C / C++ / MFC

Want to extract all the datas from a list box

16-Mar-11 3:37

I don't think the use of CRichEditCtrl would have any bearing on it, but you would need to give more detail about the application and why the programmer believes it is not possible.

[edit]According to the MSDN documentation[^] you can set options in the Findtext() function to search forwards or backwards.[/edit]

I must get a clever new signature for 2011.

leorex16-Mar-11 0:55

16-Mar-11 0:55

Hi. I want to be able to extract all the array associated in a listbox-items, but i am failing to find a thing to put in my for loop. the LB_GETCURSEL doesnt seem to be the correct one here... can someone point me the message I should be using?

HWND handle_List = GetDlgItem(hwnd, IDC_LIST_COMPARE);
            count = SendMessage(handle_List, LB_GETCOUNT, 0, 0);
            for (i =0; i<count; i++)
            {
                //part where I am failing
                int index = SendMessage(handle_List, LB_GETCURSEL, 0, 0);
                int data = SendMessage(handle_List, LB_GETITEMDATA, (WPARAM)index, 0);
                MessageBox (hwnd, (char *)data, "The stored data is", MB_OK);
               //the returned string is always "?".
            }
            break;

this is the link for MSDN listbox thing. http://msdn.microsoft.com/en-us/library/bb775146%28v=vs.85%29.aspx[^]

can someone please point me which message i should be using? thank you very much.
btw i am sure the information/array is associated to the object in the listbox

Hans Dietrich16-Mar-11 1:47

Hans Dietrich

16-Mar-11 1:47

for (i =0; i<count; i++)
{
    int data = SendMessage(handle_List, LB_GETITEMDATA, (WPARAM)i, 0);
    MessageBox (hwnd, (char *)data, "The stored data is", MB_OK);
}

Best wishes,
Hans

[Hans Dietrich Software]

Richard MacCutchan16-Mar-11 1:54

16-Mar-11 1:54

You are using the wrong index value and the wrong message(s) see here[^]. Try the following

char textBuf[64];
for (i =0; i<count; i++)
{
    SendMessage(handle_List, LB_GETTEXT , (WPARAM)i, (LPARAM)textBuf);
    MessageBox (hwnd, textBuf, "The stored data is", MB_OK);
}

[edit]Also, you cannot cast an int to a char* and expect it to display a sensible value.[/edit]

I must get a clever new signature for 2011.

Albert Holguin16-Mar-11 9:38

Albert Holguin

16-Mar-11 9:38

what is a char*? ...its an integer pointer to a string, so it really depends on the other code whether it displays sensible data...

Richard MacCutchan16-Mar-11 12:45

16-Mar-11 12:45

If you read my comment: I said that you cannot cast an int, which is a pure binary number, to a char*, which is a pointer to an array of characters, and expect to get sensible output.

[edit]Hence the OP's comment:

//the returned string is always "?".

[/edit]

I must get a clever new signature for 2011.

Albert Holguin16-Mar-11 13:40

Albert Holguin

16-Mar-11 13:40

that's not true... a char* is an integer... if the int holds the location of the initial character of a string (and the array is null terminated) it can be cast that way.

Richard MacCutchan16-Mar-11 13:49

16-Mar-11 13:49

Is your real name SAKryukov?

I must get a clever new signature for 2011.

Albert Holguin16-Mar-11 14:33

Albert Holguin

16-Mar-11 14:33

...i don't mean it in a mean way, more of a matter of fact sort of way... Big Grin | :-D

leorex16-Mar-11 22:47

16-Mar-11 22:47

Sorry LB_GETTEXT is not what I want. I want the data/string associated with the item. GETTEXT shows me the text for the string that is already displaying in the listbox.

Richard MacCutchan16-Mar-11 22:58

16-Mar-11 22:58

OK just replace the LB_GETTEXT like this:

int data = SendMessage(handle_List, LB_GETITEMDATA, (WPARAM)i, 0);

However you do not say what data you are expecting to get returned from the ListBox. In your original sample you cast the returned value to a char* and then complain you always get "?" printed out, so I am assuming it is not a pointer to a character array. What value do you store in the itemdata when you create the ListBox?

I must get a clever new signature for 2011.

leorex16-Mar-11 23:08

16-Mar-11 23:08

i stored a TCHAR File_name in the listbox. here is the code for how i stored it.

int index = SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_ADDSTRING, 0, (LPARAM)str);

    SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_SETITEMDATA, (WPARAM)index, (LPARAM)File_name);

here is the check I have after I add the string in just to make sure.

