HOWTO: Use Masks to Set/Get Item States in CListCtrl

• The Microsoft Foundation Classes (MFC) included with: - Microsoft Visual C++, 32-bit Editions, versions 4.2, 5.0

SUMMARY

With the CListCtrl class there are no explicit function calls to set or retrieve the states of the list items. This functionality is handled with flags or masks. This article explains how to use these masks to get list items and change their states.

MORE INFORMATION

The CListCtrl class supports the GetItemState, SetItemState and GetNextItem functions. If you use GetNextItem with the appropriate mask, you should be able to locate the desired list item by its order or its state. To change the state you would call GetItemState on the item you have located to obtain the current desired state flag(s), make modifications to the flag(s) and call SetItemState.

GetNextItem

The GetNextItem function takes two parameters. The first indicates which item (0 based) in the list after which you should begin your search. The current item is excluded from the search. To search the entire list, supply a -1 for this parameter.

The second parameter indicates the state that identifies the item for which you are searching. For the CListCtrl, the flags all begin with LVNI_. (see the documentation on CListCtrl::GetNextItem for a complete list).

GetItemState, SetItemState

The GetItemState function will returns a UINT indicating current state flag(s) of the indicated list item. SetItemState accepts a UINT to set the state flag(s) of the indicated list item. Both of these functions take a UINT mask that indicates which of the state flags should be affected.

REFERENCES

Sample Code

The following code demonstrates how to select all items in the CListCtrl that begin with the letter "A" and deselect all others. Note that m_listCtrl is a ClassWizard added control data member declared as CListCtrl.

   void CMyView::OnInitialUpdate()
   {
      CFormView::OnInitialUpdate();

      m_listCtrl.InsertColumn(0, "Western States", LVCFMT_LEFT, 150);

      LV_ITEM lvItem;
      ZeroMemory(&lvItem, sizeof(lvItem));
      lvItem.mask = LVIF_TEXT | LVIF_STATE;

      lvItem.iItem = 0;
      lvItem.state = LVIS_CUT | LVIS_SELECTED;
      lvItem.pszText = "Washington";
      m_listCtrl.InsertItem(&lvItem); // initially selected

      lvItem.iItem = 1;
      lvItem.state = LVIS_CUT | LVIS_SELECTED;
      lvItem.pszText = "Arizona";
      m_listCtrl.InsertItem(&lvItem); // initially selected

      lvItem.iItem = 2;
      lvItem.state = LVIS_CUT;
      lvItem.pszText = "Alaska";
      m_listCtrl.InsertItem(&lvItem);

      lvItem.iItem = 3;
      lvItem.state = LVIS_CUT;
      lvItem.pszText = "California";
      m_listCtrl.InsertItem(&lvItem);

      lvItem.iItem = 4;
      lvItem.state = LVIS_CUT;
      lvItem.pszText = "Nevada";
      m_listCtrl.InsertItem(&lvItem);

      UINT nState;
      CString strText;
      int iItem = -1;

      // as long as GetNextItem found an item...
      while ((iItem = m_listCtrl.GetNextItem(iItem, LVNI_ALL)) > -1 )
      {
         // get item string
         strText = m_listCtrl.GetItemText(iItem, 0);

         // show initial state of flags
         nState = m_listCtrl.GetItemState(iItem, LVIS_SELECTED | LVIS_CUT);
         TRACE("%s state flag is %0x\n", strText, nState);

         // Get only LVIS_SELECTED flag
         // note that LVIS_CUT is not returned in nState
         nState = m_listCtrl.GetItemState(iItem, LVIS_SELECTED);

         // select states beginning with 'A'
         if (strText[0] == 'A' && !nState) {
            TRACE("%s needed to be selected\n", strText);
            m_listCtrl.SetItemState(iItem,
               LVIS_SELECTED,  // nState
               LVIS_SELECTED); // nMask

         // deselect states that don't begin with 'A'
         } else if (strText[0] != 'A' && nState) {
            TRACE("%s needed to be deselected\n", strText);
            m_listCtrl.SetItemState(iItem,
               0,              // nState
               LVIS_SELECTED); // nMask
         }

         // show new flags if modified, note that LVIS_CUT wasn't affected
         nState = m_listCtrl.GetItemState(iItem, LVIS_SELECTED | LVIS_CUT);
         TRACE("%s state flag is now %0x\n", strText, nState);
      }
   }

Keywords          : MfcMisc
Technology        : kbMfc
Version           : WINDOWS NT:4.2,5.0
Platform          : NT WINDOWS