CListBox::CharToItem

Статья
10/16/2008

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

virtual int CharToItem(
   UINT nKey,
   UINT nIndex 
);

Параметры

nKey
The ANSI code of the character the user typed.
nIndex
The current position of the list-box caret.

Возвращаемое значение

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

Заметки

The WM_CHARTOITEM message is sent by the list box when it receives a WM_CHAR message, but only if the list box meets all of these criteria:

Is an owner-draw list box.
Does not have the LBS_HASSTRINGS 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.

In your override, you must return a value to tell the framework what action you performed. A return value of – 1 or – 2 indicates that you handled all aspects of selecting the item and requires no further action by the list box. Before returning – 1 or – 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 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 a numeric key and up one item 
// on an alphabetic 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::CharToItem(UINT nChar, UINT nIndex)
{
   // On a numeric key, move the caret up one item.
   if (isdigit(nChar) && (nIndex > 0))
   {
      SetCaretIndex(nIndex-1);
   }
   // On an alphabetic key, move the caret down one item.
   else if (isalpha(nChar) && (nIndex < (UINT)GetCount()))
   {
      SetCaretIndex(nIndex+1);
   }

   // Do not perform any default processing.
   return -1;
}