Runtime updating of AppTheme values

Xamarin.Forms.Controls/GalleryPages/AppThemeGalleries/AppThemeCodeGallery.cs

@@ -1,42 +1,54 @@
-namespace Xamarin.Forms.Controls.GalleryPages.AppThemeGalleries
+using System;
+
+namespace Xamarin.Forms.Controls.GalleryPages.AppThemeGalleries
 {
 	public class AppThemeCodeGallery : ContentPage
 	{
-		AppThemeColor color = new AppThemeColor { Light = Color.Green, Dark = Color.Red };
-		public Color TheColor
-		{
-			get => color.Value;
-		}
+		Label _currentThemeLabel;
 
 		public AppThemeCodeGallery()
 		{
-			var currentThemeLabel = new Label
+			_currentThemeLabel = new Label
 			{
 				Text = Application.Current.RequestedTheme.ToString()
 			};
 
-			Application.Current.RequestedThemeChanged += (s, a) =>
+			Application.Current.RequestedThemeChanged += Current_RequestedThemeChanged;
+
+			var onThemeLabel = new Label
 			{
-				currentThemeLabel.Text = Application.Current.RequestedTheme.ToString();
-				OnPropertyChanged(nameof(TheColor));
+				Text = "TextColor through SetBinding"
 			};
 
-			var onThemeLabel = new Label
+			var onThemeLabel1 = new Label
+			{
+				Text = "TextColor through SetAppTheme"
+			};
+
+			var onThemeLabel2 = new Label
 			{
-				Text = "This text is green or red depending on Light (or default) or Dark"
+				Text = "TextColor through SetAppThemeColor"
 			};
 
-			onThemeLabel.SetBinding(Label.TextColorProperty, new Binding(nameof(TheColor)));
-			BindingContext = this;
+			onThemeLabel.SetBinding(Label.TextColorProperty, new AppThemeColor() { Light = Color.Green, Dark = Color.Red });
+
+			onThemeLabel1.SetOnAppTheme(Label.TextColorProperty, Color.Green, Color.Red);
+
+			onThemeLabel2.SetAppThemeColor(Label.TextColorProperty, Color.Green, Color.Red);
 
 			var stackLayout = new StackLayout
 			{
 				HorizontalOptions = LayoutOptions.Center,
 				VerticalOptions = LayoutOptions.Center,
-				Children = { currentThemeLabel, onThemeLabel }
+				Children = { _currentThemeLabel, onThemeLabel , onThemeLabel1,onThemeLabel2 }
 			};
 
 			Content = stackLayout;
 		}
+
+		private void Current_RequestedThemeChanged(object sender, AppThemeChangedEventArgs e)
+		{
+			_currentThemeLabel.Text = Application.Current.RequestedTheme.ToString();
+		}
 	}
 }

