[Android] Set Page background color (#5066) * Fixes #5057 * closes #4916 * Fixes #5073

* [Android] Fix setting Page background color

* Update Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5057.xaml.cs

Co-Authored-By: andreinitescu <nitescua@yahoo.com>

* Update Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5057.xaml.cs

Co-Authored-By: andreinitescu <nitescua@yahoo.com>

* Refactoring and added test info

* Update Xamarin.Forms.Platform.Android/Renderers/PageRenderer.cs

Co-Authored-By: andreinitescu <nitescua@yahoo.com>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5057.xaml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Xamarin.Forms.Controls.Issues.Issue5057">
+	<StackLayout Padding="10">
+		<Label Text="When both Page.BackgroundImage and Page.BackgroundColor are set, the BackgroundImage takes precedence."/>
+		<Label Text="If Page.BackgroundImage is set, setting BackgroundColor won't be have any visual effect"/>
+		<Label Text="Clearing the BackgroundImage by setting it to null, makes Page background displayed with BackgroundColor"/>
+		<Button Text="Set background color to Red" 
+                Clicked="BtnSetBkgndColorRed_Clicked"
+                BackgroundColor="White"/>
+		<Button Text="Set background image" 
+                Clicked="BtnSetBkgndImg_Clicked" 
+                BackgroundColor="White"/>
+		<Button Text="Set background color to default" 
+                Clicked="BtnSetBkgndColorDefault_Clicked" 
+                BackgroundColor="White"/>
+		<Button Text="Set background image to null" 
+                Clicked="BtnSetBkgndImgNull_Clicked" 
+                BackgroundColor="White"/>
+	</StackLayout>
+</ContentPage>

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue5057.xaml.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Collections.Generic;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.Xaml;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if APP
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 5057, "Android: ContentPage BackgroundColor ignored in Forms ",
+		PlatformAffected.Android)]
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	public partial class Issue5057 : ContentPage
+	{
+		public Issue5057()
+		{
+			InitializeComponent();
+		}
+
+		void BtnSetBkgndColorRed_Clicked(object sender, System.EventArgs e)
+		{
+			BackgroundColor = Color.Red;
+		}
+
+		void BtnSetBkgndImg_Clicked(object sender, System.EventArgs e)
+		{
+			BackgroundImage = "test.jpg";
+		}
+
+		void BtnSetBkgndColorDefault_Clicked(object sender, System.EventArgs e)
+		{
+			BackgroundColor = (Color)BackgroundColorProperty.DefaultValue;
+		}
+
+		void BtnSetBkgndImgNull_Clicked(object sender, System.EventArgs e)
+		{
+			BackgroundImage = null;
+		}
+	}
+#endif
+}

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

@@ -428,6 +428,10 @@
       <SubType>Code</SubType>
     </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Issue4600.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue5057.xaml.cs">
+      <DependentUpon>Issue5057.xaml</DependentUpon>
+      <SubType>Code</SubType>
+    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)LegacyComponents\NonAppCompatSwitch.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)MapsModalCrash.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ModalActivityIndicatorTest.cs" />
@@ -1091,4 +1095,10 @@
       <Generator>MSBuild:UpdateDesignTimeXaml</Generator>
     </EmbeddedResource>
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue5057.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </EmbeddedResource>
+  </ItemGroup>
 </Project>

Xamarin.Forms.Platform.Android/Renderers/PageRenderer.cs

@@ -62,8 +62,7 @@ namespace Xamarin.Forms.Platform.Android
 				Id = Platform.GenerateViewId();
 			}
 
-			UpdateBackgroundColor(view);
-			UpdateBackgroundImage(view);
+			UpdateBackground(false);
 
 			Clickable = true;
 		}
@@ -72,9 +71,9 @@ namespace Xamarin.Forms.Platform.Android
 		{
 			base.OnElementPropertyChanged(sender, e);
 			if (e.PropertyName == Page.BackgroundImageProperty.PropertyName)
-				UpdateBackgroundImage(Element);
+				UpdateBackground(true);
 			else if (e.PropertyName == VisualElement.BackgroundColorProperty.PropertyName)
-				UpdateBackgroundColor(Element);
+				UpdateBackground(false);
 			else if (e.PropertyName == VisualElement.HeightProperty.PropertyName)
 				UpdateHeight();
 		}
@@ -105,22 +104,25 @@ namespace Xamarin.Forms.Platform.Android
 			_previousHeight = newHeight;
 		}
 
-		void UpdateBackgroundColor(Page view)
+		void UpdateBackground(bool setBkndColorEvenWhenItsDefault)
 		{
-			if (view.Parent is BaseShellItem)
-			{
-				var background = view.BackgroundColor;
-				var color = Context.Resources.GetColor(global::Android.Resource.Color.BackgroundLight, Context.Theme);
-				SetBackgroundColor(background.IsDefault ? color : background.ToAndroid());
-			}
-			else if (view.BackgroundColor != Color.Default)
-				SetBackgroundColor(view.BackgroundColor.ToAndroid());
-		}
+			Page page = Element;
 
-		void UpdateBackgroundImage(Page view)
-		{
-			if (!string.IsNullOrEmpty(view.BackgroundImage))
-				this.SetBackground(Context.GetDrawable(view.BackgroundImage));
+			string bkgndImage = page.BackgroundImage;
+			if (!string.IsNullOrEmpty(bkgndImage))
+				this.SetBackground(Context.GetDrawable(bkgndImage));
+			else
+			{
+				Color bkgndColor = page.BackgroundColor;
+				bool isDefaultBkgndColor = bkgndColor.IsDefault;
+				if (page.Parent is BaseShellItem && isDefaultBkgndColor)
+				{
+					var color = Context.Resources.GetColor(global::Android.Resource.Color.BackgroundLight, Context.Theme);
+					SetBackgroundColor(color);
+				}
+				else if (!isDefaultBkgndColor || setBkndColorEvenWhenItsDefault)
+					SetBackgroundColor(bkgndColor.ToAndroid());
+			}
 		}
 	}
 }