Visual.AddVisualChild(Visual) 方法

定义

命名空间:

System.Windows.Media

程序集:

PresentationCore.dll

定义两个可视对象之间的父子关系。

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)

参数

child

Visual

要添加到父可视对象的子可视对象。

示例

以下示例演示如何为视觉对象子级定义自定义存储要求。 该示例使用 AddVisualChild 和 RemoveVisualChild 方法设置父视觉对象与 child之间的父子关系。 为了正确枚举可视化树，该示例提供了 方法和 VisualChildrenCount 属性的GetVisualChild重写实现。

注意

尽管可以使用 VisualCollection 在视觉对象之间创建父子关系，但当只有一个子级链接到父对象时，提供自己的自定义存储实现会更有效。

// 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

注解

方法 AddVisualChild 设置两个视觉对象之间的父子关系。 当需要对可视子对象的基础存储实现进行更高级别的控制时，必须使用此方法。 VisualCollection 可用作存储子对象的默认实现。

另请参阅

• VisualCollection