Visual.AddVisualChild(Visual) 方法

定義

命名空間:

System.Windows.Media

組件:

PresentationCore.dll

定義兩個視覺項目之間的父-子關係。

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)

參數

child

Visual

要加入至父視覺項目的子視覺物件。

範例

下列範例示範如何定義視覺子系的自訂儲存需求。 此範例會使用 AddVisualChild 和 RemoveVisualChild 方法來設定父視覺效果與 child 之間的父子式關聯性。 為了讓視覺化樹狀結構正確列舉，此範例會提供方法與 VisualChildrenCount 屬性的 GetVisualChild 覆寫實作。

注意

雖然可以使用 VisualCollection 在視覺物件之間建立父子式關聯性，但是當只有一個子系連結到父系時，提供您自己的自訂儲存體實作會更有效率。

// 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

備註

方法 AddVisualChild 會設定兩個視覺物件之間的父子關聯性。 當您需要對視覺子物件的基礎儲存實作進行更大的低階控制時，必須使用這個方法。 VisualCollection 可作為儲存子物件的預設實作。

另請參閱

• VisualCollection