MFC Quick Start Guide (Part 4): Slider Bar Control

1. Open the Toolbox tab, select Slider Control and drag it to your dialog
   
   
   
   (Fig. 4.1: Slider Control)
2. Do it three times
   
   
   
   (Fig. 4.2: Three Sliders)
3. Rename the IDs of them to be IDC_RED_SLIDER, IDC_GREEN_SLIDER and IDC_BLUE_SLIDER
4. Right click on the edit box first slider bar and choose Add variable
   
   
   
   (Fig. 4.3: Add variable)
5. Input the data according to the following setting:
1. Access: private
2. Check the box “control variable”
3. Category: value
4. Variable Type: CString
5. Variable name: m_RedSliderEcho
   
   
   
   (Fig. 4.4: Setting)
6. Repeat step 5 similarly for the other edit boxes
7. Make sure the Orientation field in the Property panel is horizontal
   
   
   
   (Fig. 4.5: Horizontal)
   
8. Right click on the first slider ctrl and choose Add variable
9. Input the data according to the following setting:
1. Access: private
2. Check the box “control variable”
3. Category: control
4. Variable Type: CSliderCtrl
5. Variable name: m_RedSliderCtrl
   
   
   
   (Fig. 4.6: Setting)
10. Repeat step 9 similarly for the other 2 slider bars

Adding Event Handler

1. Find the line “BEGIN_MESSAGE_MAP(CMFC101Dlg, CDialogEx)” in MFC101Dlg.cpp
   
2. Add this following line of code:
   
   

   ON_WM_HSCROLL()
   

   
   
   
   (Fig. 4.7: Message Map)
3. Add the event handler function by
1. Add the member function inside MFC101Dlg.h
   
   

   afx_msg void OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar);
   

   
   
   
   (Fig. 4.8: Header)
   
   
2. Back to MDC101Dlg.cpp, add the member function
   
   

   void CMFC101Dlg::OnHScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
   {
       // TODO: Add your message handler code here and/or call default
       if ((pScrollBar == (CScrollBar *)&m_RedSliderCtrl) ||
           (pScrollBar == (CScrollBar *)&m_GreenSliderCtrl) ||
           (pScrollBar == (CScrollBar *)&m_BlueSliderCtrl))
       {
           int nIndex;
           nIndex = m_RedSliderCtrl.GetPos();
           m_RedSliderEcho.Format(_T("%d"), nIndex);
           //m_sExposureValue.Format(_T("%d"), nIndex);
   
           nIndex = m_GreenSliderCtrl.GetPos();
           m_GreenSliderEcho.Format(_T("%d"), nIndex);
   
           nIndex = m_BlueSliderCtrl.GetPos();
           m_BlueSliderEcho.Format(_T("%d"), nIndex);
   
           UpdateData(FALSE);
       }
       else
       {
           CDialog::OnHScroll(nSBCode, nPos, pScrollBar);
       }
   }
   

3. Inside the OnInitDialog() function, add the following:
   
   

   m_RedSliderCtrl.SetRange(0, 255, TRUE);
   m_RedSliderCtrl.SetPos(0);
   
   m_RedSliderEcho.Format(_T("%d"), 0);
   
   m_GreenSliderCtrl.SetRange(0, 255, TRUE);
   m_GreenSliderCtrl.SetPos(0);
   
   m_GreenSliderEcho.Format(_T("%d"), 0);
   
   m_BlueSliderCtrl.SetRange(0, 255, TRUE);
   m_BlueSliderCtrl.SetPos(0);
   
   m_BlueSliderEcho.Format(_T("%d"), 0);
   
   

   
   
   
   
   (Fig. 4.9: OnInitDialog())

Build & Run

1. Press Ctrl+shift+B to build the solution 
2. Press Ctrl+F5 to run (without debugging).
3. Try adjusting the positions of the slider bars, the value will show on the edit boxes