Control.QueryAccessibilityHelp Control.QueryAccessibilityHelp Control.QueryAccessibilityHelp Control.QueryAccessibilityHelp Event

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创建一个具有辅助功能的图表控件,并使用AccessibleObjectControl.ControlAccessibleObject类,以公开访问的信息。The following code example demonstrates the creation of an accessibility-aware chart control, using the AccessibleObject and Control.ControlAccessibleObject classes to expose accessible information. 控件绘制图例以及两条曲线。The control plots two curves along with a legend. ChartControlAccessibleObject类,该类派生自ControlAccessibleObject,在使用CreateAccessibilityInstance方法以提供自定义访问图表控件的信息。The ChartControlAccessibleObject class, which derives from ControlAccessibleObject, is used in the CreateAccessibilityInstance method to provide custom accessible information for the chart control. 因为不是实际图表图例Control-基于控制,但改为绘制由图表控件,它不提供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CurveLegendAccessibleObject,它表示每个部分的图例可访问信息。Because of this, the ChartControlAccessibleObject class overrides the GetChild method to return the CurveLegendAccessibleObject that represents accessible information for each part of the legend. 当辅助功能的应用程序使用该控件时,该控件可以提供所需的可访问信息。When an accessible-aware application uses this control, the control can provide the necessary accessible information.

这段代码摘录演示了如何处理QueryAccessibilityHelp事件。This code excerpt demonstrates handling the QueryAccessibilityHelp event. 请参阅AccessibleObject完整的代码示例的类概述。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

应使用HelpProvider类,以使用户能够通过按 F1 键来调用可访问对象的帮助。You should use the HelpProvider class to enable users to invoke help on your accessible object by pressing the F1 key. 使用HelpProvider中的完整信息为您提供QueryAccessibilityHelpEventArgsUsing 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