AccessibleNavigation Enumeration
Assembly: System.Windows.Forms (in system.windows.forms.dll)
| Member name | Description | |
|---|---|---|
| Down | Navigation to a sibling object located below the starting object. | |
| FirstChild | Navigation to the first child of the object. | |
| LastChild | Navigation to the last child of the object. | |
| Left | Navigation to the sibling object located to the left of the starting object. | |
| Next | Navigation to the next logical object, typically from a sibling object to the starting object. | |
| Previous | Navigation to the previous logical object, typically from a sibling object to the starting object. | |
| Right | Navigation to the sibling object located to the right of the starting object. | |
| Up | Navigation to a sibling object located above the starting object. |
Accessible navigation directions are either spatial (up, down, left, and right) or logical (first child, last child, next, and previous). Logical directions are used when clients navigate from one user interface element to another within the same container.
AccessibleObject uses this enumeration.
For more information about the accessibility application, search for the "Microsoft Active Accessibility" topic in the MSDN library.
The following code example demonstrates the creation of an accessibility-aware chart control, using the AccessibleObject and Control.ControlAccessibleObject classes to expose accessible information. The control plots two curves along with a legend. The ChartControlAccessibleObject class, which derives from ControlAccessibleObject, is used in the CreateAccessibilityInstance method to provide custom accessible information for the chart control. 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. Because of this, the ChartControlAccessibleObject class overrides the GetChild method to return the CurveLegendAccessibleObject that represents accessible information for each part of the legend. When an accessible-aware application uses this control, the control can provide the necessary accessible information.
This example demonstrates using the AccessibleNavigation enumeration with the Navigate method. See the AccessibleObject class overview for the complete code example.
' Inner Class ChartControlAccessibleObject represents accessible information ' associated with the ChartControl. ' The ChartControlAccessibleObject is returned in the ' ChartControl.CreateAccessibilityInstance override. Public Class ChartControlAccessibleObject Inherits Control.ControlAccessibleObject Private chartControl As ChartControl Public Sub New(ctrl As ChartControl) MyBase.New(ctrl) chartControl = ctrl End Sub 'New ' Get the role for the Chart. This is used by accessibility programs. Public Overrides ReadOnly Property Role() As AccessibleRole Get Return System.Windows.Forms.AccessibleRole.Chart End Get End Property ' Get the state for the Chart. This is used by accessibility programs. Public Overrides ReadOnly Property State() As AccessibleStates Get Return AccessibleStates.ReadOnly End Get End Property ' The CurveLegend objects are "child" controls in terms of accessibility so ' return the number of ChartLengend objects. Public Overrides Function GetChildCount() As Integer Return chartControl.Legends.Length End Function ' Get the Accessibility object of the child CurveLegend idetified by index. Public Overrides Function GetChild(index As Integer) As AccessibleObject If index >= 0 And index < chartControl.Legends.Length Then Return chartControl.Legends(index).AccessibilityObject End If Return Nothing End Function ' Helper function that is used by the CurveLegend's accessibility object ' to navigate between sibiling controls. Specifically, this function is used in ' the CurveLegend.CurveLegendAccessibleObject.Navigate function. Friend Function NavigateFromChild(child As CurveLegend.CurveLegendAccessibleObject, _ navdir As AccessibleNavigation) As AccessibleObject Select Case navdir Case AccessibleNavigation.Down, AccessibleNavigation.Next Return GetChild(child.ID + 1) Case AccessibleNavigation.Up, AccessibleNavigation.Previous Return GetChild(child.ID - 1) End Select Return Nothing End Function ' Helper function that is used by the CurveLegend's accessibility object ' to select a specific CurveLegend control. Specifically, this function is used ' in the CurveLegend.CurveLegendAccessibleObject.Select function. Friend Sub SelectChild(child As CurveLegend.CurveLegendAccessibleObject, selection As AccessibleSelection) Dim childID As Integer = child.ID ' Determine which selection action should occur, based on the ' AccessibleSelection value. If (selection And AccessibleSelection.TakeSelection) <> 0 Then Dim i As Integer For i = 0 To chartControl.Legends.Length - 1 If i = childID Then chartControl.Legends(i).Selected = True Else chartControl.Legends(i).Selected = False End If Next i ' AccessibleSelection.AddSelection means that the CurveLegend will be selected. If (selection And AccessibleSelection.AddSelection) <> 0 Then chartControl.Legends(childID).Selected = True End If ' AccessibleSelection.AddSelection means that the CurveLegend will be unselected. If (selection And AccessibleSelection.RemoveSelection) <> 0 Then chartControl.Legends(childID).Selected = False End If End If End Sub 'SelectChild End Class 'ChartControlAccessibleObject
// Inner class ChartControlAccessibleObject represents accessible
// information associated with the ChartControl.
