ContainerVisual.GetVisualChild(Int32) 方法

定义

命名空间:

System.Windows.Media

程序集:

PresentationCore.dll

返回父级 ContainerVisual 指定的子级 Visual。

protected:
 override System::Windows::Media::Visual ^ GetVisualChild(int index);

protected override sealed System.Windows.Media.Visual GetVisualChild (int index);

override this.GetVisualChild : int -> System.Windows.Media.Visual

Protected Overrides NotOverridable Function GetVisualChild (index As Integer) As Visual

参数

index

Int32

一个 32 位带符号整数，它表示子 Visual 的索引值。 index 的值必须介于 0 和 VisualChildrenCount - 1 之间。

返回

Visual

子级 Visual。

示例

以下示例演示如何创建用作两DrawingVisual个ContainerVisual对象的父对象。 ContainerVisual添加到对象的对象必须以反向 z 顺序添加到顶部 (顶部) ，以确保它们以正确的绘图顺序呈现。 为了使可视化树能够正确枚举，此示例提供重写的方法和VisualChildrenCount属性的实现GetVisualChild。

// Create a host visual derived from the FrameworkElement class.
// This class provides layout, event handling, and container support for
// the child visual objects.
public class MyContainerVisualHost : FrameworkElement
{
    private ContainerVisual _containerVisual;

    public MyContainerVisualHost(DrawingVisual border, DrawingVisual text)
    {
        // Create a ContainerVisual to hold DrawingVisual children.
        _containerVisual = new ContainerVisual();

        // Add children to ContainerVisual in reverse z-order (bottom to top).
        _containerVisual.Children.Add(border);
        _containerVisual.Children.Add(text);

        // Create parent-child relationship with host visual and ContainerVisual.
        this.AddVisualChild(_containerVisual);
    }

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

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

        return _containerVisual;
    }
}

' Create a host visual derived from the FrameworkElement class.
' This class provides layout, event handling, and container support for
' the child visual objects.
Public Class MyContainerVisualHost
    Inherits FrameworkElement
    Private _containerVisual As ContainerVisual

    Public Sub New(ByVal border As DrawingVisual, ByVal text As DrawingVisual)
        ' Create a ContainerVisual to hold DrawingVisual children.
        _containerVisual = New ContainerVisual()

        ' Add children to ContainerVisual in reverse z-order (bottom to top).
        _containerVisual.Children.Add(border)
        _containerVisual.Children.Add(text)

        ' Create parent-child relationship with host visual and ContainerVisual.
        Me.AddVisualChild(_containerVisual)
    End Sub

    ' Provide a required override for the VisualChildrenCount property.
    Protected Overrides ReadOnly Property VisualChildrenCount() As Integer
        Get
            Return If(_containerVisual 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 _containerVisual Is Nothing Then
            Throw New ArgumentOutOfRangeException()
        End If

        Return _containerVisual
    End Function
End Class

注解

默认情况下，没有 ContainerVisual 任何子级。

继承者说明

在此调用期间，无法修改可视化树。

另请参阅

• VisualChildrenCount