Approach — How to send and resend accessibility focus

A11YTools.sln

@@ -141,6 +141,8 @@ Global
 		{DC93383E-CE5B-4B18-B3CD-39FFFA8B41DD}.Release|x86.Build.0 = Release|Any CPU
 		{DC93383E-CE5B-4B18-B3CD-39FFFA8B41DD}.Release|x86.Deploy.0 = Release|Any CPU
 		{365D53AD-E0C1-4119-8A2A-CCBF30E4440F}.Debug|Any CPU.ActiveCfg = Debug|x86
+		{365D53AD-E0C1-4119-8A2A-CCBF30E4440F}.Debug|Any CPU.Build.0 = Debug|x86
+		{365D53AD-E0C1-4119-8A2A-CCBF30E4440F}.Debug|Any CPU.Deploy.0 = Debug|x86
 		{365D53AD-E0C1-4119-8A2A-CCBF30E4440F}.Debug|ARM.ActiveCfg = Debug|ARM
 		{365D53AD-E0C1-4119-8A2A-CCBF30E4440F}.Debug|ARM.Build.0 = Debug|ARM
 		{365D53AD-E0C1-4119-8A2A-CCBF30E4440F}.Debug|ARM.Deploy.0 = Debug|ARM

A11YTools/A11YTools.Android/A11YTools.Android.csproj

@@ -58,6 +58,7 @@
     <PackageReference Include="Xamarin.Essentials" Version="1.5.3.2" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="AccessibleFocusBlockRenderer.cs" />
     <Compile Include="PlatformEffectBase.cs" />
     <Compile Include="NativeSemanticEffect.cs" />
     <Compile Include="SemanticViewRenderer.cs" />

A11YTools/A11YTools.Android/AccessibleFocusBlockRenderer.cs

@@ -0,0 +1,72 @@
+using A11YTools.UWP;
+using A11YTools.Views;
+using Android.Content;
+using Android.Views.Accessibility;
+using Xamarin.Forms;
+using Xamarin.Forms.Platform.Android;
+
+[assembly: ExportRenderer(typeof(AccessibleFocusBlock), typeof(AccessibleFocusBlockRenderer))]
+namespace A11YTools.UWP
+{
+    public class AccessibleFocusBlockRenderer : ViewRenderer<AccessibleFocusBlock, Android.Views.View>
+    {
+        private bool isFocused = false;
+
+        public AccessibleFocusBlockRenderer(Context context) : base(context)
+        {
+
+        }
+
+        protected override void OnElementChanged(ElementChangedEventArgs<AccessibleFocusBlock> e)
+        {
+            base.OnElementChanged(e);
+
+            if (e.NewElement != null)
+            {
+                FocusChange += Control_FocusChange;
+            }
+            else
+            {
+                FocusChange -= Control_FocusChange;
+            }
+        }
+
+        private void Control_FocusChange(object sender, FocusChangeEventArgs e)
+        {
+            if (e.HasFocus)
+            {
+                if (!isFocused)
+                    Element?.OnAccessibilityGotFocus();
+
+                isFocused = true;
+            }
+            else
+            {
+                if (isFocused)
+                    Element?.OnAccessibilityLostFocus();
+
+                isFocused = false;
+            }
+        }
+
+        public override void OnInitializeAccessibilityEvent(AccessibilityEvent e)
+        {
+            base.OnInitializeAccessibilityEvent(e);
+
+            if (e.EventType == EventTypes.ViewAccessibilityFocused)
+            {
+                if (!isFocused)
+                    Element?.OnAccessibilityGotFocus();
+
+                isFocused = true;
+            }
+            else if (e.EventType == EventTypes.ViewAccessibilityFocusCleared)
+            {
+                if (isFocused)
+                    Element?.OnAccessibilityLostFocus();
+
+                isFocused = false;
+            }
+        }
+    }
+}

A11YTools/A11YTools.Android/AndroidA11yService.cs

@@ -65,7 +65,7 @@ public void SetFocus(VisualElement element)
             var renderer = Platform.GetRenderer(element);
             var view = element.GetViewForAccessibility();
 
-            view?.SendAccessibilityEvent(EventTypes.ViewAccessibilityFocused);
+            view?.SendAccessibilityEvent(EventTypes.ViewFocused);
         }
 
         public void SetAnnouncement(string text)

