Visual.AddVisualChild(Visual) 方法

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

示例

下面的示例演示如何为视觉对象定义自定义存储要求。The following example shows how to define custom storage requirements for a visual child. 该示例使用AddVisualChild和RemoveVisualChild方法来设置父视觉对象和child之间的父子关系。The example uses the AddVisualChild and RemoveVisualChild methods to sets up the parent-child relationship between the parent visual and child. 为了正确枚举可视化树, 该示例提供GetVisualChild方法和VisualChildrenCount属性的重写实现。In order for the visual tree to be enumerated correctly, the example provides overridden implementations of the GetVisualChild method and VisualChildrenCount property.

// 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

AddVisualChild方法设置两个可视对象之间的父子关系。The AddVisualChild method sets up the parent-child relationship between two visual objects. 如果需要对可视子对象的基础存储实现进行更高级别的控制, 则必须使用此方法。This method must be used when you need greater low-level control over the underlying storage implementation of visual child objects. VisualCollection可用作存储子对象的默认实现。VisualCollection can be used as a default implementation for storing child objects.

适用于

另请参阅

• VisualCollection