Visual.AddVisualChild(Visual) 方法
定义
定义两个可视对象之间的父子关系。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)
参数
- child
- Visual
要添加到父可视对象的子可视对象。The child visual object to add to parent visual.
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.
备注
尽管可以使用VisualCollection创建可视对象之间的父子关系, 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。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
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.