[Android] Fix for frame disappears when assigning GradientStops to Li…

…nearGradientBrush inside this Frame (#25851)

* Frame disappears issue has been fixed.

* added snapshot for Windows.

* Updated border color.

src/Controls/src/Core/Compatibility/Handlers/Android/FrameRenderer.cs

@@ -272,6 +272,8 @@ void UpdateBackground()
 					_backgroundDrawable = new GradientDrawable();
 					_backgroundDrawable.SetShape(ShapeType.Rectangle);
 					this.SetBackground(_backgroundDrawable);
+					UpdateBorderColor();
+					UpdateCornerRadius();
 				}
 
 				UpdateBackgroundColor();

src/Controls/tests/TestCases.HostApp/Issues/Issue23951.xaml

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage
+    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    x:Class="Maui.Controls.Sample.Issues.Issue23951">
+
+  <Grid RowDefinitions="Auto, Auto">
+        <Frame Grid.Row="0"
+               CornerRadius="10"
+               HeightRequest="30"
+               HorizontalOptions="FillAndExpand">
+            <Frame.Background>
+                <LinearGradientBrush x:Name="brush"
+                                     EndPoint="1,0"
+                                     GradientStops="{Binding GradientStops}">
+                </LinearGradientBrush>
+            </Frame.Background>
+        </Frame>
+        <Button Grid.Row="1"
+                Text="UpdateGradientStops"
+                AutomationId ="Button"
+                Command="{Binding ClickCommand}" />
+    </Grid>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue23951.xaml.cs

@@ -0,0 +1,55 @@
+using System;
+using System.ComponentModel;
+using System.Windows.Input;
+using Microsoft.Maui.Controls.Internals;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 23951, "[Android] Frame disappears when assigning GradientStops to LinearGradientBrush inside this Frame", PlatformAffected.Android)]
+	public partial class Issue23951: ContentPage
+	{
+		public Issue23951()
+		{
+			InitializeComponent();
+			BindingContext = new Issue23951ViewModel();
+		}
+
+	}
+
+	public partial class Issue23951ViewModel : INotifyPropertyChanged
+    {
+        public event PropertyChangedEventHandler PropertyChanged;
+        private GradientStopCollection _gradientStops = new GradientStopCollection();
+        public GradientStopCollection GradientStops
+        {
+            get => _gradientStops;
+            private set
+            {
+                _gradientStops = value;
+                OnPropertyChanged(nameof(GradientStops));
+            }
+        }
+        public void OnPropertyChanged(string propertyName)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+        public ICommand ClickCommand { get; private set; }
+        public Issue23951ViewModel()
+        {
+            UpdateGradientStops();
+            ClickCommand = new Command(Click);
+        }
+
+        private void Click(object obj)
+        {
+            UpdateGradientStops();
+        }
+
+        private void UpdateGradientStops()
+        {
+            GradientStops = new GradientStopCollection();
+            GradientStops.Add(new GradientStop(Color.Parse("Red"), 0f));
+            GradientStops.Add(new GradientStop(Color.Parse("Blue"), 1f));
+        }
+    }
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue23951.cs

@@ -0,0 +1,24 @@
+#if !MACCATALYST
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue23951 : _IssuesUITest
+	{
+		public Issue23951(TestDevice device) : base(device) { }
+
+		public override string Issue => "[Android] Frame disappears when assigning GradientStops to LinearGradientBrush inside this Frame";
+
+		[Test]
+		[Category(UITestCategories.Frame)]
+		public void FrameCornerRadiusShouldnotChange()
+		{
+			App.WaitForElement("Button");
+			App.Tap("Button");
+			VerifyScreenshot();
+		}
+	}
+}
+#endif