MFC Library and Event handling

MFC Library:

It is a collection of reusable classes that are used for the window program. This library is provided by the dynamic link library (DLL). DLL consists of many executable functions.

The MFC program can be created by two ways –

1.     Using Shared DLL.

2.     Using App and Class wizard.

·        Create MFC program using AppWizard –

                                                                                i.            Start visual studio, click on File menu->New. Select MFC AppWizard(.exe). And give the name of project. And click on ok button.

                                                                              ii.            On new window select single document radio button then click next.

                                                                            iii.            On wizard step 3, select none radio button and click next.

                                                                           iv.            On wizard step 4, uncheck the printing and print preview option and click next button.

                                                                             v.            On wizard step 5, select radio button MFC standard, as a shared DLL.

                                                                           vi.            On wizard step 6, Indicate class name, header file name and implementation name, then click on finish.

                                                                         vii.            Now screen show that AppWizard generate following code.

Event Handling:

MFC program allow the user to handle various events such as key press and mouse click. These events can be sent to the application in the form of message.

Some events in VC++

WM_KEYDOWN

WM_KEYUP

WM_LBUTTONDOWN

WM_RBUTTONDOWN
WM_LBUTTONUP
WM_RBUTTONUP
WM_LBUTTONDBLCLK
WM_RBUTTONDBLCLK
WM_MOUSEMOVE

In order to handle these messages there exist message map which convert these messages to the handler function.

For Ex:

The handler function for the message WM_LBUTTONUP will be.

Void ProjView::OnLButtonUp(UINT nFlag, CPoint point)

{

            //ToDo Add code here

            CView :: OnLButtonUp(nFlag,point);

}

This skeleton code for the message handler function will be get using class wizard. The above code gets generated in ProjView.cpp file. The declaration of this function will be in ProjView.h file

Note: "Proj" is Project name here.

afx_msg void OnLButton(UINT nFlags, CPoint point);

The afx_msg means that this is a prototype declaration and there should some message map for this declaration. This message map is a macro which will be as follows –

BEGIN_MESSAGE_MAP(ProjView, Cview)

            ON_WM_LBUTTONUP() //Entry specifically for OnLButtonUp

            //Other message map entries

END_MESSAGE_MAP()