AutomationProperties.LiveSetting 在 .NET Framework 4.7.1 中的 WPF 中不起作用 [英] AutomationProperties.LiveSetting not working in WPF in .NET Framework 4.7.1

问题描述

我有一个 TextBlock，我想从屏幕阅读器跟踪该控件，每当在代码中为控件设置新值时，屏幕阅读器都应读出新文本.这在 .NET 框架 4.7.1 的 WPF 中可用，在 MSDN 链接.

I have a TextBlock and I want to track that control from Screen reader and whenever a new value is set to the control in code, the screen reader should readout the new text. This is available in WPF from .NET framework 4.7.1 which is mentioned in the MSDN LINK.

但对于 AutomationPeer 值，我总是得到 null.我在代码中缺少什么?我是否以正确的方式做这件事?请帮忙.

But I am always getting null for the AutomationPeer value. What am I missing in the code? Am I doing it in the right way? Please help.

XMAL

      <Window x:Class="WPFAccessibility.MainWindow"
                xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                xmlns:local="clr-namespace:WPFAccessibility"
                mc:Ignorable="d"
                Title="WPFAccessibility" Height="450" Width="800">
            <Grid>

                <TextBlock Name="MyTextBlock" AutomationProperties.LiveSetting="Assertive">My initial text</TextBlock>

                <Button Name="Save" Content="Save" HorizontalAlignment="Left" VerticalAlignment="Top" Width="75" Margin="50,321,0,0" Height="49" Click="Save_Click"/>   

            </Grid>
        </Window>

代码

 private void Save_Click(object sender, RoutedEventArgs e)
        {
            // Setting the MyTextBlock text to some other value and screen 
            // reader should notify to the user
            MyTextBlock.Text = "My changed text";
            var peer = UIElementAutomationPeer.FromElement(MyTextBlock); 
           // I am always getting peer value null 
            peer.RaiseAutomationEvent(AutomationEvents.LiveRegionChanged);
        }

推荐答案

使用 CreatePeerForElement 方法为 TextBlock 创建一个 UIElementAutomationPeer :

Use the CreatePeerForElement method to create a UIElementAutomationPeer for the TextBlock:

private void Save_Click(object sender, RoutedEventArgs e)
{
    MyTextBlock.Text = "My changed text";
    var peer = UIElementAutomationPeer.FromElement(MyTextBlock);
    if (peer == null)
        peer = UIElementAutomationPeer.CreatePeerForElement(MyTextBlock);
    peer.RaiseAutomationEvent(AutomationEvents.LiveRegionChanged);
}

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