Xamarin.Forms.Controls/GalleryPages/AppThemeGalleries/AppThemeXamlGallery.xaml

@@ -1,6 +1,9 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:gallerypages="clr-namespace:Xamarin.Forms.Controls.GalleryPages.AppThemeGalleries" x:Class="Xamarin.Forms.Controls.GalleryPages.AppThemeGalleries.AppThemeXamlGallery" BackgroundColor="{OnAppTheme Light=Lightgray, Dark=Darkgray}">
+<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:gallerypages="clr-namespace:Xamarin.Forms.Controls.GalleryPages.AppThemeGalleries" x:Class="Xamarin.Forms.Controls.GalleryPages.AppThemeGalleries.AppThemeXamlGallery" BackgroundColor="{OnAppTheme Light=Lightgray, Dark=Black}">
     <ContentPage.Resources>
+        <ResourceDictionary>
+            <gallerypages:FooConverter x:Key="fooConv"/>
+        </ResourceDictionary>
         <AppThemeColor x:Key="MyColor" Light="HotPink" Dark="Yellow" />
         <Style x:Key="OSThemeStyle" TargetType="Label">
             <Setter Property="TextColor" Value="{OnAppTheme Black, Light=Green, Dark=Red}" />
@@ -26,19 +29,21 @@
     </ContentPage.Resources>
     <ScrollView>
         <StackLayout HorizontalOptions="Center" VerticalOptions="Center">
-            <Label TextColor="{OnAppTheme Light=Green, Dark=Red}">This text is green or red depending on Light (or default) or Dark</Label>
-            <Label Text="Testing 1, 2, 3">
+            <Label TextColor="{OnAppTheme Light=Green, Dark=Red}">OnAppThemeExtension</Label>
+            <Label Text="OnAppTheme XAML tag">
                 <Label.TextColor>
                     <OnAppTheme x:TypeArguments="Color" Light="Green" Dark="Red" />
                 </Label.TextColor>
             </Label>
-            <Label Style="{DynamicResource Key=OSThemeStyle}">This text is green or red depending on Light (or default) or Dark (through style)</Label>
-            <Label TextColor="{DynamicResource MyColor}">This text is HotPink or Yellow depending on Light (or default) or Dark (through DynamicResource)</Label>
-            <Label TextColor="{StaticResource MyColor}">This text is HotPink or Yellow depending on Light (or default) or Dark (through StaticResource)</Label>
+            <Label Style="{DynamicResource Key=OSThemeStyle}">DynamicResource Style</Label>
+            <Label TextColor="{DynamicResource MyColor}">DynamicResource Color</Label>
+            <Label TextColor="{StaticResource MyColor}">StaticResource</Label>
             <!--<Label x:Name="cssStyledLabel">This text is Purple or Orange depending on Light (or default) or Dark (through CSS)</Label>-->
-            <Label>The image below is a Xamarin logo or fruits depending on Light (or default) or Dark</Label>
+            <Label>Image with OnAppThemeExtension</Label>
             <Image Source="{OnAppTheme Light=xamarinlogo.png, Dark=Fruits.jpg}" />
-            <gallerypages:CustomControl TextColor="Brown" Text="This custom control should have brown text" />
+            <!--<gallerypages:CustomControl TextColor="Brown" Text="This custom control should have brown text" />-->
+            <Label TextColor="{OnAppTheme Light=1, Dark=2, Converter={StaticResource fooConv}}">With ValueConverter</Label>
+
         </StackLayout>
     </ScrollView>
 </ContentPage>

Xamarin.Forms.Controls/GalleryPages/AppThemeGalleries/AppThemeXamlGallery.xaml.cs

@@ -1,4 +1,7 @@
-using Xamarin.Forms.Xaml;
+using System;
+using System.Globalization;
+using Xamarin.Forms.Internals;
+using Xamarin.Forms.Xaml;
 
 namespace Xamarin.Forms.Controls.GalleryPages.AppThemeGalleries
 {
@@ -11,47 +14,62 @@ public AppThemeXamlGallery()
         }
 	}
 
-	public class CustomControl : ContentView
-    {
-        public static readonly BindableProperty TextColorProperty = BindableProperty.Create(nameof(TextColor), typeof(Color), typeof(CustomControl), (Color)new AppThemeColor() { Light = Color.Red, Dark = Color.Green });
-        public static readonly BindableProperty TextProperty = BindableProperty.Create(nameof(Text), typeof(string), typeof(CustomControl));
-        public static readonly BindableProperty BoxColorProperty = BindableProperty.Create(nameof(BoxColor), typeof(Color), typeof(CustomControl), Color.Yellow);
-
-        private StackLayout layout = new StackLayout();
-        public CustomControl()
-        {
-            var label = new Label();
-            label.SetBinding(Label.TextProperty, new Binding(nameof(Text), source: this));
-            label.SetBinding(Label.TextColorProperty, new Binding(nameof(TextColor), source: this, mode: BindingMode.TwoWay));
-            label.SetDynamicResource(Label.TextColorProperty, "MyColor");
-            this.layout.Children.Add(label);
-
-            var box = new BoxView();
-            box.SetBinding(BoxView.ColorProperty, new Binding(nameof(BoxColor), source: this, mode: BindingMode.TwoWay));
-            box.WidthRequest = 24;
-            box.HeightRequest = 24;
-            this.layout.Children.Add(box);
-
-            this.layout.Orientation = StackOrientation.Horizontal;
-            this.Content = this.layout;
-        }
+	[Preserve(AllMembers = true)]
+	class FooConverter : IValueConverter
+	{
+		public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+		{
+			var val = value as string;
+			return val == "1" ? Color.Green : Color.Red;
+		}
 
-        public Color TextColor
-        {
-            get { return (Color)this.GetValue(TextColorProperty); }
-            set { this.SetValue(TextColorProperty, value); }
-        }
+		public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+		{
+			throw new NotSupportedException("Only one way bindings are supported with this converter");
+		}
+	}
 
