.TabTextColors;
+			if (_originalTabTextColors is null)
+				_originalTabTextColors = IsBottomTabPlacement ? _bottomNavigationView.ItemTextColor : _tabLayout.TabTextColors;
 
 			Color barItemColor = BarItemColor;
 			Color barTextColor = Element.BarTextColor;
 			Color barSelectedItemColor = BarSelectedItemColor;
 
-			if (barItemColor == null && barTextColor == null && barSelectedItemColor == null)
+			if (barItemColor is null && barTextColor is null && barSelectedItemColor is null)
 				return _originalTabTextColors;
 
-			if (_newTabTextColors != null)
+			if (_newTabTextColors is not null)
 				return _newTabTextColors;
 
 			int checkedColor;
-			int defaultColor;
 
-			if (barTextColor != null)
+			// The new default color to use may have a color if BarItemColor is not null or the original colors for text
+			// are not null either. If it does not happens, this variable will be null and the ColorStateList of the
+			// original colors is used.
+			int? defaultColor = null;
+
+			if (barTextColor is not null)
 			{
 				checkedColor = barTextColor.ToPlatform().ToArgb();
 				defaultColor = checkedColor;
 			}
 			else
 			{
-				defaultColor = barItemColor.ToPlatform().ToArgb();
+				if (barItemColor is not null)
+					defaultColor = barItemColor.ToPlatform().ToArgb();
 
-				if (barItemColor == null && _originalTabTextColors != null)
+				if (barItemColor is null && _originalTabTextColors is not null)
 					defaultColor = _originalTabTextColors.DefaultColor;
 
-				checkedColor = defaultColor;
+				if (!defaultColor.HasValue)
+					return _originalTabTextColors;
+				else
+					checkedColor = defaultColor.Value;
 
-				if (barSelectedItemColor != null)
+				if (barSelectedItemColor is not null)
 					checkedColor = barSelectedItemColor.ToPlatform().ToArgb();
 			}
 
-			_newTabTextColors = GetColorStateList(defaultColor, checkedColor);
+			_newTabTextColors = GetColorStateList(defaultColor.Value, checkedColor);
+
 			return _newTabTextColors;
 		}
 

src/Controls/tests/DeviceTests/Elements/TabbedPage/TabbedPageTests.Android.cs

@@ -0,0 +1,28 @@
+using System.Threading.Tasks;
+using AndroidX.ViewPager2.Widget;
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.DeviceTests.Stubs;
+using Microsoft.Maui.Graphics;
+using Xunit;
+
+namespace Microsoft.Maui.DeviceTests
+{
+	public partial class TabbedPageTests
+	{
+		[Fact(DisplayName = "Using SelectedTab Color doesnt crash")]
+		public async Task SelectedTabColorNoDoesntCrash()
+		{
+			SetupBuilder();
+
+			var tabbedPage = CreateBasicTabbedPage();
+			tabbedPage.SelectedTabColor = Colors.Red;
+
+			await CreateHandlerAndAddToWindow<WindowHandlerStub>(new Window(tabbedPage), (handler) =>
+			{
+				var platformView = tabbedPage.Handler.PlatformView as ViewPager2;
+				Assert.NotNull(platformView);
+				return Task.CompletedTask;
+			});
+		}
+	}
+}