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Add controls inheritance to your application

Author: Kirk Stowell
Posted: November 16, 2007
Environment: Visual C++ MFC

If you need to add new functionality to standard Command Bar controls (CXTPControlButton, CXTPControlPopup, CXTPControlComboBox, CXTPControlEdit) you must create a new class inherited from one of these and override some virtual methods. This tutorial describes how to create custom Combo Box.

Imagine that you need a combo box with uppercase letters only (When users enter a character it automatically becomes uppercase)

  1. Create a new class inherited from CXTPControlComboBox


    2.  class CControlComboBoxEx: public CXTPControlComboBox

     {

         public:

     };



  2. To create custom edit we must override CreateEditControl method and add a new Edit Control inherited from CXTPControlComboBoxEditCtrl


    3.  class CControlComboBoxEx: public CXTPControlComboBox

     {

     public:

         CXTPControlComboBoxEditCtrl* CreateEditControl()

         {

             return new CControlComboBoxEditEx();

         }

     };

     

     class CControlComboBoxEditEx : public CXTPControlComboBoxEditCtrl

     {

     };



  3. Add OnChar handler to automatically uppercase the characters that the user entered


    4.  class CControlComboBoxEditEx : public CXTPControlComboBoxEditCtrl

     {

     public:

         afx_msg void OnChar(UINT nChar, UINT nRepCnt, UINT nFlags);

     

         DECLARE_MESSAGE_MAP()

     };

     

     

     BEGIN_MESSAGE_MAP(CControlComboBoxEditEx,

                         CXTPControlComboBoxEditCtrl)

         ON_WM_CHAR()

     END_MESSAGE_MAP()

     

     void CControlComboBoxEditEx::OnChar(UINT nChar,

                                         UINT nRepCnt, UINT nFlags)

     {

         CString strChar((TCHAR)nChar), strUpper((TCHAR)nChar);

         strUpper.MakeUpper();

     

         if (strChar != strUpper) ReplaceSel(strUpper, TRUE);

         else CXTPControlComboBoxEditCtrl::OnChar(nChar,

                                                 nRepCnt, nFlags);

     

     }



  4. If your application uses customization you must add methods to restore your combo box after the program reloads


    • Add standard DECLARE and IMPLEMENT macros


      •  class CControlComboBoxEx: public CXTPControlComboBox

       {

           DECLARE_XTP_CONTROL(CControlComboBoxEx)

       public:

           CXTPControlComboBoxEditCtrl* CreateEditControl()

           {

               return new CControlComboBoxEditEx();

           }

       };

       IMPLEMENT_XTP_CONTROL(CControlComboBoxEx, CXTPControlComboBox)



    • If your control has its own variables that need to be stored/restored you must override Copy and Serialize methods


      •  class CControlComboBoxEx: public CXTPControlComboBox

       {

           …

       

       protected:

           void Copy(CXTPControl* pControl,

               BOOL bRecursive = FALSE);

           virtual void Serialize(CArchive& ar);

       

       protected:

           CString m_strMask;

       };

       

       void CControlComboBoxEx::Copy(

               CXTPControl* pControl, BOOL bRecursive)

       {

           ASSERT_KINDOF(CControlComboBoxEx, pControl);

       

           m_strMask = ((CControlComboBoxEx*)pControl)->m_strMask;

       

           CXTPControlComboBox::Copy(pControl, bRecursive);

       }

       void CControlComboBoxEx::Serialize(CArchive& ar)

       {

           CXTPControlComboBox::Serialize(ar);

       

           if (ar.IsStoring())

           {           

               ar << m_strMask;

           }

           else

           {

               ar >> m_strMask;       

           }   

       }



  5. Now you can create your control in the OnCreateControl handler


    6.  BEGIN_MESSAGE_MAP(CMainFrame, CMDIFrameWnd)

         ON_XTP_CREATECONTROL()

     END_MESSAGE_MAP()

     

     int CMainFrame::OnCreateControl(

                     LPCREATECONTROLSTRUCT lpCreateControl)

     {

         if (lpCreateControl->nID == ID_POPUP_COMBO)

         {

             CXTPControlComboBox* pComboFind =

             (CXTPControlComboBox*)CControlComboBoxEx::CreateObject();

             pComboFind->SetDropDownListStyle();       

             pComboFind->SetFlags(xtpFlagManualUpdate);

     

             lpCreateControl->pControl = pComboFind;

             return TRUE;

         }

         return FALSE;

     }