Hi all ! This is my very first CodeProject article, so if anyone gives me a low mark, I would truly like to know why (so that I may improve). Since I've been a faithful CodeProject.com reader for about 3-4 years, I decided to finally submit one of the many things I've had around that hopefully will be useful to someone else.
This article details how one can use my
cTree class that allows one to implement drag and drop easily and to create a background image for their
TreeCtrl rapidly. My picture and the shadowed url in the sample image above are all part of the TreeCtrl's background ! I couldn't capture the real No-arrow, as capturing the screen does not capture the mouse icon so I had to make it in Photoshop (hence the abnormally fat No-Arrow :-)). But the above image is just to give you an idea of what my class can do so download it to see !
This class allows you to also implement Drag & Drop without doing anything, and it only allows dragging to occur between root nodes (you can easily change this if you so desire).
The core of everything is located in
Drag & Drop is implemented with
OnBeginDrag I cast a
NMHDR to a
void cTree::OnBeginDrag(NMHDR* pNMHDR, LRESULT* pResult)
NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;
*pResult = 0;
if (GetParentItem(pNMTreeView->itemNew.hItem) == NULL) return ;
m_hitemDrag = pNMTreeView->itemNew.hItem;
m_hitemDrop = NULL;
m_pDragImage = CreateDragImage(m_hitemDrag);
if( !m_pDragImage )
m_bLDragging = TRUE;
POINT pt = pNMTreeView->ptDrag;
ClientToScreen( &pt );
The first thing I do after casting to a
NM_TREEVIEW struct is test whether or not the actual item is a root node. If so I return, though you can easily comment out this line if you want your root nodes to be draggable.
I then save the item dragged into my member var
m_itemDrag which is a
HTREEITEM. m_itemDrop is NULL as the user has just begun to drag the item.
CreateDragImage() returns a pointer of type CImageList (which is a copy of the image associated with
HTREEITEM)that we store in
Next we need to draw the image at the point where the drag began and set the bool
m_bLDragging to true so that we know that dragging has begun. The following code handles any subsequent mouse moves until the left mouse button is let go:
void cTree::OnMouseMove(UINT nFlags, CPoint point)
POINT pt = point;
if ((hitem = HitTest(point, &flags)) != NULL)
if ((GetParentItem(hitem) != NULL) && (cursor_no != ::GetCursor()))
if ((GetParentItem(hitem) == NULL) && (GetParentItem(m_hitemDrag) != hitem ))
if (cursor_arr != ::GetCursor()) ::SetCursor(cursor_arr);
m_hitemDrop = hitem;
In the beginning of
OnMouseMove() we check the bool
m_bLDragging to see if it has previously been set so we know that the user has started to drag an item. If so, then we get the current mouse position and move the dragged item to that position.
Next we call
HitTest() to see if the current mouse position is over an item. If it is not then
NULL is passed back, otherwise it passes us the
HTREEITEM of the item the mouse is over. We call
DragShowNoLock(FALSE) to prevent the
CImageList from drawing (it actually hides) while we are checking the status of the current item.
Next we check that the item that was returned from
HitTest() is not a child item, and if it is we set the cursor to that of the cursor_no so the user sees the cursor change to that of an action that is not permitted. If the item is over a root node we set the cursor to an arrow and proceed allowing the
CImageList to draw the dragged item.
CMainFrame you can see just how easy it is to create a Treectrl and add and delete groups and children:
if (tree_ctrl) tree_ctrl.DestroyWindow() ;
tree_ctrl.Create( WS_VISIBLE |
WS_TABSTOP | WS_CHILD
CFont listBoxFont ;
DEFAULT_PITCH | FF_SWISS,
tree_imageList.Create(IDB_TREE_IMAGELIST,18,7, RGB(255, 0 ,255));
tree_imageList.Add( &bmp, RGB(255,255,255));
tree_ctrl.AddChild("danclark","Other Contacts") ;
tree_ctrl.AddChild("fugazi","Other Contacts") ;
First I declare a member of cTree called
tree_ctrl within MainFrm.h, and within
CreateTreeCtrl we call
Create and pass
SetFont the font type we want our Treectrl to use. We then create a bitmap that we load the resource associated with imagelist into and Add it to the tree_imageList that is then passed to TreeCtrl object SetImageList().
Also, I put the function
SetDefaultCursor within the
cTree's constructor so that it automatically loads the No Cursor and the arrow on creation.
I also decided not to cover the functions that do the drawing of the background of the TreeCtrl as this whole article would be to long for most to read.
Other Useful Functions
AddGroup(CString groupname) - Adds a group to the TreeCtrl
DeleteGroup(CString groupname) - Deletes a group
AddChild(CString childname,CString groupname) - Adds a buddy to the given group
DeleteChild(CString childname,CString groupname) - Deletes a buddy in the given group
GetChildCountInGroup(CString groupname) - Returns number of children in a group
SetBkImage(UINT) - Sets the background image of the TreeCtrl given the resource ID
SetBkImage(LPCTSTR) - Sets the background image of the TreeCtrl given the string location