Reseting thumb image

src/Controls/tests/TestCases.HostApp/Issues/Issue25939.xaml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ContentPage xmlns:controls="clr-namespace:Maui.Controls.Sample.Issues"
+             xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue25939">
+        <StackLayout>
+                <Slider
+                        x:Name="SliderControl"
+                        WidthRequest="300"
+                        HeightRequest="50"
+                        Minimum="0"
+                        Maximum="100"
+                        Value="50"/>
+
+                <Button
+                        AutomationId="ChangeThumbImageSourceButton"
+                        Text="Change thumb image source"
+                        Clicked="OnThumbImageSourceButtonClicked"/>
+
+                <Slider
+                        x:Name="SliderControl2"
+                        WidthRequest="300"
+                        HeightRequest="50"
+                        Minimum="0"
+                        Maximum="100"
+                        Value="50"/>
+
+                <Button
+                        AutomationId="ResetThumbImageSourceButton"
+                        Text="Reset thumb"
+                        Clicked="OnResetButtonClicked"/>
+
+        </StackLayout>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue25939.xaml.cs

@@ -0,0 +1,21 @@
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 25939, "Unable to Remove Thumb Image in Slider Control ", PlatformAffected.Android | PlatformAffected.iOS)]
+	public partial class Issue25939 : ContentPage
+	{
+		public Issue25939()
+		{
+			InitializeComponent();
+		}
+
+		private void OnThumbImageSourceButtonClicked(object sender, EventArgs e)
+		{
+			SliderControl.ThumbImageSource = "coffee.png";
+			SliderControl2.ThumbImageSource = "coffee.png";
+		}
+		private void OnResetButtonClicked(object sender, EventArgs e)
+		{
+			SliderControl2.ThumbImageSource = null;
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue25939.cs

@@ -0,0 +1,25 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue25939 : _IssuesUITest
+	{
+		public Issue25939(TestDevice testDevice) : base(testDevice)
+		{
+		}
+
+		public override string Issue => "Unable to Remove Thumb Image in Slider Control ";
+
+		[Test]
+		[Category(UITestCategories.Slider)]
+		public void SliderShouldChangeThumbImageAndResetIt()
+		{
+			App.WaitForElement("ChangeThumbImageSourceButton");
+			App.Click("ChangeThumbImageSourceButton");
+			App.Click("ResetThumbImageSourceButton");
+			VerifyScreenshot();
+		}
+	}
+}

src/Core/src/Platform/Android/SliderExtensions.cs

@@ -1,7 +1,7 @@
 using System.Threading.Tasks;
 using Android.Content.Res;
 using Android.Graphics;
-using Android.Graphics.Drawables;
+using Android.Util;
 using Android.Widget;
 
 namespace Microsoft.Maui.Platform
@@ -63,6 +63,21 @@ public static async Task UpdateThumbImageSourceAsync(this SeekBar seekBar, ISlid
 				if (seekBar.IsAlive() && thumbDrawable != null)
 					seekBar.SetThumb(thumbDrawable);
 			}
+			else
+			{
+				seekBar.SetThumb(context.GetDrawable(Resource.Drawable.abc_seekbar_thumb_material));
+				if (slider.ThumbColor is null && context.Theme is not null)
+				{
+					using var value = new TypedValue();
+					context.Theme.ResolveAttribute(Android.Resource.Attribute.ColorAccent, value, true);
+					var color = new Color(value.Data);
+					seekBar.Thumb?.SetColorFilter(color, FilterMode.SrcIn);
+				}
+				else
+				{
+					seekBar.UpdateThumbColor(slider);
+				}
+			}
 		}
 	}
 }

src/Core/src/Platform/iOS/SliderExtensions.cs

@@ -54,6 +54,11 @@ public static async Task UpdateThumbImageSourceAsync(this UISlider uiSlider, ISl
 
 				uiSlider.SetThumbImage(thumbImage, UIControlState.Normal);
 			}
+			else
+			{
+				uiSlider.SetThumbImage(null, UIControlState.Normal);
+				uiSlider.UpdateThumbColor(slider);
+			}
 		}
 	}
 }