未调用Silverlight行为onDetaching覆盖

Question

我已经创建了一个自定义行为(没有混合)来拖动UIElements并获得你在光标下拖动的半透明缩略图(混合版本移动目标对象,这不是我需要的)

Anyhoo,代码实际上非常简单并且工作得很好,我遇到的问题是onDetaching()没有被调用,这意味着我对UIElement的事件没有解开.

这让我有点担心,因为我猜测行为没有脱离的唯一原因是因为它仍被某些东西引用.它不应该是UIElement它自己,因为我们在一个阶段有泄漏问题,但我们现在已经解决了它们,这通过WinDbg澄清.

关于它的唯一有趣(？)的事情是行为附加到项目控件中的图像,但这不应该有所作为吗？

这是我目前的代码:

public class DragBehavior : Behavior<UIElement>
{
    private const double DRAG_DISTANCE = 20;
    private const int DRAG_ICON_HEIGHT = 100;

    Point m_firstPoint;
    private bool m_isDragging = false;
    private Popup m_dragPopup = null;
    private Image m_draggedImage;        

    protected override void OnAttached()
    {
        this.AssociatedObject.MouseLeftButtonDown += new MouseButtonEventHandler(AssociatedObject_MouseLeftButtonDown);
        this.AssociatedObject.MouseMove += new MouseEventHandler(AssociatedObject_MouseMove);
        this.AssociatedObject.MouseLeftButtonUp += new MouseButtonEventHandler(AssociatedObject_MouseLeftButtonUp);

        base.OnAttached();
    }

    void AssociatedObject_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        m_firstPoint = e.GetPosition(null);
        m_isDragging = true;
    }

    void AssociatedObject_MouseMove(object sender, MouseEventArgs e)
    {
        if (m_isDragging)
        {
            Point currentPosition = e.GetPosition(null);

            if (m_dragPopup == null)
            {
                double deltaX = currentPosition.X - m_firstPoint.X;
                double deltaY = currentPosition.Y - m_firstPoint.Y;

                double movement = Math.Sqrt((deltaX * deltaX) + (deltaY * deltaY));
                if (movement > DRAG_DISTANCE)
                {
                    // Get a screen shot of the element this behaviour is attached to
                    WriteableBitmap elementScreenshot = new WriteableBitmap(AssociatedObject, null);

                    // Create an image out of it
                    m_draggedImage = new Image();
                    m_draggedImage.Height = DRAG_ICON_HEIGHT;
                    m_draggedImage.Stretch = Stretch.Uniform;
                    m_draggedImage.Source = elementScreenshot;
                    m_draggedImage.Opacity = 0.4;

                    // Add the image to the popup
                    m_dragPopup = new Popup();
                    m_dragPopup.Child = m_draggedImage;

                    m_dragPopup.IsOpen = true;
                    m_dragPopup.UpdateLayout();

                    m_dragPopup.HorizontalOffset = currentPosition.X - m_draggedImage.ActualWidth/2;
                    m_dragPopup.VerticalOffset = currentPosition.Y - m_draggedImage.ActualHeight/2;

                    AssociatedObject.CaptureMouse();
                }
            }
            else
            {
                m_dragPopup.HorizontalOffset = currentPosition.X - m_draggedImage.ActualWidth/2;
                m_dragPopup.VerticalOffset = currentPosition.Y - m_draggedImage.ActualHeight/2;
            }
        }
    }

    void AssociatedObject_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        if (m_isDragging == true && m_dragPopup != null)
        {
            m_isDragging = false;
            m_dragPopup.IsOpen = false;
            m_dragPopup = null;
        }

        AssociatedObject.ReleaseMouseCapture();

        GC.Collect();
        GC.WaitForPendingFinalizers();
        GC.Collect();
    }

    protected override void OnDetaching()
    {
        this.AssociatedObject.MouseLeftButtonDown -= new MouseButtonEventHandler(AssociatedObject_MouseLeftButtonDown);
        this.AssociatedObject.MouseMove -= new MouseEventHandler(AssociatedObject_MouseMove);
        this.AssociatedObject.MouseLeftButtonUp -= new MouseButtonEventHandler(AssociatedObject_MouseLeftButtonUp);

        base.OnDetaching();
    }
}

我知道有两篇帖子我见过这个...

这个 - forums.silverlight.net/forums/p/142038/317146.aspx没有帮助,因为我试图强制GC无济于事,而这一个 - 自动调用OnDetaching()为Silverlight行为我不真正得到他们的探索,因为他们声称它将UIElement挂钩到引起它的行为,但是当根引用UIElement被打破时,对行为的根引用也将被删除,因此两者都变得可以被GC接受.

我希望这很简单,但如果没有,我会开始使用WinDbg看看实际发生了什么!

任何帮助深表感谢!:)

谢谢,

安迪.

Answer 1

您没有显示从何处调用分离。需要实际调用 object.Detach() (DragBehavior) 才能调用 OnDetaching() 方法。

如果您想在 AssociatedObject_MouseLeftButtonUp 事件处理程序中分离它，您可以在方法末尾调用 detach，只要您确实不需要对其执行任何其他操作。

void AssociatedObject_MouseLeftButtonUp(object sender, MouseButtonEventArgs e) 
{ 
    if (m_isDragging == true && m_dragPopup != null) 
    { 
        m_isDragging = false; 
        m_dragPopup.IsOpen = false; 
        m_dragPopup = null; 
    } 

    AssociatedObject.ReleaseMouseCapture(); 

    this.Detach()
} 

我绝对不会对 GC 进行任何调用，这会对性能产生巨大影响。