在 UI 自动化片段提供程序中启用导航
备注
本文档适用于想要使用 System.Windows.Automation 命名空间中定义的托管 UI 自动化类的 .NET Framework 开发人员。 有关 UI 自动化的最新信息，请参阅 Windows 自动化 API：UI 自动化。
本主题包含示例代码，该示例代码演示如何为片段中的元素启用在 UI 自动化提供程序中导航的功能。
示例
下面的示例代码为列表中的列表项实现 Navigate 父元素是列表框元素，且同级元素是列表集合中的其他项。 对于无效的方向，该方法返回 null （在 Visual Basic 中则返回Nothing ）；在本例中，将返回 FirstChild 和 LastChild，因为该元素没有任何子级。
/// <summary>
/// Navigate to adjacent elements in the automation tree.
/// </summary>
/// <param name="direction">Direction to navigate.</param>
/// <returns>The element in that direction, or null.</returns>
/// <remarks>
/// parentControl is the provider for the list box.
/// parentItems is the collection of list item providers.
/// </remarks>
public IRawElementProviderFragment Navigate(NavigateDirection direction)
{
int myIndex = parentItems.IndexOf(this);
if (direction == NavigateDirection.Parent)
{
return (IRawElementProviderFragment)parentControl;
}
else if (direction == NavigateDirection.NextSibling)
{
if (myIndex < parentItems.Count - 1)
{
return (IRawElementProviderFragment)parentItems[myIndex + 1];
}
else
{
return null;
}
}
else if (direction == NavigateDirection.PreviousSibling)
{
if (myIndex > 0)
{
return (IRawElementProviderFragment)parentItems[myIndex - 1];
}
else
{
return null;
}
}
else
{
return null;
}
}
''' <summary>
''' Navigate to adjacent elements in the automation tree.
''' </summary>
''' <param name="direction">Direction to navigate.</param>
''' <returns>The element in that direction, or null.</returns>
''' <remarks>
''' parentControl is the provider for the list box.
''' parentItems is the collection of list item providers.
''' </remarks>
Public Function Navigate(ByVal direction As NavigateDirection) As IRawElementProviderFragment _
Implements IRawElementProviderFragment.Navigate
Dim myIndex As Integer = parentItems.IndexOf(Me)
If direction = NavigateDirection.Parent Then
Return DirectCast(parentControl, IRawElementProviderFragment)
ElseIf direction = NavigateDirection.NextSibling Then
If myIndex < parentItems.Count - 1 Then
Return DirectCast(parentItems((myIndex + 1)), IRawElementProviderFragment)
Else
Return Nothing
End If
ElseIf direction = NavigateDirection.PreviousSibling Then
If myIndex > 0 Then
Return DirectCast(parentItems((myIndex - 1)), IRawElementProviderFragment)
Else
Return Nothing
End If
Else
Return Nothing
End If
End Function 'Navigate