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可访问感知的图表控件, AccessibleObject并使用和Control.ControlAccessibleObject类公开可访问的信息。The following code example demonstrates the creation of an accessibility-aware chart control, using the AccessibleObject and Control.ControlAccessibleObject classes to expose accessible information. 控件将两条曲线与图例一起绘制。The control plots two curves along with a legend. CreateAccessibilityInstanceChartControlAccessibleObject 派生的类在方法中用于为图表控件提供自定义的可访问信息。ControlAccessibleObjectThe ChartControlAccessibleObject class, which derives from ControlAccessibleObject, is used in the CreateAccessibilityInstance method to provide custom accessible information for the chart control. 因为图表图例不是实际Control的控件,而是由图表控件绘制的,所以它不是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, ChartControlAccessibleObjectCurveLegendAccessibleObjectGetChild重写方法以返回,该方法表示图例的每个部分的可访问信息。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,请参阅类概述。AccessibleObjectSee 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. 使用可以QueryAccessibilityHelpEventArgs在中HelpProvider提供完整信息。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