// The ChartControlAccessibleObject is returned in the
// ChartControl.CreateAccessibilityInstance override.
public static class ChartControlAccessibleObject
extends ControlAccessibleObject
{
private ChartControl chartControl;
public ChartControlAccessibleObject(ChartControl ctrl)
{
super(ctrl);
chartControl = ctrl;
} //ChartControlAccessibleObject
// Gets the role for the Chart. This is used by accessibility programs.
/** @property
*/
public AccessibleRole get_Role()
{
return AccessibleRole.Chart;
} //get_Role
// Gets the state for the Chart. This is used by accessibility programs.
/** @property
*/
public AccessibleStates get_State()
{
return AccessibleStates.ReadOnly;
} //get_State
// The CurveLegend objects are "child" controls in terms of
// accessibility so return the number of ChartLengend objects.
public int GetChildCount()
{
return chartControl.get_Legends().get_Length();
} //GetChildCount
// Gets the Accessibility object of the child CurveLegend
// idetified by index.
public AccessibleObject GetChild(int index)
{
if (index >= 0 && index < chartControl.get_Legends().get_Length()) {
return chartControl.get_Legends()[index].
get_AccessibilityObject();
}
return null;
} //GetChild
// Helper function that is used by the CurveLegend's accessibility
// object to navigate between sibiling controls.
// Specifically, this function is used in
// the CurveLegend.CurveLegendAccessibleObject.Navigate function.
AccessibleObject NavigateFromChild(
CurveLegend.CurveLegendAccessibleObject child,
AccessibleNavigation navDir)
{
if (navDir.Equals(AccessibleNavigation.Down)
|| navDir.Equals(AccessibleNavigation.Next)) {
return GetChild(child.get_ID() + 1);
}
else {
if (navDir.Equals(AccessibleNavigation.Up)
|| navDir.Equals(AccessibleNavigation.Previous)) {
return GetChild(child.get_ID() - 1);
}
}
return null;
} //NavigateFromChild
// Helper function that is used by the CurveLegend's accessibility
// object to select a specific CurveLegend control.
// Specifically, this function is used
// in the CurveLegend.CurveLegendAccessibleObject.Select function.
public void SelectChild(CurveLegend.CurveLegendAccessibleObject child,
AccessibleSelection selection)
{
int childID = child.get_ID();
// Determine which selection action should occur, based on the
// AccessibleSelection value.
if (Convert.ToInt32(selection & AccessibleSelection.TakeSelection)
!= 0) {
for (int i = 0; i < chartControl.get_Legends().get_Length();
i++) {
if (i == childID) {
((CurveLegend)chartControl.get_Legends().get_Item(i)).
set_Selected(true);
}
else {
((CurveLegend)chartControl.get_Legends().get_Item(i)).
set_Selected(false);
}
}
// AccessibleSelection.AddSelection means that the CurveLegend
// will be selected.
if (Convert.ToInt32(selection & AccessibleSelection.AddSelection)
!= 0) {
((CurveLegend)chartControl.get_Legends().get_Item(childID)).
set_Selected(true);
}
// AccessibleSelection.AddSelection means that the CurveLegend
// will be unselected.
if (Convert.ToInt32(selection &
AccessibleSelection.RemoveSelection) != 0) {
((CurveLegend)chartControl.get_Legends().get_Item(childID)).
set_Selected(false);
}
}
} //SelectChild
} //ChartControlAccessibleObject
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.