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Drag & Drop in TreeControl

Posted on 2003-03-19
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Last Modified: 2013-11-20
I have an MFC app in "explorer style" and I would like to implement a drag & drop functionality. That is if you drag an item in the tree view then I will perform certain actions.

The problem right now is that while I see the selected item while I move the mouse, the image being dragged is always only the first one I selected after I started the program.

Example, I have 5 tree items and after launching the app I select the 2nd item and drag it. I correctly see the image of the 2nd item being dragged. However if I select and drag the 4th item then I still will see the 2nd image - unless I restart the program.

I do delete the ImageList so I don't understand why this is happening. This is the code that I am using:

void CLeftView::OnBegindrag(NMHDR* pNMHDR, LRESULT* pResult)
{
     NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;

     bIsDragDrop = TRUE;

     CTreeCtrl& treeCtrl = GetTreeCtrl();
     HTREEITEM hSelectedNode = treeCtrl.GetSelectedItem();

     CPoint point;

     pImageList = treeCtrl.CreateDragImage(hSelectedNode);
     
     pImageList->BeginDrag(0, CPoint(0,0));
     pImageList->DragEnter(this, point);

     SetCapture();
     
     *pResult = 0;
}

void CLeftView::OnMouseMove(UINT nFlags, CPoint point)
{
     if (bIsDragDrop) {
          pImageList->DragMove(point);
     }
     
     CTreeView::OnMouseMove(nFlags, point);
}

void CLeftView::OnLButtonUp(UINT nFlags, CPoint point)
{
     if (bIsDragDrop) {
          bIsDragDrop = FALSE;

          ReleaseCapture();
          pImageList->DragLeave(this);

            // "delete pImageList;" yields the same result
          pImageList->DeleteImageList();
          ASSERT(pImageList->GetSafeHandle() == NULL);
     }
     
     CTreeView::OnLButtonUp(nFlags, point);
}


Thank you.
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Question by:FlorianJaeger
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2 Comments
 
LVL 48

Accepted Solution

by:
AlexFM earned 500 total points
ID: 8167230
Take a look at this article, it makes some manipulation with second BeginDrag parameter:

http://www.microsoft.com/msj/defaultframe.asp?page=/msj/0898/wicked0898.htm&nav=/msj/0898/newnav.htm
0
 

Author Comment

by:FlorianJaeger
ID: 8167301
Thanks for the example, turns out I forgot:

pImageList->EndDrag();

in the MouseButtonUp ... !

Thanks!!
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