Select and delete from list

Download src.zip - 1.5 KB

Download Keyboard.zip - 29.7 KB

Introduction

This projects demonstrates how one can delete different rows in a list at the same time. It also show how to use key press can initiate a function. I have used pretranslatemessage and accelerator keys to invoke the function required.

Using PreTranslateMessage to handle dialog keystrokes

Very often you hear questions from novice programmers asking how they can trap keystrokes in a dialog based application. Presumably they tried to handle WM_KEYDOWN/WM_KEYUP unsuccessfully. The whole problem is that in a dialog based application the focus is always on one of the child controls and not on the main dialog window. So what do you need to do? You need to override PreTranslateMessage. I'll show you a simple example.

In the application I am using delete button of the keyboard to call OnBnClickedDelete()which will delete the selected items on the list control. The solution is so very easy and straightforward with PreTranslateMessage as I'll demonstrate below.

BOOL CKeyboard1Dlg::PreTranslateMessage(MSG* pMsg) 
{
    if(pMsg->message==WM_KEYDOWN)
    {
        if(pMsg->wParam==(VK_DELETE))
                 OnBnClickedDelete();
    
    }    
 if (m_hAcceleratorTable != NULL)
  if (::TranslateAccelerator(m_hWnd, m_hAcceleratorTable, pMsg))
   return TRUE;

    return CDialog::PreTranslateMessage(pMsg);
}

All I have done is to check whether the message is a WM_KEYDOWN, and if it is so, then I check to see if the wParam is VK_DELETE. If I find it so, OnBnClickedDelete()will be called.

Using Accelerator Keys

To add accelerators you first need to do the following steps

1. Right click on the file name in the resource view and click on add resource.
2. Add a new accelerator.
3. An accelerator window will open. In the first column put the ID of the the function you want to call.
4. Then chose the modifier that you want along with the key.
5. The type VRITKEY is used when ctrl or alt etc is used with a key, if only key is used then used type ASCII.
6. Finally add the code in the PreTranslateMessage function.

if (m_hAcceleratorTable != NULL)
  if (::TranslateAccelerator(m_hWnd, m_hAcceleratorTable, pMsg))
   return TRUE; 

Multiselection in a list

The following code is used to delete the multi selected items.

void CKeyboard1Dlg::OnBnClickedDelete()
{
    
for (int nItem = 0; nItem < m_MainList.GetItemCount(); )
{
  if (m_MainList.GetItemState(nItem, LVIS_SELECTED) == LVIS_SELECTED)
    m_MainList.DeleteItem(nItem);
  else
    ++nItem;
}
} 

Mainlist is the variable of the list control. LVIS_SELECTED is used to get the items which are selected.

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