MFC CListbox GetItemData failed - c++

Question

I used DrawItem() to redraw my CListbox. For some reasons, I want to use custom compare to sort my list item with my own rules, and I use LBS_SORT and no LBS_HASSTRING properties. After using SetItemData() in OnInitDialog(), I get these data in DrawItem(), but it didn't work. Code is like below:
init code :
void OnInitDialog(...)
{
.........
m_List.SetListHeight (40);
for (int i = 0 ; i < 20 ; i ++) {
m_List.AddString ((const char *) i);
m_List.SetItemData (i,(100 + i));
}
....
}
compare code :
int CompareItem(LPCOMPAREITEMSTRUCT lpCompareItemStruct)
{
ASSERT(lpCompareItemStruct->CtlType == ODT_LISTBOX);
int a = lpCompareItemStruct->itemData1;
int b = lpCompareItemStruct->itemData2;
return (a - b);
}
redraw code :
DrawItem (lpDIS)
{
..................
CString str;
int i = (int) GetItemData (lpDIS->itemID); // the i is not what I expect.
str.Format ("%d", (int) i);
dc.DrawText (str,CRect (&lpDIS->rcItem), DT_CENTER | DT_VCENTER | DT_SINGLELINE);
...................
}
when I use
***index = m_List.addstring ((const char *) i) ;
m_List.setitemdata (index,(100 + i));***
it works ,but if I use a struct to addstring ,the index is not right ,code is like this below :
struct test {
int a,b,c,d;
};
init_code :
test *ptest = new test[20]; /* just a test ,we don't delete memory till application ends */
for (int i = 0 ; i < 20 ; i ++) {
ptest [i].a = i;
int index = m_List.AddString ((const char *) (ptest + i));
m_List.SetItemDataPtr (index,(void *) (100 + i));
}
compare code :
int ListEx::CompareItem(LPCOMPAREITEMSTRUCT lpCompareItemStruct)
{
// TODO: Add your code to determine the sorting order of the specified items
// return -1 = item 1 sorts before item 2
// return 0 = item 1 and item 2 sort the same
// return 1 = item 1 sorts after item 2
// ASSERT(lpCompareItemStruct->CtlType == ODT_LISTBOX);
test *pa,*pb;
pa = (test *) lpCompareItemStruct->itemData1; // crashed here
pb = (test *) lpCompareItemStruct->itemData2;
// ASSERT (pa);
// ASSERT (pb);
return (pa->a - pb->a);
}
draw_item code :
CString str;
test *ptest = (test *) (lpDIS->itemData);
str.Format ("%d", (int) ptest->a);
dc.DrawText (str,CRect (&lpDIS->rcItem), DT_CENTER | DT_VCENTER | DT_SINGLELINE);
Is addstring can only use strings ???
if the item is a struct data ,how could I set these struct data to the listbox item ???

Answer 1

In OnInitDialog you should do this:
for (int i = 0 ; i < 20 ; i ++) {
int index = m_List.AddString ((const char *) i);
m_List.SetItemData (index, 100 + i);
}
AddString returns the index where the item has been inserted (which can be anywhere if the list is sorted). m_List.SetItemData (index ,(100 + i)) sets the data for the item you just have inserted.

Answer 2

we can set structure data to list box.
struct _empInfo {
CString strName;
..............
} empInfo = {L"XYZ",...};
m_list.AddString(empinfo.strName);
I tried above code in my app..