HWND hList = GetDlgItem(hwnd, IDC_LIST_COMPARE);

int data = SendMessage(hList, LB_GETITEMDATA, (WPARAM)index, 0);

MessageBox (hwnd, (char *)data, "The stored data for the newly selected item is...", MB_OK);

here the message box displays the string fine. I am pretty much using the exact same code as u have suggested, but i just cannot get it to work in the for loop for some stupid reason -_-;;

Richard MacCutchan17-Mar-11 1:25

17-Mar-11 1:25

A couple of suggestions:
In your data retrieval loop your code might be a bit clearer if you write it as:

char* string = (char*)SendMessage(hList, LB_GETITEMDATA, (WPARAM)i, 0);

Also check that the returned pointer string still points to a valid address. When you add these data items to your list box, if they are pointers to local memory you need to ensure that they are not destroyed. Your code above does not make it clear exactly how they are created, and whether they are permanent.

I must get a clever new signature for 2011.

leorex17-Mar-11 22:52

17-Mar-11 22:52

LOL still doesnt work. this problem is driving me insane... I need to link the filename with the item in the listbox >.<. why does it work on every single example i see on the web! Confused | :confused:

here is the full code. Please tell me if I made any mistake

case WM_COMMAND:
{
    switch(LOWORD(wParam))
    {
    case ID_CMP_LOADFILE:
    {
        OPENFILENAME ofn;
        TCHAR File_name[MAX_PATH];

            //the whole loadfile business here.
            int index = SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_ADDSTRING, 0, (LPARAM)str);
            sprintf(File_name, "1");//implanted this line just to make sure things goes in. I AM SURE ITS NT AN EMPTY STRING!


            SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_SETITEMDATA, (WPARAM)index, (LPARAM)File_name);

            HWND hList = GetDlgItem(hwnd, IDC_LIST_COMPARE);

            int data = SendMessage(hList, LB_GETITEMDATA, (WPARAM)index, 0);

            MessageBox (hwnd, (char *)data, "The stored data for the newly selected item is...", MB_OK);//works perfectly here.....

            fclose(file_opened);
        }
        break;
    }
    case ID_CMP_COMPARE:
    {
        int count;
        int i;
        HWND handle_list = GetDlgItem(hwnd, IDC_LIST_COMPARE);
        count = SendMessage(handle_list, LB_GETCOUNT, 0, 0);
        for (i =0; i<count; i++)
        {
            TCHAR* data = SendMessage(handle_list, LB_GETITEMDATA, (WPARAM)i, 0);
            MessageBox (hwnd, data, "The stored data for the newly selected item is...", MB_OK);//still nothing  :((
        }
        break;
    }

thank you all soo much.. i really need to crack this..

Richard MacCutchan18-Mar-11 0:41

18-Mar-11 0:41

As I said before, you need to be sure that your data fields are pointing at static memory blocks. You have the following line(s) in your code:

TCHAR File_name[MAX_PATH];

//the whole loadfile business here.
int index = SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_ADDSTRING, 0, (LPARAM)str);
sprintf(File_name, "1");//implanted this line just to make sure things goes in. I AM SURE ITS NT AN EMPTY STRING!

SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_SETITEMDATA, (WPARAM)index, (LPARAM)File_name);

However, as soon as you leave this function the variable File_name will be destroyed (because it is on the stack) and your pointer is no longer valid.

You need to do something like:

PTSTR pFile_name;

//the whole loadfile business here.
int index = SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_ADDSTRING, 0, (LPARAM)str);
// get the length of the filename
pFile_name = new TCHAR[the length of the filename + 1];
// copy the filename into the string you just allocated to pFile_name

SendDlgItemMessage(hwnd, IDC_LIST_COMPARE, LB_SETITEMDATA, (WPARAM)index, (LPARAM)pFile_name);

now when you leave this function your filename memory buffer will not be destroyed. You should also remember to delete[] all these memory blocks when you destroy your listbox.

I must get a clever new signature for 2011.

leorex18-Mar-11 15:50

18-Mar-11 15:50

thank you soo much! I actually got it working with a different slightway, because this way everytime I load the filename it gets re-written, so I have to point the pFile_name to a 2D array. And I dnt know whats new, I just used malloc(), but i think it should be the same.
But yeah thank you soo much!

leorex16-Mar-11 23:01