Selecting Items in CTreeCtrl
Ramaswamy Hari -- hari@nextwave.com
Friday, February 02, 1996
Hi,
I have a CTreeCtrl in which I have customized the OnItemExpanded
and OnItemExpanding messages. In OnItemExpanding I add child items
and when that node is collapsed I remove these items rather than keeping
it in the tree. I want to implement a functionality similar to the
synchronize contents in the Microsoft Developer Studio. Basically given
a topic find it in the tree view automatically.
Here is the problem I am facing. I find the handle of a parent item and
when I try to expand it using m_tree.Expand(hItem, TVE_EXPAND) it does not
call my customized OnItemExpanding routine. What am I doing wrong here ?
I have attached the code I use to find the item in the tree view as well
as the OnExpanding and OnExpanded routines. I would really appreciate it
if somebody can point out how to fix this problem.
thanks in advance,
-hari
==========================================================================
HTREEITEM CHTView::Synchronize(void *pInfo) // Recursion limited to 15 levels.
{
static int level = 0;
// Check whether the item is already selected.
if (level == 0) {
HTREEITEM selected = m_tree.GetSelectedItem();
if(selected) {
TV_ITEM selItem;
selItem.mask = TVIF_HANDLE|TVIF_PARAM;
selItem.hItem = selected;
m_tree.GetItem(&selItem);
if(selItem.lParam == (long)pInfo) {
return selected;
}
}
}
level++;
if(level >= 15) {
AfxMessageBox("Too many levels of hierarchy.");
level--;
return NULL;
}
// Keep finding the parent and recursively go down to the root.
void *parent = GetParent(pInfo);
HTREEITEM hItem = NULL;
if(parent) hItem = Synchronize(parent);
if((hItem = FindItem(hItem, pInfo)) != NULL) {
if(level == 1) {
if(!m_tree.SelectItem(hItem)) {
level--;
return NULL;
}
} else {
if(!m_tree.Expand(hItem, TVE_EXPAND)) { // <===== This is where I expect it to call CHTView::OnItemexpandedHvtree();
AfxMessageBox("Unable to expand");
}
}
} else {
level--;
return NULL;
}
level--;
return hItem;
}
HTREEITEM CHTView::FindItem(HTREEITEM hParent, void *pInfo)
{
static TV_ITEM itemCheck;
itemCheck.mask = TVIF_HANDLE|TVIF_PARAM;
BOOL found = FALSE;
HTREEITEM hItem = (hParent) ? hParent : m_tree.GetRootItem();
HTREEITEM hCurrent = m_tree.GetChildItem(hItem);
while (hCurrent && !found) {
itemCheck.hItem = hCurrent;
m_tree.GetItem(&itemCheck);
if(itemCheck.lParam == (long)pInfo) {
found = TRUE;
} else {
hCurrent = m_tree.GetNextItem(hCurrent, TVGN_NEXT);
}
}
return hCurrent;
}
void CHTView::OnItemexpandedHvtree(NMHDR* pNMHDR, LRESULT* pResult)
{
NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;
if(pNMTreeView->action == TVE_COLLAPSE) {
m_tree.Expand(pNMTreeView->itemNew.hItem, TVE_COLLAPSE|TVE_COLLAPSERESET);
}
*pResult = 0;
}
void CHTView::OnItemexpandingHvtree(NMHDR* pNMHDR, LRESULT* pResult)
{
NM_TREEVIEW* pNMTreeView = (NM_TREEVIEW*)pNMHDR;
Populate(pNMTreeView->itemNew.hItem);
UpdateWindow();
*pResult = 0;
}
Ken Freeman -- kfreeman@viewlogic.com
Monday, February 05, 1996
[Mini-digest: 3 responses]
Ramaswamy Hari wrote:
>
> Here is the problem I am facing. I find the handle of a parent item and
> when I try to expand it using m_tree.Expand(hItem, TVE_EXPAND) it does not
> call my customized OnItemExpanding routine. What am I doing wrong here ?
The control does not generate item expanding/expanded messages if you
send it TVE_EXPAND. You'll have to either generate the messages
yourself or just call the handlers directly.
And no, I have no idea why the tree control was written this way.
Ken
-----From: Seth Goldstein
Well hidden, I must say. No mention of it in CTreeCtrl::Expand.
>From the doc on TVM_EXPAND:
"This message does not send the TVN_ITEMEXPANDING and
TVN_ITEMEXPANDED notification messages to the parent window."