-        public string Text
-        {
-            get { return (string)this.GetValue(TextProperty); }
-            set { this.SetValue(TextProperty, value); }
-        }
+	//public class CustomControl : ContentView
+	//   {
+	//       public static readonly BindableProperty TextColorProperty = BindableProperty.Create(nameof(TextColor), typeof(Color), typeof(CustomControl), (Color)new AppThemeColor() { Light = Color.Red, Dark = Color.Green });
+	//       public static readonly BindableProperty TextProperty = BindableProperty.Create(nameof(Text), typeof(string), typeof(CustomControl));
+	//       public static readonly BindableProperty BoxColorProperty = BindableProperty.Create(nameof(BoxColor), typeof(Color), typeof(CustomControl), Color.Yellow);
 
-        public Color BoxColor
-        {
-            get { return (Color)this.GetValue(BoxColorProperty); }
-            set { this.SetValue(BoxColorProperty, value); }
-        }
-    } 
+	//       private StackLayout layout = new StackLayout();
+	//       public CustomControl()
+	//       {
+	//           var label = new Label();
+	//           label.SetBinding(Label.TextProperty, new Binding(nameof(Text), source: this));
+	//           label.SetBinding(Label.TextColorProperty, new Binding(nameof(TextColor), source: this, mode: BindingMode.TwoWay));
+	//           label.SetDynamicResource(Label.TextColorProperty, "MyColor");
+	//           this.layout.Children.Add(label);
+
+	//           var box = new BoxView();
+	//           box.SetBinding(BoxView.ColorProperty, new Binding(nameof(BoxColor), source: this, mode: BindingMode.TwoWay));
+	//           box.WidthRequest = 24;
+	//           box.HeightRequest = 24;
+	//           this.layout.Children.Add(box);
+
+	//           this.layout.Orientation = StackOrientation.Horizontal;
+	//           this.Content = this.layout;
+	//       }
+
+	//       public Color TextColor
+	//       {
+	//           get { return (Color)this.GetValue(TextColorProperty); }
+	//           set { this.SetValue(TextColorProperty, value); }
+	//       }
+
+	//       public string Text
+	//       {
+	//           get { return (string)this.GetValue(TextProperty); }
+	//           set { this.SetValue(TextProperty, value); }
+	//       }
+
+	//       public Color BoxColor
+	//       {
+	//           get { return (Color)this.GetValue(BoxColorProperty); }
+	//           set { this.SetValue(BoxColorProperty, value); }
+	//       }
+	//   } 
 }

Xamarin.Forms.Core.UnitTests/AppThemeTests.cs

@@ -0,0 +1,71 @@
+using System;
+using NUnit.Framework;
+
+namespace Xamarin.Forms.Core.UnitTests
+{
+	public class AppThemeTests : BaseTestFixture
+	{
+		[SetUp]
+		public override void Setup()
+		{
+			base.Setup();
+			Application.Current = new MockApplication();
+
+			Device.SetFlags(new[] { ExperimentalFlags.AppThemeExperimental });
+		}
+
+		[Test]
+		public void ThemeChangeUsingSetAppThemeColor()
+		{
+			var label = new Label
+			{
+				Text = "Green on Light, Red on Dark"
+			};
+
+			label.SetAppThemeColor(Label.TextColorProperty, Color.Green, Color.Red);
+			Assert.AreEqual(Color.Green, label.TextColor);
+
+			SetAppTheme(OSAppTheme.Dark);
+
+			Assert.AreEqual(Color.Red, label.TextColor);
+		}
+
+		[Test]
+		public void ThemeChangeUsingSetAppTheme()
+		{
+			var label = new Label
+			{
+				Text = "Green on Light, Red on Dark"
+			};
+
+			label.SetOnAppTheme(Label.TextColorProperty, Color.Green, Color.Red);
+			Assert.AreEqual(Color.Green, label.TextColor);
+
+			SetAppTheme(OSAppTheme.Dark);
+
+			Assert.AreEqual(Color.Red, label.TextColor);
+		}
+
+		[Test]
+		public void ThemeChangeUsingSetBinding()
+		{
+			var label = new Label
+			{
+				Text = "Green on Light, Red on Dark"
+			};
+
+			label.SetBinding(Label.TextColorProperty, new OnAppTheme<Color> { Light = Color.Green, Dark = Color.Red });
+			Assert.AreEqual(Color.Green, label.TextColor);
+
+			SetAppTheme(OSAppTheme.Dark);
+
+			Assert.AreEqual(Color.Red, label.TextColor);
+		}
+
+		void SetAppTheme(OSAppTheme theme)
+		{
+			((MockPlatformServices)Device.PlatformServices).RequestedTheme = theme;
+			Application.Current.OnRequestedThemeChanged(new AppThemeChangedEventArgs(theme));
+		}
+	}
+}

