Error in ListBox->GetDataItemPtr

Klaus Kurzawa -- klausk@saruman.cadpoint.se
Friday, January 05, 1996



Text item: Text_1

     Hi,
     
     Can someone tell me why this procedure always fails. Could the error 
     be somewhere else?
     
     // Getting the listbox
     //
     CListBox* pLB=(CListBox*)GetDlgItem(IDC_LBOX_OBJECTS);
     
     // This is a valid array
     //
     CTypedPtrArray&Object = GetObjectTable(); 
     for (int cI=0; cIAddString("Test string");              // Add a string 
        pLB->SetItemDataPtr(cI, (void*)Object[cI]); // Save the at the row
     
        // This prints the correct addresses for each index 
        //
        TRACE("\ncI:%d pPtr:%ld", cI, pLB->GetItemDataPtr(cI));
     }
     
     // This prints all zero
     TRACE("\ncI:%d pPtr:%ld", 0, pLB->GetItemDataPtr(0));
     
     RESULT:
     cI:1 pPtr:4484520
     cI:2 pPtr:4485044
     cI:3 pPtr:4485732
     cI:0 pPtr:0        <- Error!!
     
     Please help me! This error just began and I don't know when it 
     started.
     
     /Klaus Kurzawa
     klausk@cadpoint.se
     
     

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Joern Dahl-Stamnes -- Jorn.Dahl-Stamnes@fysel.unit.no
Monday, January 08, 1996

>Text item: Text_1
>
>     Hi,
>     
>     Can someone tell me why this procedure always fails. Could the error 
>     be somewhere else?
>     
>     // Getting the listbox
>     //
>     CListBox* pLB=(CListBox*)GetDlgItem(IDC_LBOX_OBJECTS);
>     
>     // This is a valid array
>     //
>     CTypedPtrArray&Object = GetObjectTable(); 
>     for (int cI=0; cI     {
>        pLB->AddString("Test string");              // Add a string 
>        pLB->SetItemDataPtr(cI, (void*)Object[cI]); // Save the at the row

Try this:
	int index = pLB->AddString("Test string");              // Add a string
	pLB->SetItemDataPtr(index, (void*)Object[cI]); // Save the at the row

Hope this help.

>     
>        // This prints the correct addresses for each index 
>        //
>        TRACE("\ncI:%d pPtr:%ld", cI, pLB->GetItemDataPtr(cI));
>     }
>     
>     // This prints all zero
>     TRACE("\ncI:%d pPtr:%ld", 0, pLB->GetItemDataPtr(0));
>     
>     RESULT:
>     cI:1 pPtr:4484520
>     cI:2 pPtr:4485044
>     cI:3 pPtr:4485732
>     cI:0 pPtr:0        <- Error!!
>     
>     Please help me! This error just began and I don't know when it 
>     started.
>     
>     /Klaus Kurzawa
>     klausk@cadpoint.se

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| Joern Yngve Dahl-Stamnes, The University of Trondheim, Norway   |
| e-mail: Jorn.Dahl-Stamnes@fysel.unit.no                         | 
| phone : +73 59 44 12, fax: +73 59 14 41                         |
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Dale Wilson -- dale@dra.com
Tuesday, January 09, 1996


> >     for (int cI=0; cI >     {
> >        pLB->AddString("Test string");              // Add a string
> >        pLB->SetItemDataPtr(cI, (void*)Object[cI]); // Save the at the 
row
> >     /Klaus Kurzawa
> >     klausk@cadpoint.se
>
> Try this:
>         int index = pLB->AddString("Test string");              // Add a
> string
>         pLB->SetItemDataPtr(index, (void*)Object[cI]); // Save the at the 
row
> | Joern Yngve Dahl-Stamnes, The University of Trondheim, Norway   |

Joern didn't explain why his fix works, but once I saw it, it was *obvious*. 
 You probably have the list box sorting your items for you, so the index of 
the item you just added is not cl, but rather the position at which the item 
landed in the sorted order.

Dale Wilson dale@dra.com

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