A11YTools/A11YTools.UWP/A11YTools.UWP.csproj

@@ -90,6 +90,7 @@
     <UseDotNetNativeToolchain>true</UseDotNetNativeToolchain>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="AccessibleFocusBlockRenderer.cs" />
     <Compile Include="App.xaml.cs">
       <DependentUpon>App.xaml</DependentUpon>
     </Compile>
@@ -98,6 +99,7 @@
     </Compile>
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="SemanticViewRenderer.cs" />
+    <Compile Include="UWPA11yService.cs" />
   </ItemGroup>
   <ItemGroup>
     <AppxManifest Include="Package.appxmanifest">
@@ -162,4 +164,9 @@
     <VisualStudioVersion>14.0</VisualStudioVersion>
   </PropertyGroup>
   <Import Project="$(MSBuildExtensionsPath)\Microsoft\WindowsXaml\v$(VisualStudioVersion)\Microsoft.Windows.UI.Xaml.CSharp.targets" />
+  <ProjectExtensions>
+    <VisualStudio>
+      <UserProperties XamarinHotReloadXFormsNugetUpgradeInfoBarA11YToolsUWPHideInfoBar="True" />
+    </VisualStudio>
+  </ProjectExtensions>
 </Project>

A11YTools/A11YTools.UWP/AccessibleFocusBlockRenderer.cs

@@ -0,0 +1,81 @@
+using A11YTools.UWP;
+using A11YTools.Views;
+using System.ComponentModel;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Xamarin.Forms.Platform.UWP;
+
+[assembly: ExportRenderer(typeof(AccessibleFocusBlock), typeof(AccessibleFocusBlockRenderer))]
+namespace A11YTools.UWP
+{
+    public class AccessibleFocusBlockRenderer : ViewRenderer<AccessibleFocusBlock, Windows.UI.Xaml.Controls.Button>
+    {
+        private Windows.UI.Xaml.Controls.Button accessibilityHiddenBtn = null;
+
+        protected override void OnElementChanged(ElementChangedEventArgs<AccessibleFocusBlock> e)
+        {
+            base.OnElementChanged(e);
+
+            if (e.OldElement != null && accessibilityHiddenBtn != null)
+            {
+                accessibilityHiddenBtn.GotFocus -= AccessibilityHiddenBtn_GotFocus;
+                accessibilityHiddenBtn.LostFocus -= AccessibilityHiddenBtn_LostFocus;
+                accessibilityHiddenBtn = null;
+
+                SetNativeControl(null);
+            }
+
+            if (e.NewElement != null)
+            {
+                accessibilityHiddenBtn = new Windows.UI.Xaml.Controls.Button();
+                accessibilityHiddenBtn.IsTabStop = e.NewElement.IsTabStop;
+                accessibilityHiddenBtn.IsHitTestVisible = false;
+                accessibilityHiddenBtn.IsEnabled = false;
+                accessibilityHiddenBtn.Visibility = e.NewElement.IsTabStop && e.NewElement.IsEnabled && e.NewElement.IsVisible ? Visibility.Visible : Visibility.Collapsed;
+                accessibilityHiddenBtn.UseSystemFocusVisuals = false;
+                accessibilityHiddenBtn.GotFocus += AccessibilityHiddenBtn_GotFocus;
+                accessibilityHiddenBtn.LostFocus += AccessibilityHiddenBtn_LostFocus;
+                Canvas.SetZIndex(accessibilityHiddenBtn, -1);
+
+                SetNativeControl(accessibilityHiddenBtn);
+            }
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing && Control != null)
+            {
+                accessibilityHiddenBtn.GotFocus -= AccessibilityHiddenBtn_GotFocus;
+                accessibilityHiddenBtn.LostFocus -= AccessibilityHiddenBtn_LostFocus;
+                accessibilityHiddenBtn = null;
+
+                SetNativeControl(null);
+            }
+            base.Dispose(disposing);
+        }
+
+        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
+        {
+            base.OnElementPropertyChanged(sender, e);
+
+            switch (e.PropertyName)
+            {
+                case nameof(Element.IsEnabled):
+                case nameof(Element.IsTabStop):
+                case nameof(Element.IsVisible):
+                    accessibilityHiddenBtn.Visibility = Element.IsTabStop && Element.IsEnabled && Element.IsVisible ? Visibility.Visible : Visibility.Collapsed;
+                    break;
+            }
+        }
+
+        private void AccessibilityHiddenBtn_GotFocus(object sender, RoutedEventArgs e)
+        {
+            Element?.OnAccessibilityGotFocus();
+        }
+
+        private void AccessibilityHiddenBtn_LostFocus(object sender, RoutedEventArgs e)
+        {
+            Element?.OnAccessibilityLostFocus();
+        }
+    }
+}

