How to Create a Multiple-Selection List Box
This topic demonstrates how to display and access the contents of a directory in a multiple-selection list box. In a multiple-selection list box, the user can select more than one item at a time.
The C++ code example in this topic enables a user to view a list of files in the current directory, select a group of files from the list, and delete them.
What you need to know
Technologies
Prerequisites
- C/C++
- Windows User Interface Programming
Instructions
The directory listing application must perform the following list box–related tasks:
- Initialize the list box.
- Retrieve the user's selections from the list box.
- Remove the file names from the list box after the selected files have been deleted.
In the following C++ code example, the dialog box procedure initializes the multiple-selection list box (IDC_FILELIST) by using the DlgDirList function to fill the list box with the names of all the files in the current directory.
When the user selects a group of files and chooses the Delete button, the dialog box procedure sends the LB_GETSELCOUNT message, to retrieve the number of files selected, and the LB_GETSELITEMS message, to retrieve an array of selected list box items. After deleting a file, the dialog procedure removes the corresponding item from the list box by sending the LB_DELETESTRING message.
#define BIGBUFF 8192
INT_PTR CALLBACK DlgDelFilesProc(HWND hDlg, UINT message,
UINT wParam, LONG lParam)
{
PTSTR pszCurDir;
PTSTR pszFileToDelete;
int cSelItems;
int cSelItemsInBuffer;
TCHAR achBuffer[MAX_PATH];
int aSelItems[BIGBUFF];
int i;
BOOL fResult;
HWND hListBox;
int iRet;
switch (message) {
case WM_INITDIALOG:
// Initialize the list box by filling it with files from
// the current directory.
pszCurDir = achBuffer;
GetCurrentDirectory(MAX_PATH, pszCurDir);
DlgDirList(hDlg, pszCurDir, IDC_FILELIST, IDS_PATHTOFILL, 0);
SetFocus(GetDlgItem(hDlg, IDC_FILELIST));
return FALSE;
case WM_COMMAND:
switch (LOWORD(wParam))
{
case IDOK:
// When the user presses the DEL (IDOK) button,
// first retrieve the list of selected files.
pszFileToDelete = achBuffer;
hListBox = GetDlgItem(hDlg, IDC_FILELIST);
cSelItems = SendMessage(hListBox,
LB_GETSELCOUNT, 0, 0);
cSelItemsInBuffer = SendMessage(hListBox,
LB_GETSELITEMS, 512, (LPARAM) aSelItems);
if (cSelItems > cSelItemsInBuffer)
{
MessageBox(hDlg, L"Too many items selected.",
NULL, MB_OK);
}
else
{
// Make sure the user really wants to delete the files.
iRet = MessageBox(hDlg,
L"Are you sure you want to delete these files?",
L"Deleting Files", MB_YESNO | MB_ICONEXCLAMATION);
if (iRet == IDNO)
return TRUE;
// Go through the list backward because after deleting
// an item the indices change for every subsequent
// item. By going backward, the indices are never
// invalidated.
for (i = cSelItemsInBuffer - 1; i >= 0; i--)
{
SendMessage(hListBox, LB_GETTEXT,
aSelItems[i],
(LPARAM) pszFileToDelete);
fResult = DeleteFile(pszFileToDelete);
if (!fResult)
{
MessageBox(hDlg, L"Could not delete file.",
NULL, MB_OK);
}
else
{
SendMessage(hListBox, LB_DELETESTRING,
aSelItems[i], 0);
}
}
SendMessage(hListBox, LB_SETCARETINDEX, 0, 0);
}
return TRUE;
case IDCANCEL:
// Destroy the dialog box.
EndDialog(hDlg, TRUE);
return TRUE;
default:
return FALSE;
}
default:
return FALSE;
}
}
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