[Android] Fix issue updating background brush

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue13017.xaml

@@ -0,0 +1,59 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<controls:TestContentPage
+    xmlns:controls="clr-namespace:Xamarin.Forms.Controls"
+    xmlns="http://xamarin.com/schemas/2014/forms"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    xmlns:d="http://xamarin.com/schemas/2014/forms/design"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d"
+    x:Class="Xamarin.Forms.Controls.Issues.Issue13017">
+    <StackLayout>
+        <Label
+            Padding="12"
+            BackgroundColor="Black"
+            TextColor="White"
+            Text="Switch between both Backgrounds several times. If the change works as expected, the test has passed."/>
+        <StackLayout>
+            <Frame
+                WidthRequest="50"
+			    HeightRequest="100"
+			    Padding="0">
+                <Frame.Style>
+                    <Style TargetType="Frame">
+                        <Style.Triggers>
+                            <DataTrigger TargetType="Frame"
+									 Binding="{Binding BackgroundNumber}"
+									 Value="1">
+                                <Setter Property="Background">
+                                    <Setter.Value>
+                                        <LinearGradientBrush
+                                            StartPoint="0,0"
+                                            EndPoint="1,0.5">
+                                            <GradientStop Color="#00FFD1" Offset="0"/>
+                                            <GradientStop Color="#5263FF" Offset="1"/>
+                                        </LinearGradientBrush>
+                                    </Setter.Value>
+                                </Setter>
+                            </DataTrigger>
+                            <DataTrigger TargetType="Frame"
+									 Binding="{Binding BackgroundNumber}"
+									 Value="2">
+                                <Setter Property="Background">
+                                    <Setter.Value>
+                                        <SolidColorBrush Color="Red"/>
+                                    </Setter.Value>
+                                </Setter>
+                            </DataTrigger>
+                        </Style.Triggers>
+                    </Style>
+                </Frame.Style>
+            </Frame>
+            <Button
+                Text="Use Gradient"
+				Command="{Binding SelectGradient}"/>
+            <Button
+                Text="Use SolidColorBrush"
+				Command="{Binding SelectSolidBrushGradient}"/>
+        </StackLayout>
+    </StackLayout>
+</controls:TestContentPage>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue13017.xaml.cs

@@ -0,0 +1,82 @@
+using System;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using System.Windows.Input;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.Xaml;
+
+#if UITEST
+using Xamarin.UITest;
+using Xamarin.UITest.Queries;
+using NUnit.Framework;
+using Xamarin.Forms.Core.UITests;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[NUnit.Framework.Category(UITestCategories.Brush)]
+#endif
+#if APP
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 13017, "[Bug] Background doesn't change from LinearGradientBrush to SolidColorBrush by DataTrigger on Android",
+		PlatformAffected.Android)]
+	public partial class Issue13017 : TestContentPage
+	{
+		public Issue13017()
+		{
+#if APP
+			Title = "Issue 13017";
+			InitializeComponent();
+			BindingContext = new Issue13017ViewModel();
+#endif
+		}
+
+		protected override void Init()
+		{
+
+		}
+	}
+
+	[Preserve(AllMembers = true)]
+	public class Issue13017ViewModel : INotifyPropertyChanged
+	{
+		int _backgroundNumber = 1;
+
+		public Issue13017ViewModel()
+		{
+			SelectGradient = new Command(() =>
+			{
+				BackgroundNumber = 1;
+			});
+
+			SelectSolidBrushGradient = new Command(() =>
+			{
+				BackgroundNumber = 2;
+			});
+		}
+
+		public event PropertyChangedEventHandler PropertyChanged;
+
+		public ICommand SelectGradient { get; private set; }
+		public ICommand SelectSolidBrushGradient { get; private set; }
+
+		public int BackgroundNumber
+		{
+			get => _backgroundNumber;
+			set
+			{
+				_backgroundNumber = value;
+				OnPropertyChanged(nameof(BackgroundNumber));
+			}
+		}
+
+		protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
+		{
+			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -1762,6 +1762,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue8988.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12084.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12512.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue13017.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8981.xaml.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue3311.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue12473.xaml.cs">
@@ -2221,6 +2222,9 @@
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue12084.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue13017.xaml">
+      <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
+    </EmbeddedResource>
     <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue8981.xaml">
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>

Xamarin.Forms.Platform.Android/FastRenderers/FrameRenderer.cs

@@ -299,8 +299,9 @@ void UpdateBackground()
 				this.SetBackground(null);
 
 				_backgroundDrawable = new GradientDrawable();
-
+	      _backgroundDrawable.SetShape(ShapeType.Rectangle);
 				this.SetBackground(_backgroundDrawable);
+
 				UpdateBorderColor();
 				UpdateCornerRadius();
 			}