You should extract the common piece of code from the message
handler and call it directly from both places.
Hope this helps,
Seth
--
+------------------------------------------------------+
| Seth Goldstein email: seth@mathworks.com |
| The Mathworks, Inc. http://www.mathworks.com |
| info: info@mathworks.com |
|------------------------------------------------------|
| PGP Public Key on server |
| http://www-swiss.ai.mit.edu/~bal/pks-toplev.html |
+------------------------------------------------------+
-----From: Seth Goldstein
Well hidden, I must say. No mention of it in CTreeCtrl::Expand.
>From the doc on TVM_EXPAND:
"This message does not send the TVN_ITEMEXPANDING and
TVN_ITEMEXPANDED notification messages to the parent window."
You should extract the common piece of code from the message
handler and call it directly from both places.
Hope this helps,
Seth
--
+------------------------------------------------------+
| Seth Goldstein email: seth@mathworks.com |
| The Mathworks, Inc. http://www.mathworks.com |
| info: info@mathworks.com |
|------------------------------------------------------|
| PGP Public Key on server |
| http://www-swiss.ai.mit.edu/~bal/pks-toplev.html |
+------------------------------------------------------+
Jim Leavitt -- jimll@halcyon.com
Tuesday, February 06, 1996
> > Here is the problem I am facing. I find the handle of a parent item and
> > when I try to expand it using m_tree.Expand(hItem, TVE_EXPAND) it does not
> > call my customized OnItemExpanding routine. What am I doing wrong here ?
>
> The control does not generate item expanding/expanded messages if you
> send it TVE_EXPAND. You'll have to either generate the messages
> yourself or just call the handlers directly.
Hmmm...
The tree controls in my program do respond to that message... When the
message is sent there are no children present for the item, I then
look then up and add them just as Hari is trying to do...
Hari is also using TVE_COLLAPSE_RESET (sp?). Here's what may be going
on. The collapse reset message is modifing the TVITEM and setting the
number of children to zero.
The control will not expand a node with no children. Should Hari get
the TVITEM structure of a node he's just collapsed - reset and set the
hasChildren (once again, perhaps not the right spelling, i'm on my mac
at home) to 1, then the message will work or at least it does for me.
I don't know about the documentation, but the expand call as Hari has
it works for me. I do set the hasChildren member of TVITEM. I do it to
show the little + button next to each node. I'll send some sample code
if you'd like.
Jim Leavitt.
Ken Freeman -- kfreeman@viewlogic.com
Thursday, February 08, 1996
[Mini-digest: 2 responses]
Jim Leavitt wrote:
>
>
> The control will not expand a node with no children. Should Hari get
> the TVITEM structure of a node he's just collapsed - reset and set the
> hasChildren (once again, perhaps not the right spelling, i'm on my mac
> at home) to 1, then the message will work or at least it does for me.
>
> I don't know about the documentation, but the expand call as Hari has
> it works for me. I do set the hasChildren member of TVITEM. I do it to
> show the little + button next to each node. I'll send some sample code
> if you'd like.
Please do. Are you talking about the cChildren field?
-----From: "Roland Pasternack"
I too am having the original problem described below. The MFC call to
CTreeCtrl::Expand() translates to a call to SendMessage() (see Afxcmn.inl),
sending the TVM_EXPAND message. If you look at the documentation for
TVM_EXPAND, it explicitly states that it does *not* send the TVN_ITEMEXPANDING
and TVN_ITEMEXPANDED notification messages to the parent window.
I also fooled around using the information that Jim provided below, but I
couldn't get anything to work this way either. Jim, it would be very useful
at this point if you would send the sample code that you talked about below to
clarify exactly what you did.
It appears that the only solution is to do what was described below:
> You'll have to either generate the messages yourself or just call the
> handlers directly.
Conceptually, it seems better to try and generate the notification yourself,
and let the OnItemExpanding() code handle it. I tried doing this using
SendNotifyMessage(TVN_ITEMEXPANDING, 0, (LPARAM)pnmTreeView), but I have not
been able to get it to work yet. I am using a CTreeView derived object, and
tried sending the message to both the tree view and the tree control inside of
it. I am kind of stumped at this point, and may try repackaging my
OnItemExpanding() code so that it can be called both via the notification, and
from other places within my own code.
