HOWTO: Trap Arrow Keys in an Edit Control of a Dialog Box

• The Microsoft Foundation Classes (MFC), used with:
  • Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5, 1.51, 1.52
  • Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0

SUMMARY

This article describes how to trap arrow keys in an edit control of a dialog box with the Microsoft Foundation Classes (MFC) versions 2.0 and above. Although the example in this article uses an edit control, a similar mechanism applies to other controls as well.

MORE INFORMATION

To trap the arrow keys in an edit control of a dialog box, the following steps may be taken:

1. Create a dialog box class derived from CDialog. For example, you can create a dialog box class called CMyDlg:public CDialog with Class Wizard.



2. Create your own edit class and trap WM_GETDLGCODE and WM_KEYDOWN. The code will resemble the following:

   
         class CMyEdit : public CEdit
         {
         // Construction
         public:
              CMyEdit();
   
         public:
              virtual ~CMyEdit();
         protected:
              afx_msg UINT OnGetDlgCode();
              afx_msg void OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags);
              DECLARE_MESSAGE_MAP()
         };
   
         CMyEdit::CMyEdit()
         {
         }
   
         CMyEdit::~CMyEdit()
         {
         }
   
         BEGIN_MESSAGE_MAP(CMyEdit, CEdit)
              ON_WM_GETDLGCODE()
              ON_WM_KEYDOWN()
         END_MESSAGE_MAP()
   
         UINT CMyEdit::OnGetDlgCode()
         {
   
              return DLGC_WANTARROWS|DLGC_WANTALLKEYS|DLGC_WANTCHARS;
         }
   
         void CMyEdit::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
        {
              //Check if the key pressed was a DOWN ARROW key
              if (nChar == VK_DOWN)
                   AfxMessageBox("It is a down arrow key!");
              if (nChar == VK_RIGHT)
                   AfxMessageBox("It is a right arrow key!");
              if (nChar == VK_LEFT)
                   AfxMessageBox("It is a left arrow key!");
              if (nChar == VK_UP)
                   AfxMessageBox("It is a up arrow key!");
              CEdit::OnKeyDown(nChar, nRepCnt, nFlags);
         } 

   NOTE: if Class Wizard is used to add a CMyEdit class, you must derive the class from CWnd first and then manually change any references of CWnd to CEdit in the code. It is important to trap WM_GEDLGCODE in your own edit class and specify DLGC_WANTARROWS in OnGetDlgCode().



3. Create a member variable that maps to your own edit class in the dialog box class and override CWnd::DoDataExchange(). Your code should resemble the following:

   
         class CMyDlg : public CDialog
         {
         public:
              CMyEdit m_edit;
         protected:
              virtual void DoDataExchange(CDataExchange* pDX); //DDX/DDV
   
              DECLARE_MESSAGE_MAP()
         };
         void CMyDlg::DoDataExchange(CDataExchange* pDX)
         {
              CDialog::DoDataExchange(pDX);
              DDX_Control(pDX, IDC_EDIT1, m_edit);
         } 

   NOTE: This can be done easily by Class Wizard. For example, you can add a member variable m_edit and map it to CEdit and then manually change CEdit references in MyEdit.CPP and MyEdit.H files to CMyEdit.

Additional query words: kbinf 1.00 1.50 1.51 1.52 2.00 2.10 2.50 2.51 3.00 3.10 4.00

Keywords : kbCtrl kbMFC KbUIDesign kbVC kbGrpMFCATL
Version : winnt:1.0,2.0,2.1,4.0
Platform : winnt
Issue type : kbhowto