Lesson 4: MFC Basics
Are you ready to start programming? No you are not. You don’t want me
to teach you a stupid ‘hello world’ application, do you? If you want to
make the most of Visual C++ you have to use Microsoft Foundation Classes
(MFC). These classes are great because they wrap all of those handles we
talked about in the first lesson with easy to use classes. The most important
to you right now is the class CWnd. This wraps the functions which
needed a window handle (HWND). Remember that PostMessage
function I mentioned?
PostMessage(your_HWND, WM_PAINT, 0,0);
Well now we can take our windows class and call it’s member function.
MyCWnd.PostMessage(WM_PAINT, 0, 0);
This does the same thing, but now we don’t have to keep track of the
window handles. But don’t be fooled, they are still there. We can still
use them too. They are now just member variables of the class. The handle
to the window a CWnd is associated with in the member variable
m_hWnd. We can call the old post message this way:
::PostMessage(MyCWnd.m_hWnd, WM_PAINT, 0,0);
Those colons (::) are used to tell MFC that we are calling
the old fashioned versions of the function. You can get away without using
them most of the time, but I put them here so you won’t be too confused
when you see them in microsoft’s code.
The CWnd class is the base for several other classes. Like
CButton and CDialog which I hope the names make self
explanatory. From CButton you can access the windows handle
also. (You’d be surprised how many things are windows.. Scroll bars, edit
boxes, tree views, the desktop…) Got all that? Great!
The next most important class, though you won’t explicitly use it much,
is CWinApp. This class is the backbone of all of your future MFC
applications. This is the class that does the main dirty work under the
hood. Your program will have a CWinApp class, which when created,
starts the program execution. The main function called when the CWinApp
is constructed is InitInstance(). In this
function windows are created and the application is set up. Think of
the InitInstance() function in CWinApp as the main()
section in a C program.
Let’s move on to one last very useful MFC class that you will surely
use: CString. This is one of microsoft’s support classes. It is
used to make string manipulation easier. Since CString overrides
many of the common operators, like = and +, you can do things like this:
CString strMyString; strMyString="May the Force be with you"; strMyString+=" young Jedi." printf("%s", strMyString); //output will be "May the Force be with you young Jedi.";