Roland
Jim Leavitt -- jimll@halcyon.com
Saturday, February 10, 1996
Hello All:
Earlier Hari wrote:
> Here is the problem I am facing. I find the handle of a parent item =
and
> when I try to expand it using m_tree.Expand(hItem, TVE_EXPAND) it does =
not
> call my customized OnItemExpanding routine. What am I doing wrong here =
?
Then I replied:
> The control will not expand a node with no children. Should Hari get
> the TVITEM structure of a node he's just collapsed - reset and set the
> hasChildren (once again, perhaps not the right spelling, i'm on my mac
> at home) to 1, then the message will work or at least it does for me.
>>>>>>>I'll send some sample code if you'd like
Which was actually all wet because TVE_EXPAND | TVE_EXPANDRESET does set =
the cChildren member to 1. At least I think it does, the debugger says =
so. I do set cChildren to 1 when I populate the tree, perhaps =
EXPANDRESET is getting the original cChildren member back?
So if I really understand what Hari wants to do... he'd like to navigate =
the tree inside his code and whenever an item needed to expand and add =
more children (database search for example), he'd like his =
OnItemExpanding routine called.
Here's some sample code that does just that. Let's talk about it.=20
First, I used the CTreeCtrlEx and CTreeCursor classes from the DaoView =
sample on the VC4 cd. They take a lot of the work out of using tree =
controls. Those source files are included.=20
Next, I derived my own class ... Ctree that inherited from CTreeCtrlEx. =
I did so because I wanted some other members and attributes for my own =
application. That source is included as well. I've pared it down as much =
as possible so there isn't so much of my junk in it.
Third, I derived some very specific Trees from Ctree. Again, I think it =
makes sense for my application and it works so I'm happy. I've included =
one such tree in this sample, again mightily pared down to make it =
easier to read. Basically I just grabbed some stuff from my application, =
cut out about two thirds of it and jammed it into this sample. The =
coding is rough. (disclaimer :-).
Fourth, the Trees sit on a CTabView, derived from CCtrlView. I had to =
get specific with those too. Theres a base CTabView class here and a =
more specific view (CLeftView, it occupies the left pane in my =
application.) But there all really just windows, I don't believe that =
affects the message passing in MFC or does it ?=20
Fifth, I wondered if you COLLAPSERESET a tree if it really truly freed =
all its memory. I was assured of this by Microsoft Technical Support. =
(Just in case anyone wanted to know... I did.).
The sample puts up a static splitter window with two tab views with =
three tabs each. Each tab has an instance of CDateTree derived as above. =
Look under the View menu - there an Expand Node and a Collapse Node menu =
item, they do what they say. The menu item gets the selected node from =
the Tree, verifies that it can be expanded or collapsed, and then calls =
Expand. The OnItemExpanding routine catches the message and dutifully =
obeys. That's my understanding of Hari's question but I feel like I must =
be missing something here, it was no problem and I hope I'm not off the =
point!
Watch your debug menu and you'll see a trace everytime the code enters =
OnItemExpanding. I didn't have to duplicate any of the OnItemExpanding =
code, it works when you click on the tree or when you choose the menu. =
I've also tested some tree expansion before windows popped to the screen =
but it takes too long for my application.
If anyone improves this code (or even looks at it and has some =
suggestions) please feel free to tell me about it. I hope this sample =
doesn't miss Hari's mark. It appears to do what he wants to do.=20
DEVELOPED AND TESTED ONLY UNDER WINDOWS 95
On another subject:
On Mon, 05 Feb 1996, Stephan.Jou@Cognos.COM (Jou, Stephan) wrote:
>Environment:
> ------------
> MSVC 4.0 (with service pack 1 applied)
> MFC 4.0
> Windows NT 3.51 (not using the new shell)
Thanks.
> I dynamically create a CListCtrl as a child window of a CTabCtrl.=20
> (Both are members of the CView-derived object.) When I close the =
view, I=20
>get
> "Unhandled exception in Test.exe (COMCTL32.DLL): 0xC0000005: =
Access=20
>Violation."
>and the debugger plops me in assembly code within COMCTL32.DLL.
I can either assume I'm making the same error or Stephan found a =
problem. I've placed forms with listViews in my CTabView with no =
problems under 95. I got the same crash today under NT 3.51 service pack =
3. Funny, right at the bottom of the call stack, the application had =
just about exited.
Long winded and tired,
Jim Leavitt=20
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