Re: Detect changes in ClistCtrl control with checkbox

From:

=?Utf-8?B?YXNvbmkxMg==?= <asoni12@discussions.microsoft.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 13 Jan 2009 23:54:00 -0800

Message-ID:

<E773399F-92A3-4BDE-8F25-E248EAEE05E1@microsoft.com>

Thanks Ian. I did it this way and it works fine for me-
I just wanted to confirm, since I am using constant 0x2000 and 0x1000 here,
can I be sure that these checks will not be bricked in some other environment
like other version of windows OS or Visual Studio?

                int oldState = -1;
        int newState = -1;
        int changedState= -1;

        int ns1 = pNMLV->uOldState & LVIS_STATEIMAGEMASK;
        int ns2 = pNMLV->uNewState & LVIS_STATEIMAGEMASK;

        if ((ns1 & 0x2000) != 0)// find the previous state
        { //Checkbox set
            oldState = 1;
        }
        else if ((ns1 & 0x1000) != 0)
        {
            //Checkbox unset
            oldState = 0;
        }

        if (-1 != oldState)// If got the previous state then find the new state
        {
            if ((ns2 & 0x2000) != 0)
            { //Checkbox set
                newState = 1;
            }
            else if ((ns2 & 0x1000) != 0 )
            {
                //Checkbox unset
                newState = 0;
            }
            if ( (-1 != newState) && (oldState != newState))
            {
                changedState = newState - oldState;
                if (1 == changedState)
                {
                    AfxMessageBox(_T("Item has been checked"));
                }
                else if (-1 == changedState)
                {
                    AfxMessageBox(_T("Item has been unchecked"));
                }
            }
        }

"Ian Semmel" wrote:

In the LVN_ITEMCHANGED handler you can put

int ns = pNMListView ->uNewState & LVIS_STATEIMAGEMASK;

if ( ( ns & 0x2000 ) != 0 )
   // Checkbox set
else if ( ( ns & 0x1000 ) != 0 )
   // Checkbox unset
else
   // Something else happened

asoni12 wrote:

"Ajay Kalra" wrote:

On Jan 13, 11:31 am, asoni12 <ason...@discussions.microsoft.com>
wrote:

I am using a CListCtrl with LVS_EX_CHECKBOXES extended style. How can I
detect that a previously checked item has been unchecked or a previously
unchecked item has been checked. I know that LVN_ITEMCHANGED event is
triggered whenever its state gets changed but how to find if the item has
been checked / unchecked and its previously state.
Any help is appreciated.

Take a look at ListView_GetCheckState: http://msdn.microsoft.com/en-us/library/bb761250(VS.85).aspx
and LVN_ITEMCHANGING: http://msdn.microsoft.com/en-us/library/bb774847(VS.85).aspx

--
Ajay

Hi Ajay,
Thanks for the quick reply.
We get a pointer to an NMLISTVIEW structure in case of both both
LVN_ITEMCHANGING and LVN_ITEMCHANGED event handlers but with this structure
how can we make sure whether items???s checked/unchecked state has been
toggled or something else has changed?
I mean is there any bit in this structure member which is set/unset when the
state gets toggled?