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CListCtrl selection change (2)

Posted on 2000-05-06
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Last Modified: 2013-11-20
One of the most common events to be handled for listboxes is the fact that the item selection has changed. However I did not find any direct way of handling such event. What I am doing is Handling the LVN_ITEMCHANGED msg and using nasty condition like this:

void Foo::OnItemchanged(NMHDR* pNMHDR, LRESULT* pResult)
{
NM_LISTVIEW* pNMListView =(NM_LISTVIEW*)pNMHDR;

if (!(pNMListView->uOldState & LVIS_SELECTED) && 
(pNMListView->uNewState & LVIS_SELECTED)
|| (pNMListView->uOldState & LVIS_SELECTED) && 
!(pNMListView->uNewState & LVIS_SELECTED))
{
//do sth on selection change
}
}
Apart from the ugliness of this solution, the code under the condition is often called twice per one selection change (for item being deselected and for item that gets selected). I would like to have sth. that would work like LBN_SELCHANGE msg. for simple listbox.
Is there any nice solution?

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Question by:ewajoz
2 Comments
 
LVL 49

Accepted Solution

by:
DanRollins earned 300 total points
ID: 2784576
Here's the useful fn I use in a variety of related cases:
-=-=-=-=-=-=-=-=-=-
int GetSelItemIdx( CListCtrl& ctlList )
{
  int  nItmIdx= -1;
  if ( ctlList && ::IsWindow(ctlList.m_hWnd) && ctlList.GetSelectedCount() > 0 ) {
    POSITION pos= ctlList.GetFirstSelectedItemPosition();
    if (pos != NULL) {
        nItmIdx= ctlList.GetNextSelectedItem(pos);
    }
  }
  return( nItmIdx );
}
-=-=-=-=-=-=-=-=-=-

Your handler can call this to get the current selection and (possibly check to see if it is the same as the previous one before taking action).

As to the double notifications:  Just code to check the uNewState:

if ( (pNMListView->uNewState & LVIS_SELECTED) ) {
  /// user just selected a new (previously unselected) item
}
 
Another hint: It simplifies your task to check the Single Selection option in the List Control Properties in the dlg box editor. (I have rarely found the need for multiple selections, and when I need that sort of functionality I use the ListBox control that has checkboxes in it).


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Author Comment

by:ewajoz
ID: 2784604
Thanks, DanRollins
With respect to the first part of your comment: your method requires storing recently selected item or even items, if the list is multiple selection (mine is), which somehow I do not fancy too much.
What refers to the second part: when only checking against the LVIS_SELECTED you lose the situation, when the user deselects an item (by clicking on the selected item, or on the area beyond items) That is why my condition is so huge.
Using checkboxes combined with single selection is certainly a good idea, which I will probably apply.
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