IViewAutomationPeer Interface

Definition

Namespace:

System.Windows.Automation.Peers

Assembly:

PresentationFramework.dll

Allows a customized view of a ListView that derives from ViewBase to implement automation peer features that are specific to the custom view.

public interface class IViewAutomationPeer

public interface IViewAutomationPeer

type IViewAutomationPeer = interface

Public Interface IViewAutomationPeer

Derived

System.Windows.Automation.Peers.GridViewAutomationPeer

Examples

The following code shows a custom view implementing IViewAutomationPeer in a separate class to handle a button that appears at the top of the ListView control.

public class OneButtonHeaderView : ViewBase
{
    protected override IViewAutomationPeer GetAutomationPeer(ListView parent)
    {
        return new OneButtonHeaderViewAutomationPeer( this, parent );
    }

Public Class OneButtonHeaderView
    Inherits ViewBase
    Protected Overrides Function GetAutomationPeer(ByVal parent As ListView) As IViewAutomationPeer
        Return New OneButtonHeaderViewAutomationPeer(Me, parent)
    End Function

public class OneButtonHeaderViewAutomationPeer : IViewAutomationPeer
{
    ListView m_lv;

    public OneButtonHeaderViewAutomationPeer(OneButtonHeaderView control, ListView parent)
    {
        m_lv = parent;
    }

    ItemAutomationPeer IViewAutomationPeer.CreateItemAutomationPeer(Object item)
    {
        ListViewAutomationPeer lvAP = UIElementAutomationPeer.FromElement(m_lv) as ListViewAutomationPeer;
        return new ListBoxItemAutomationPeer(item, lvAP);
    }

    AutomationControlType IViewAutomationPeer.GetAutomationControlType()
    {
        return AutomationControlType.List;
    }

    List<AutomationPeer> IViewAutomationPeer.GetChildren(List<AutomationPeer> children)
    {
        // the children parameter is a list of automation peers for all the known items
        // our view must add its banner button peer to this list.

        Button b = (Button)m_lv.Template.FindName("BannerButton", m_lv);
        AutomationPeer peer = UIElementAutomationPeer.CreatePeerForElement(b);

        //If children is null, we still need to create an empty list to insert the button
        children ??= new List<AutomationPeer>();

        children.Insert(0, peer);

        return children;
    }

    Object IViewAutomationPeer.GetPattern(PatternInterface patternInterface)
    {
        // we can invoke the banner button 
        if (patternInterface == PatternInterface.Invoke)
        {
            Button b = (Button)m_lv.Template.FindName("BannerButton", m_lv);
            AutomationPeer peer = UIElementAutomationPeer.FromElement(b);
            if (peer != null)
                return peer;
        }

        // if this view does not have special handling for the pattern interface, return null
        // the ListViewAutomationPeer.GetPattern default handling will be used.
        return null;
    }

    void IViewAutomationPeer.ItemsChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e) { }

    void IViewAutomationPeer.ViewDetached() { }
}

Public Class OneButtonHeaderViewAutomationPeer
    Implements IViewAutomationPeer
    Private m_lv As ListView

    Public Sub New(ByVal control As OneButtonHeaderView, ByVal parent As ListView)
        m_lv = parent
    End Sub

    Private Function CreateItemAutomationPeer(ByVal item As Object) As ItemAutomationPeer Implements IViewAutomationPeer.CreateItemAutomationPeer
        Dim lvAP As ListViewAutomationPeer = TryCast(UIElementAutomationPeer.FromElement(m_lv), ListViewAutomationPeer)
        Return New ListBoxItemAutomationPeer(item, lvAP)
    End Function

    Private Function GetAutomationControlType() As AutomationControlType Implements IViewAutomationPeer.GetAutomationControlType
        Return AutomationControlType.List
    End Function

    Private Function GetChildren(ByVal children As List(Of AutomationPeer)) As List(Of AutomationPeer) Implements IViewAutomationPeer.GetChildren
        ' the children parameter is a list of automation peers for all the known items
        ' our view must add its banner button peer to this list.

        Dim b As Button = CType(m_lv.Template.FindName("BannerButton", m_lv), Button)
        Dim peer As AutomationPeer = UIElementAutomationPeer.CreatePeerForElement(b)

        'If children is null, we still need to create an empty list to insert the button
        If children Is Nothing Then
            children = New List(Of AutomationPeer)()
        End If

        children.Insert(0, peer)

        Return children
    End Function

    Private Function GetPattern(ByVal patternInterface As PatternInterface) As Object Implements IViewAutomationPeer.GetPattern
        ' we can invoke the banner button 
        If patternInterface = PatternInterface.Invoke Then
            Dim b As Button = CType(m_lv.Template.FindName("BannerButton", m_lv), Button)
            Dim peer As AutomationPeer = UIElementAutomationPeer.FromElement(b)
            If peer IsNot Nothing Then
                Return peer
            End If
        End If

        ' if this view does not have special handling for the pattern interface, return null
        ' the ListViewAutomationPeer.GetPattern default handling will be used.
        Return Nothing
    End Function

    Private Sub ItemsChanged(ByVal e As System.Collections.Specialized.NotifyCollectionChangedEventArgs) Implements IViewAutomationPeer.ItemsChanged
    End Sub

    Private Sub ViewDetached() Implements IViewAutomationPeer.ViewDetached
    End Sub
End Class

Methods

CreateItemAutomationPeer(Object)	Creates a new instance of the ItemAutomationPeer class.
GetAutomationControlType()	Gets the control type for the element that is associated with this IViewAutomationPeer.
GetChildren(List<AutomationPeer>)	Gets the collection of immediate child elements of the specified UI Automation peer.
GetPattern(PatternInterface)	Gets the control pattern that is associated with the specified patternInterface.
ItemsChanged(NotifyCollectionChangedEventArgs)	Called by ListView when the collection of items changes.
ViewDetached()	Called when the custom view is no longer applied to the ListView.

See also

• ViewBase
• GetAutomationPeer(ListView)