Visual.AddVisualChild(Visual) Method

Definition

Define la relación primario-secundario entre dos objetos visuales.Defines the parent-child relationship between two visuals.

protected:
 void AddVisualChild(System::Windows::Media::Visual ^ child);
protected void AddVisualChild (System.Windows.Media.Visual child);
member this.AddVisualChild : System.Windows.Media.Visual -> unit
Protected Sub AddVisualChild (child As Visual)

Parameters

child
Visual

Objeto visual secundario que se va a agregar al objeto visual primario.The child visual object to add to parent visual.

Examples

En el ejemplo siguiente se muestra cómo definir los requisitos de almacenamiento personalizados para un elemento secundario visual.The following example shows how to define custom storage requirements for a visual child. En el ejemplo se usan los métodos AddVisualChild y RemoveVisualChild para configurar la relación de elementos primarios y secundarios entre el objeto visual primario y el child.The example uses the AddVisualChild and RemoveVisualChild methods to sets up the parent-child relationship between the parent visual and child. Para que el árbol visual se Enumere correctamente, el ejemplo proporciona implementaciones invalidadas del método GetVisualChild y de VisualChildrenCount propiedad.In order for the visual tree to be enumerated correctly, the example provides overridden implementations of the GetVisualChild method and VisualChildrenCount property.

Note

Aunque es posible usar VisualCollection para crear relaciones de elementos primarios y secundarios entre objetos visuales, es más eficaz proporcionar su propia implementación de almacenamiento personalizada cuando solo se vincula un elemento secundario a un elemento primario.Although it is possible to use VisualCollection to create parent-child relationships between visual objects, it is more efficient to provide your own custom storage implementation when only one child is linked to a parent.

// Create a host visual derived from the FrameworkElement class.
// This class provides layout, event handling, and container support for
// the child visual object.
public class MyVisualHost : FrameworkElement
{
    private DrawingVisual _child;

    public MyVisualHost(DrawingVisual drawingVisual)
    {
        _child = drawingVisual;
        this.AddVisualChild(_child);
    }

    public DrawingVisual Child
    {
        get
        {
            return _child;
        }

        set
        {
            if (_child != value)
            {
                this.RemoveVisualChild(_child);
                _child = value;
                this.AddVisualChild(_child);
            }
        }
    }

    // Provide a required override for the VisualChildrenCount property.
    protected override int VisualChildrenCount
    {
        get { return _child == null ? 0 : 1; }
    }

    // Provide a required override for the GetVisualChild method.
    protected override Visual GetVisualChild(int index)
    {
        if (_child == null)
        {
            throw new ArgumentOutOfRangeException();
        }

        return _child;
    }
' Create a host visual derived from the FrameworkElement class.
' This class provides layout, event handling, and container support for
' the child visual object.
Public Class MyVisualHost
    Inherits FrameworkElement
    Private _child As DrawingVisual

    Public Sub New(ByVal drawingVisual As DrawingVisual)
        _child = drawingVisual
        Me.AddVisualChild(_child)
    End Sub

    Public Property Child() As DrawingVisual
        Get
            Return _child
        End Get

        Set(ByVal value As DrawingVisual)
            If _child IsNot value Then
                Me.RemoveVisualChild(_child)
                _child = value
                Me.AddVisualChild(_child)
            End If
        End Set
    End Property

    ' Provide a required override for the VisualChildrenCount property.
    Protected Overrides ReadOnly Property VisualChildrenCount() As Integer
        Get
            Return If(_child Is Nothing, 0, 1)
        End Get
    End Property

    ' Provide a required override for the GetVisualChild method.
    Protected Overrides Function GetVisualChild(ByVal index As Integer) As Visual
        If _child Is Nothing Then
            Throw New ArgumentOutOfRangeException()
        End If

        Return _child
    End Function

Remarks

El método AddVisualChild configura la relación de elementos primarios y secundarios entre dos objetos visuales.The AddVisualChild method sets up the parent-child relationship between two visual objects. Este método se debe usar cuando se necesita un control de bajo nivel más alto sobre la implementación de almacenamiento subyacente de objetos visuales secundarios.This method must be used when you need greater low-level control over the underlying storage implementation of visual child objects. VisualCollection se puede usar como una implementación predeterminada para almacenar objetos secundarios.VisualCollection can be used as a default implementation for storing child objects.

Applies to

See also