A11YTools/A11YTools.UWP/UWPA11yService.cs

@@ -0,0 +1,52 @@
+using A11YTools.UWP;
+using A11YTools.Views;
+using System;
+using System.Diagnostics;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Input;
+using Xamarin.Forms;
+using Xamarin.Forms.Platform.UWP;
+
+[assembly: Dependency(typeof(UWPA11yService))]
+namespace A11YTools.UWP
+{
+    public class UWPA11yService : IA11yService
+    {
+        public void SetAnnouncement(string text)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void SetControlType(VisualElement element, ControlType controlType)
+        {
+            throw new NotImplementedException();
+        }
+
+        public async void SetFocus(VisualElement element)
+        {
+            var containerElement = Platform.GetRenderer(element).ContainerElement;
+
+            FrameworkElement view = null;
+            if (containerElement is AccessibleFocusBlockRenderer)
+            {
+                view = ((Xamarin.Forms.Platform.UWP.VisualElementRenderer<A11YTools.Views.AccessibleFocusBlock, Windows.UI.Xaml.Controls.Button>)containerElement).Control;
+            }
+            if (containerElement is ButtonRenderer)
+            {
+                view = ((VisualElementRenderer<Xamarin.Forms.Button, Xamarin.Forms.Platform.UWP.FormsButton>)containerElement).Control;
+            }
+
+            if (view == null)
+                throw new NotImplementedException();
+
+            var result = await FocusManager.TryFocusAsync(view, FocusState.Programmatic);
+
+            Debug.WriteLine($"Set focus result {result.Succeeded}");
+        }
+
+        public void SetIsClickable(VisualElement element, bool isClickable, Action clickActionThatOnlyRunsOnAndroid)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}

A11YTools/A11YTools/Views/AccessibleFocusBlock.cs

@@ -0,0 +1,17 @@
+using Xamarin.Forms;
+
+namespace A11YTools.Views
+{
+    public class AccessibleFocusBlock : ContentView
+    {
+        public virtual void OnAccessibilityGotFocus()
+        {
+
+        }
+
+        public virtual void OnAccessibilityLostFocus()
+        {
+
+        }
+    }
+}

A11YTools/A11YTools/Views/SetFocus.xaml

@@ -1,15 +1,45 @@
 <?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="A11YTools.Views.SetFocus">
+             x:Class="A11YTools.Views.SetFocus"
+             xmlns:local="clr-namespace:A11YTools.Views">
     <ContentPage.Content>
+
         <StackLayout>
-            <Label x:Name="theLabel" Text="Hello I am the Label"></Label>
-            <Button
-                Text="Set Accessibility Focus To Label"
-                Clicked="Button_Clicked"
-                VerticalOptions="CenterAndExpand" 
-                HorizontalOptions="CenterAndExpand" />
+
+            <local:AccessibleFocusBlock x:Name="afcLabel" 
+                                        AutomationProperties.IsInAccessibleTree="True"
+                                        AutomationProperties.LabeledBy="{x:Reference theLabel}">
+                <Label x:Name="theLabel" 
+                       Text="Hello I am the Label" />
+            </local:AccessibleFocusBlock>
+
+            <local:AccessibleFocusBlock x:Name="afcLabel2"
+                                        AutomationProperties.IsInAccessibleTree="True"
+                                        AutomationProperties.LabeledBy="{x:Reference theLabel2}">
+                <Label x:Name="theLabel2" 
+                       Text="Hello I am the Label 2" />
+            </local:AccessibleFocusBlock>
+
+            <Button x:Name="theButton1"
+                    Text="Set Accessibility Focus To Label"
+                    Clicked="Button_Clicked"
+                    VerticalOptions="CenterAndExpand" 
+                    HorizontalOptions="CenterAndExpand" />
+
+            <Button x:Name="theButton2"
+                    Text="Set Accessibility Focus To Label 2"
+                    Clicked="Button2_Clicked"
+                    VerticalOptions="CenterAndExpand" 
+                    HorizontalOptions="CenterAndExpand" />
+
+            <Button x:Name="theButton3"
+                    Text="Set Accessibility Focus To Button 1"
+                    Clicked="Button3_Clicked"
+                    VerticalOptions="CenterAndExpand" 
+                    HorizontalOptions="CenterAndExpand" />
+
         </StackLayout>
+
     </ContentPage.Content>
 </ContentPage>

A11YTools/A11YTools/Views/SetFocus.xaml.cs

@@ -1,8 +1,4 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 using Xamarin.Forms;
 using Xamarin.Forms.Xaml;
@@ -21,7 +17,16 @@ public SetFocus()
 
         private void Button_Clicked(object sender, EventArgs e)
         {
-            _a11yService.SetFocus(theLabel);
+            _a11yService.SetFocus(afcLabel);
+        }
+        private void Button2_Clicked(object sender, EventArgs e)
+        {
+            _a11yService.SetFocus(afcLabel2);
+        }
+
+        private void Button3_Clicked(object sender, EventArgs e)
+        {
+            _a11yService.SetFocus(theButton1);
         }
     }
 }