11 introduction to mfc

8/9/2019 11 Introduction to MFC

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Introduction to Microsoft

Foundation Classes



GUID, FPGDST 2004-2005, C-DAC

Background on Object Oriented

Programming

Abstraction

Encapsulation Inheritance

Polymorphism

Modularity




Design Goals of MFC

Deliver a real-world application

± Using C++ and Object Oriented techniques

Deliver an small and fast application framework

± To simplify Windows development

± Allow developers to leverage their existing knowledge

of Windows

± To build large-scale applications that utilize the latest

Windows enhancements, such as OLE and ODBC




Delivering a real-world application

No new programming concepts

± Extends the object-oriented programming model that

was already used by Windows

± Expresses their concepts in standard C++ idioms

Subset of C++ is defined in MFC

± However, no restrictions were placed on code that a

programmer could write

± you can use any feature of C++ you want to




Simplifying the Windows API..

API functions are grouped into logical units. ± All functions related to device context appear in one

class and all functions related to a generic window

appear in one«

Safely hides away the messy details of Windows programming

± such as registering windows classes, window anddialog procedures, and message routing




..S

implifying the Windows API Strong typing and data-encapsulation features of

C++ is used ± To make development mechanically easier

± e.g. Every windows message uses two parameters,WPARAM and LPARAM. However the actual valuesstored in the message maybe any number of things:

pointers, POINT structures, windows handles, etc.

± To retrieve the parameters, the C/SDK programmer

needs to decode the parameters into proper type of values




Using the knowledge you already

have

The class hierarchy and naming conventions on

the underlying API naming conventions

± To minimize the relearning curve for experienced

developers

So converting a standard program written using

SDK to MFC is fairly simple

± Even conversion might not be required




A Firm Foundation The Windows API keeps getting bigger and bigger

± As it continues to collect new material

± Microsoft keeps adding new APIs to Windowsincluding OLE and ODBC

Initial framework does not support every newWindows API

± Was designed so that it could be readily extended.Every new API introduces a new learning curve

± MFC eases things by encapsulating the details of anAPI in a set of classes




Application Framework.. Collection of classes which work in a well defined

manner

Defines fixed steps to create an application

Developer does not have much control

Provides hooks for plugging in developer code




..Application Framework




A Tour of MFC General-Purpose classes

± CObject, CException

Windows API classes

± CCmdTarget, CWinThread, CWinApp

Application framework classes

± CDocument, CView

High Level abstractions

± ScrollView, Splitter




Important Classes CWinApp

CWnd

CFrameWnd

CView

CDocument




CWnd Represents a window

Used for display purposes

Also receives events




CFrameWnd Derived from CWnd

Contains menus, toolbars, status bars and

view window

Constitutes main window of application




CView Represents view window

Used in Document/View

Created as a child of CFrameWnd

Used to display contents of document

Receives events




CD

ocument Represents document object

Used in Document/View

Created as an independent object

Tightly bound to view object




Application WithoutD

oc/View Minimum application

Event handling

Window painting

Menus

Dialog boxes




Basic Windows

Support

Windows sits between the hardware and the

applications it is hosting

± Whenever anything happens that is of interest to one of the applications, Windows informs the application

A substantial amount of code is required by a

windows application to receive and process events




The tasks to be accomplished The Windows application needs to set up a message

handler and plug it into Windows (via RegisterClass()API)

± so that Windows knows where to go and get messageshandled for a specific application

Windows needs to keep track of specific instances of anapplication

The application asks Windows for the next event in themessage queue, dispatches the message to theappropriate message handler, and then gets the next one

This activity continues till the application ends




Requirements of a Windows

Program.. The program must contain a WinMain() function.

± Just as every C program requires a main() function, every

± WinMain() acts as the entry point for the program. It is through the WinMain() function that the application receives

from Windows the information necessary for it to run

The application must register at least one windowclass to serve as the main window ± It is the window¶s job to present the user interface on the

screen




..Requirements of a Windows

Program Most applications require some initialization and setup

This initialization usually takes two forms

± application-specific ± instance-specific initialization

± The program needs to provide any necessary initialization

steps

The application must provide a message handler ± The function of the window procedure is to handle messages

± At the very least, the window procedure must handle the

WM_DESTROY message




Sample - Minimum Application




A minimum Application

#include <afxwin.h>

//Define an application class derived from CWinApp

class CGenericApp : public CWinApp {

public:

virtual BOOL InitInstance();};

class CGenericWindow : public CFrameWnd {

public:

CGenericWindow() {

Create(NULL, ³Generic´);}

afx_msg void OnLButtonDown(UINT nFlags, CPoint point);

DECLARE_MESSAGE_MAP()

};




A minimum Application

BEGIN_MESSAGE_MAP(CGenericWindow, CFrameWnd)

ON_WM_LBUTTONDOWN()

END_MESSAGE_MAP()

Void CGenericWindow::OnLButtonDown(UINT nFlags, Cpoint point) {

MessageBox( ³Left mouse button pressed«´, NULL, MB_OK);

}

BOOL CGenericApp::InitInstance() {

m_pMainWnd = new CGenericWindow();

m_pMainWnd->ShowWindow(m_nCmdShow);

m_pMainWnd->UpdateWindow();

return TRUE;

}

CGenericApp GenericApp;




Analysis..

This program looks different from a C/SDK program

± The WinMain() function is gone, and

± There is no code that seems to be registering the window

classes

There is no message handling function anywhere

± It seems the message loop hasn¶t been created

Most of the implementation details have been hidden

from the programmer ± The framework does most of the job for the programmer and

have been hidden inside macros likeBEGIN_MESSAGE_MAP




..Analysis

WinMain() is part of the application framework andMFC¶s

± WinMain() does a very good job initializing the variables,creating the window and setting up the message loop

The function InitInstance() is called by the WinMain()

± Handles the creation of the window and registers thewindow classes too

MFC¶s message handling still uses the same functions

GetMessage(), TranslateMessage() andDispatchMessage()

± But at the lowest level because these functions have beenencapsulated




The IDE

To start a new MFC project«




The IDE

There are many options in the following dialogs, but for

the time being, choose

± Choose ³Dialog Based´ & Check ³Windows Sockets´




The IDE

Now you have

± C++ files & differentclasses for your project

± Basic GUI Resourcesfile




The IDE

The Resource Editor

Visual Studio IDE provides us with

WYSIWYG editor to generate the

definition file for us.




The IDE

Know the class

structure

The application class

The Dialog¶s (GUI) class

Start your code here




The IDE

Adding components in the generated dialog

Select UI

controls

here

To view/add/edit

messages,

handler functions,

member variables by

ClassWizard




The IDE

View/Add Event Handlers




The IDE

Adding event handler functions

± After double clicking on the button, the IDE helps you toregister a listener function that handles BN_CLICKED

message

Add your

codes for

handling click

event here




References

MSDN Online

Beginning Visual C++ 6

± Ivor Horton, Wrox Publication

Learn Microsoft Visual C++ 6.0 Now

± Chuck Sphar, Microsoft Press

Samples ± min

± appwiz

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