winapi listview check item c++ - c++

Question

I use minGW32 compiler.
I created a ListView with checkbox something like this:
HWND hListView = CreateWindowExW(0, WC_LISTVIEWW, L"",
WS_VISIBLE | WS_CHILD | WS_TABSTOP | LVS_REPORT | LVS_EDITLABELS,
10,10,500,500, hwnd, (HMENU)ID_LISTVIEW, GetModuleHandle(NULL), NULL);
SendMessage(hListView, WM_SETFONT, (WPARAM) font, TRUE);
ListView_SetExtendedListViewStyle(hListView, LVS_EX_CHECKBOXES | LVS_EX_FULLROWSELECT | LVS_EX_HEADERDRAGDROP | LVS_EX_GRIDLINES/*LVSCW_AUTOSIZE_USEHEADER*/);
lvc.mask = LVCF_TEXT | LVCF_SUBITEM | LVCF_WIDTH | LVCF_FMT;
lvc.fmt = LVCFMT_LEFT;
And I would like to check when any checkbox is checked. for example. If I check any checkbox show me a messagebox:
I use this WM_NOTIFY:
case WM_NOTIFY:
{
switch (LOWORD(wParam))
{
case ID_LISTVIEW:
{
switch (((LPNMHDR) lParam)->code)
{
case LVN_ITEMCHANGED :
MessageBoxW( NULL, (LPCWSTR)lpMsgBuf, L"Error", MB_OK | MB_ICONERROR );
}
break;
}
break;
}
break;
}
break;
But this alwas happened. When I click an empty area of the ListView or when just click any item. But I would like to run the messagebox ONLY when the checkbox is changed.

Answer 1

LPNMLISTVIEW pnmv = (LPNMLISTVIEW) lParam;
if(pnmv->uChanged & LVIF_STATE) // item state has been changed
{
switch(pnmv->uNewState & LVIS_STATEIMAGEMASK)
{
case INDEXTOSTATEIMAGEMASK(2):
// pnmv->iItem was checked
break;
case INDEXTOSTATEIMAGEMASK(1):
//pnmv->iItem was unchecked
break;
}
}