Control.QueryAccessibilityHelp 事件

定义

AccessibleObject 为辅助功能应用程序提供帮助时发生。Occurs when AccessibleObject is providing help to accessibility applications.

public:
 event System::Windows::Forms::QueryAccessibilityHelpEventHandler ^ QueryAccessibilityHelp;
public event System.Windows.Forms.QueryAccessibilityHelpEventHandler QueryAccessibilityHelp;
member this.QueryAccessibilityHelp : System.Windows.Forms.QueryAccessibilityHelpEventHandler 
Public Custom Event QueryAccessibilityHelp As QueryAccessibilityHelpEventHandler 

示例

下面的代码示例演示如何使用 AccessibleObjectControl.ControlAccessibleObject 类创建可访问感知的图表控件,以公开辅助性信息。The following code example demonstrates the creation of an accessibility-aware chart control, using the AccessibleObject and Control.ControlAccessibleObject classes to expose accessible information. 控件将两条曲线与图例一起绘制。The control plots two curves along with a legend. ControlAccessibleObject派生的 ChartControlAccessibleObject 类在 CreateAccessibilityInstance 方法中用于为图表控件提供自定义的可访问信息。The ChartControlAccessibleObject class, which derives from ControlAccessibleObject, is used in the CreateAccessibilityInstance method to provide custom accessible information for the chart control. 由于图表图例不是实际的基于 Control 的控件,而是由图表控件绘制,因此它不具有任何内置的可访问信息。Since the chart legend is not an actual Control -based control, but instead is drawn by the chart control, it does not any built-in accessible information. 因此,ChartControlAccessibleObject 类将重写 GetChild 方法,以返回表示图例的每个部分可访问信息的 CurveLegendAccessibleObjectBecause of this, the ChartControlAccessibleObject class overrides the GetChild method to return the CurveLegendAccessibleObject that represents accessible information for each part of the legend. 当可访问感知的应用程序使用此控件时,控件可以提供必需的可访问信息。When an accessible-aware application uses this control, the control can provide the necessary accessible information.

此代码摘录演示如何处理 QueryAccessibilityHelp 事件。This code excerpt demonstrates handling the QueryAccessibilityHelp event. 有关完整的代码示例,请参阅 AccessibleObject 类概述。See the AccessibleObject class overview for the complete code example.

// Handles the QueryAccessibilityHelp event.
void ChartControl_QueryAccessibilityHelp( Object^ /*sender*/, System::Windows::Forms::QueryAccessibilityHelpEventArgs^ e )
{
   e->HelpString = "Displays chart data";
}
// Handles the QueryAccessibilityHelp event.
private void ChartControl_QueryAccessibilityHelp(object sender, 
                            System.Windows.Forms.QueryAccessibilityHelpEventArgs e)
{            
    e.HelpString = "Displays chart data";
}          
' Handle the QueryAccessibilityHelp event.
Private Sub ChartControl_QueryAccessibilityHelp(sender As Object, _
                   e As System.Windows.Forms.QueryAccessibilityHelpEventArgs) Handles MyBase.QueryAccessibilityHelp
    e.HelpString = "Displays chart data"
End Sub 

注解

你应使用 HelpProvider 类,使用户能够通过按 F1 键来调用辅助性对象上的帮助。You should use the HelpProvider class to enable users to invoke help on your accessible object by pressing the F1 key. 使用 HelpProvider 提供 QueryAccessibilityHelpEventArgs中的完整信息。Using the HelpProvider provides you with complete information in the QueryAccessibilityHelpEventArgs. 有关处理事件的详细信息,请参阅处理和引发事件For more information about handling events, see Handling and Raising Events.

适用于

另请参阅