CListBox::VKeyToItem

Статья
10/16/2008

Called by the framework when the list box's parent window receives a WM_VKEYTOITEM message from the list box.

virtual int VKeyToItem(
   UINT nKey,
   UINT nIndex 
);

Параметры

nKey
The virtual key code of the key the user pressed. For a list of of standard virtual key codes, see Winuser.h
nIndex
The current position of the list-box caret.

Возвращаемое значение

Returns – 2 for no further action, – 1 for default action, or a nonnegative number to specify an index of a list box item on which to perform the default action for the keystroke.

Заметки

The WM_VKEYTOITEM message is sent by the list box when it receives a WM_KEYDOWN message, but only if the list box meets both of the following:

Has the LBS_WANTKEYBOARDINPUT style set.
Has at least one item.

You should never call this function yourself. Override this function to provide your own custom handling of keyboard messages.

You must return a value to tell the framework what action your override performed. A return value of – 2 indicates that the application handled all aspects of selecting the item and requires no further action by the list box. Before returning – 2, you could set the selection or move the caret or both. To set the selection, use SetCurSel or SetSel. To move the caret, use SetCaretIndex.

A return value of – 1 indicates that the list box should perform the default action in response to the keystroke.The default implementation returns – 1.

A return value of 0 or greater specifies the index of an item in the list box and indicates that the list box should perform the default action for the keystroke on the given item.

Пример

// CMyODListBox is my owner-drawn list box derived from CListBox. This 
// example moves the caret down one item on the down key and up one item 
// on the up key. The list box control was created with the following 
// code:
//   m_myODListBox.Create(
//      WS_CHILD|WS_VISIBLE|WS_BORDER|WS_HSCROLL|WS_VSCROLL|
//      LBS_SORT|LBS_MULTIPLESEL|LBS_OWNERDRAWVARIABLE|LBS_WANTKEYBOARDINPUT,
//      CRect(10,250,200,450), pParentWnd, IDC_MYODLISTBOX);
//
int CMyODListBox::VKeyToItem(UINT nKey, UINT nIndex)
{
   // On key up, move the caret up one item.
   if ((nKey == VK_UP) && (nIndex > 0))
   {
      SetCaretIndex(nIndex-1);
   }
   // On key down, move the caret down one item.
   else if ((nKey == VK_DOWN) && (nIndex < (UINT)GetCount()))
   {
      SetCaretIndex(nIndex+1);
   }

   // Do not perform any default processing.
   return -2;
}