How to make a screen device (JAWS) declare custom text when changing list items (WPF)?

Question

I have a WPF application that needs screen reader support (especially JAWS). The problem is that JAWS does not announce anything when the list view items have changed (added, deleted). And blind users are completely unaware of what happened. Can I somehow make the screen device announce the text when I try to add / remove an item from the list control? and how can i do this?

Answer 1

If the JAWS reader does not support this feature, you can implement it yourself with SpeechSynthesizer . Voice playback example:

 using System.Speech.Synthesis; SpeechSynthesizer MySpeechSynthesizer = new SpeechSynthesizer(); MySpeechSynthesizer.Speak("Hello!"); 

I used the ObservableCollection example to which the ListBox assigned. ObservableCollection is a CollectionChanged event that contains an enumeration of the actions performed on the [MSDN] collection:

 Member name Description ------------ ------------ Add One or more items were added to the collection. Move One or more items were moved within the collection. Remove One or more items were removed from the collection. Replace One or more items were replaced in the collection. Reset The content of the collection changed dramatically. 

This event will be implemented as follows:

 // Set the ItemsSource SampleListBox.ItemsSource = SomeListBoxCollection; // Set handler on the collection SomeListBoxCollection.CollectionChanged += new NotifyCollectionChangedEventHandler(SomeListBoxCollection_CollectionChanged); private void SomeListBoxCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e) { if (e.Action == NotifyCollectionChangedAction.Add) { // Some actions, in our case - speech } } 

Below is my example:

XAML

 <Window x:Class="JAWShelp.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525" WindowStartupLocation="CenterScreen"> <Grid> <ListBox Name="MyListBox" DisplayMemberPath="Name" SelectedIndex="0" Width="100" Height="100" Loaded="MyListBox_Loaded" /> <WrapPanel Width="200" Height="30" Margin="40,150,0,0"> <Button Name="AddButton" Padding="5" Content="Add item" VerticalAlignment="Bottom" Click="AddButton_Click" /> <Button Name="RemoveButton" Padding="5" Margin="30,0,0,0" Content="Remove item" VerticalAlignment="Bottom" Click="RemoveButton_Click" /> </WrapPanel> </Grid> </Window> 

Code behind

 // using System.Speech.Synthesis; // using System.Collections.ObjectModel; // using System.Collections.Specialized; public partial class MainWindow : Window { public class Person { public string Name { get; set; } } private ObservableCollection<Person> DataForListBox = new ObservableCollection<Person>(); public MainWindow() { InitializeComponent(); } private void MyListBox_Loaded(object sender, RoutedEventArgs e) { DataForListBox.Add(new Person() { Name = "Peter Orange", }); MyListBox.ItemsSource = DataForListBox; DataForListBox.CollectionChanged += new NotifyCollectionChangedEventHandler(DataForListBox_CollectionChanged); } private void DataForListBox_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e) { if (e.Action == NotifyCollectionChangedAction.Add) { SpeechSynthesizer MySpeechSynthesizer = new SpeechSynthesizer(); MySpeechSynthesizer.Speak("You are add item."); } if (e.Action == NotifyCollectionChangedAction.Remove) { SpeechSynthesizer MySpeechSynthesizer = new SpeechSynthesizer(); MySpeechSynthesizer.Speak("You are remove item."); } } private void AddButton_Click(object sender, RoutedEventArgs e) { DataForListBox.Add(new Person() { Name = "Jack Rider", }); } private void RemoveButton_Click(object sender, RoutedEventArgs e) { DataForListBox.RemoveAt(1); } } 

No problem, you can add play text to the Add/Remove element. You can also add a .wav play file using PromptBuilder :

 PromptBuilder MyPromptBuilder = new PromptBuilder(); MyPromptBuilder.AppendAudio("SomeFile.wav"); 

Answer 2

JAWS will only respond to controls that receive focus. I needed similar functionality in my application and resolved it with the following.

• Add two hidden text box controls to your layout.

   <!--Controls used to announce accessibility messages for screen readers.--> <TextBox x:Name="ATMessage_Silent" Height="1" Width="1" IsTabStop="False" AutomationProperties.Name=" "/> <TextBox x:Name="ATMessage_Audible" Height="1" Width="1" IsTabStop="False"/> 

• Add a class to declare messages. I found that in order to make it reliable, I needed to pause between the intermediate focus between several controls. Otherwise, JAWS does not reliably report messages.

   public class AccessibilityMessage { private AccessibilityMessage(object sender, string message, double delay) { DispatcherTimer sleep = new DispatcherTimer(); int counter = 3; try { if (accessibilityMessageAudibleControl != null && accessibilityMessageSilentControl != null) { sleep.Interval = TimeSpan.FromMilliseconds(delay); // Update the message. accessibilityMessageAudibleControl.SetValue(AutomationProperties.NameProperty, message); // Give focus to the silent control. accessibilityMessageSilentControl.IsTabStop = true; accessibilityMessageSilentControl.Focus(); // Give focus to the message. accessibilityMessageAudibleControl.IsTabStop = true; accessibilityMessageAudibleControl.Focus(); // Use a timer to simulate a sleep. We need to pause briefly to give enough time // for the screen reader to process the focus on the message control. After a brief // pause we will give focus back to the original control. If we do not pause like // this the screen reader will not reliably react to the message. sleep.Tick += (s, e) => { counter--; // Check to see if it is time to focus the original control. if (counter == 0) { // Return focus to the original control that triggered the message. if (sender != null && sender is Control) { // Give focus back to the original control. ((Control)sender).Focus(); } // Exit the timer. sleep.Stop(); // Inform any listeners the message has been announced. if (Announced != null) Announced(this, null); } }; // Start the time. sleep.Start(); } else { throw new Exception("Accessibility message controls are not defined in the Application Manager. Unable to announce accessibility message."); } } catch (Exception ex) { ErrorDialog.Show(ex, sender); } } public event EventHandler Announced; public static AccessibilityMessage Announce(object sender, string message, double delay = 250) { return new AccessibilityMessage(sender, message, delay); } } 

• Announce your posts. You can either simply make an announcement, or use the Announced event, which you can do, and then do additional work after the announcement.

  Make an announcement to tell the user to wait while the data grid is loaded with data.

   // Pass myGrid as the sender so it will receive focus after the announcement. ApplicationManager.AccessibilityMessage.Announce(myGrid, "Loading purchase orders table, please wait.").Announced += (s, arg) => { // MAKE WEB SERVICE CALL TO RETRIEVE DATA. DataService svc = new DataService(); svc.ListPurchasOrdersCompleted += OnListPurchaseOrders_Completed(); svc.ListPurchaseOrders(); }; 

  Announce that the data has been loaded into the data grid.

   private void OnListPurchaseOrders_Completed(object sender, AsyncCompletedEventArgs e) { try { if (e.Error == null) { myGrid.ItemsSource = e.Result(); // Pass myGrid as the sender so it will receive focus after the announcement. AccessibilityMessage.Announce(myGrid, string.Format("Loaded {0} orders into the purchase orders table.", myGrid.Items.Count)); } else { throw e.Error; } } catch (Exception ex) { ErrorDialog.Show(ex, this); } } 

Using this, you can make announcements whenever you want, just using the Announce () call. I originally implemented this for Silverlight. It should also work for WPF.