Xamarin.Forms.Core.UnitTests/Xamarin.Forms.Core.UnitTests.csproj

@@ -238,6 +238,7 @@
     <Compile Include="FlexLayoutAlignSelfTests.cs" />
     <Compile Include="FlexOrderTests.cs" />
     <Compile Include="FontAttributeConverterUnitTests.cs" />
+    <Compile Include="AppThemeTests.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Xamarin.Forms.Core\Xamarin.Forms.Core.csproj">
@@ -249,7 +250,7 @@
       <Name>Xamarin.Forms.Maps</Name>
     </ProjectReference>
     <ProjectReference Include="..\Xamarin.Forms.Platform\Xamarin.Forms.Platform.csproj">
-      <Project>{67f9d3a8-f71e-4428-913f-c37ae82cdb24}</Project>
+      <Project>{D31A6537-ED9C-4EBD-B231-A8D4FE44126A}</Project>
       <Name>Xamarin.Forms.Platform</Name>
     </ProjectReference>
     <ProjectReference Include="..\Xamarin.Forms.Xaml\Xamarin.Forms.Xaml.csproj">
@@ -274,7 +275,7 @@
   <ItemGroup />
   <Target Name="_CopyNUnitTestAdapterFiles" AfterTargets="Build">
     <ItemGroup>
-      <_NUnitTestAdapterFiles Include="$(NuGetPackageRoot)NUnit3TestAdapter\%(Version)\build\net35\**" Condition="@(PackageReference -> '%(Identity)') == 'NUnit3TestAdapter'" InProject="False" />
+      <_NUnitTestAdapterFiles Include="$(NuGetPackageRoot)NUnit3TestAdapter\%(Version)\build\net35\**" Condition="@(PackageReference -&gt; '%(Identity)') == 'NUnit3TestAdapter'" InProject="False" />
     </ItemGroup>
     <Copy SourceFiles="@(_NUnitTestAdapterFiles)" DestinationFolder="$(SolutionDir)packages\NUnitTestAdapter.AnyVersion\tools\%(RecursiveDir)" ContinueOnError="true" Retries="0" />
     <Copy SourceFiles="@(_NUnitTestAdapterFiles)" DestinationFolder="$(SolutionDir)packages\NUnitTestAdapter.AnyVersion\build\%(RecursiveDir)" ContinueOnError="true" Retries="0" />

Xamarin.Forms.Core/Application.cs

@@ -6,8 +6,6 @@
 using System.Threading.Tasks;
 using Xamarin.Forms.Internals;
 using Xamarin.Forms.Platform;
-using System.Diagnostics;
-using Xamarin.Forms.Core;
 
 namespace Xamarin.Forms
 {
@@ -59,7 +57,7 @@ public IAppLinks AppLinks
 		}
 
 		[EditorBrowsable(EditorBrowsableState.Never)]
-		public static void SetCurrentApplication(Application value) => Current = value; 
+		public static void SetCurrentApplication(Application value) => Current = value;
 
 		public static Application Current { get; set; }
 
@@ -161,18 +159,36 @@ public ResourceDictionary Resources
 
 		public event EventHandler<AppThemeChangedEventArgs> RequestedThemeChanged
 		{
-			add
-			{
-				ExperimentalFlags.VerifyFlagEnabled(nameof(Application), ExperimentalFlags.AppThemeExperimental, nameof(RequestedThemeChanged));
-
-				_weakEventManager.AddEventHandler(value);
-			}
+			add => _weakEventManager.AddEventHandler(value);
 			remove => _weakEventManager.RemoveEventHandler(value);
 		}
 
+		bool _themeChangedFiring;
+		OSAppTheme _lastAppTheme;
+
 		[EditorBrowsable(EditorBrowsableState.Never)]
 		public void OnRequestedThemeChanged(AppThemeChangedEventArgs args)
-			=> _weakEventManager.HandleEvent(this, args, nameof(RequestedThemeChanged));
+		{
+			if (Device.Flags.IndexOf(ExperimentalFlags.AppThemeExperimental) == -1)
+				return;
+
+			// On iOS the event is triggered more than once.
+			// To minimize that for us, we only do it when the theme actually changes and it's not currently firing
+			if (!_themeChangedFiring && RequestedTheme != _lastAppTheme)
+			{
+				try
+				{
+					_themeChangedFiring = true;
+					_lastAppTheme = RequestedTheme;
+
+					_weakEventManager.HandleEvent(this, args, nameof(RequestedThemeChanged));
+				}
+				finally
+				{
+					_themeChangedFiring = false;
+				}
+			}
+		}
 
 		public event EventHandler<ModalPoppedEventArgs> ModalPopped;