How To Trap Arrow Keys in an Edit Control of a Dialog Box

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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:

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

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().

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.

APPLIES TO

Microsoft Foundation Class Library 4.2, when used with:

Microsoft Visual C++ 1.0 Professional Edition
Microsoft Visual C++ 1.5 Professional Edition
Microsoft Visual C++ 1.51
Microsoft Visual C++ 1.52 Professional Edition
Microsoft Visual C++ 1.0 Professional Edition
Microsoft Visual C++ 2.0 Professional Edition
Microsoft Visual C++ 2.1
Microsoft Visual C++ 4.0 Standard Edition

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Retired KB Content Disclaimer

This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.

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