Microsoft Foundation Classes

1
Microsoft Foundation Classes
2
Objectives

• In this chapter you will learn
• About Microsoft Foundation Class programming
• How to write basic MFC programs
• How to work with resources
• About the CString class
• How to create dialog-based applications
• How to work with message maps
• How to build an application framework with the
  MFC Application Wizard

3
Microsoft Foundation Classes

• The Microsoft Foundation Classes or MFC is a
  class library that assists programmers in
  creating Windows-based applications
• Perhaps two of the most important aspects of MFC
  programming are
• MFC adds object-oriented programming capabilities
  to Windows API programming
• MFC encapsulates the Windows API into a logically
  organized hierarchy

4
Microsoft Foundation Classes

• One of Microsofts main goals in designing MFC
  was to create a C object-oriented class library
  for building Windows API applications
• Prior to MFC programmers had to design their
  programs so that they conformed to the C language
  requirements of the Windows API
• This means that they could not use the
  object-oriented capabilities of C which are
  not found in C
• Visual C is designed to make writing MFC
  programs a relatively easy process

5
Microsoft Foundation Classes

• When you use Visual C to write an MFC program
  you first use the MFC Application Wizard to walk
  you through the steps involved in creating an MFC
  application
• After running MFC Application Wizard Visual C
  provides something called the Microsoft
  Foundation Class framework or MFC framework for
  short which is basically a skeleton application
  created from MFC classes that you can use as a
  basis for your program

6
Microsoft Foundation Classes

• A hook is a location in a program where a
  programmer can insert code that adds
  functionality
• Visual C provides plenty of comments to help
  you find the hooks

7
MFC Class Library

• The MFC class library consists of two major
  sections
• The MFC class hierarchy
• Global functions and macros

8
MFC Class Hierarchy

• The simple class hierarchy examples you saw in
  Chapter 8 were relatively small
• In contrast the MFC class hierarchy is
  surprisingly large
• The MFC class library contains over two hundred
  classes
• Figure 10-5 shows a partial listing of the class
  hierarchy highlighting some of the more
  important classes

9
Partial Listing of the MFC Class Hierarchy
10
MFC Class Hierarchy

• Most classes in the MFC class hierarchy derive
  from the CObject base class
• The most important branch of the MFC class
  hierarchy is the CCmdTarget class which
  encapsulates the messaging features of the
  Windows API
• The CWinApp class also known as the application
  class is responsible for initializing starting
  running and stopping an MFC windows application

11
MFC Class Hierarchy

• The CWnd class encapsulates the various Windows
  API functions data types and other code used
  for creating and instantiating windows
• Derived from the CWnd class are more specialized
  types of window classes such as the CFrameWnd
  class which creates a standard type of window
  known as a frame window and the CDialog class
  for creating dialog boxes

12
Global Functions

• If a function is not a member of an MFC class
  then it is a global function that is available to
  all MFC classes regardless of their position in
  the MFC class hierarchy
• All MFC global functions begin with a prefix of
  Afx
• Figure 10-6 shows an example of a message box
  created with the AfxMessageBox() function

13
Macros

• A programming element that is commonly used in
  MFC programming is a macro
• A macro represents C code constants and other
  programming elements and is defined using the
  define preprocessor directive
• A macro in C is a name that represents C code
  and other programming elements that you would
  like to execute simply by calling the macro name
  similar to the way you call a function name

14
Macros

• During preprocessing a macro name is replaced by
  the code and other programming elements that it
  represents
• This process is similar to using the inline
  keyword to request that the compiler replace
  calls to a function with the function definition
  wherever in a program the function is called
• Macro names in the MFC library are in all
  uppercase letters

15
MFC Notation

• All MFC class names begin with C
• Additionally data members of MFC classes are
  prefixed with m_
• Figure 10-7 shows an example of the MFC Class
  Wizard when you add an MFC class named CCalculator

16
Basic MFC Programs

• You can easily create the MFC framework for an
  MFC program using the MFC Application Wizard
• The classes that turn a standard C program into
  an MFC program derive from MFC classes
• By default Win32 application projects do not
  support MFC programming
• In order to enable MFC support in a Win32
  application project you must select the Use MFC
  in a Shared DLL setting in the Use of MFC combo
  box in the General category of the Property Pages
  dialog box

17
The Application Class

• An application class is the starting point of any
  MFC application
• You derive an application class from the CWinApp
  class
• The application class object you instantiate in
  an MFC program represents the application as a
  whole
• When you derive an application object you must
• Override the virtual InitInstance() function
• Instantiate a global object of your application
  class

18
The Application Class

• The InitInstance() function is called by the
  inherited WinMain() function each time a new
  instance of your MFC program starts
• You can instantiate only one global application
  class object and it is usually instantiated
  within the application classs implementation
  file
• Figure 10-10 in the text shows an example of a
  basic application class named CbasicApp

19
The Windows Class

• The class you will use in this section is the
  CFrameWnd class which creates a simple window
  with a frame title bar control menu and
  control buttons
• One task that is required for all window classes
  is calling the inherited Create() function from
  the class constructor
• The Create() function creates the window itself
  when an object of the window class is instantiated

20
The Windows Class

• In standard Windows API programming you use the
  ShowWindow() function to display a window
• MFC programming also uses a ShowWindow() function
  to display windows
• It is important that you understand that in an
  MFC Program the ShowWindow() function is not
  called from the window class
• Instead you call the ShowWindow() function from
  the application classs InitInstance() function
  using an instantiated object of the window class

21
The Windows Class

• An important concept to understand is that
  m_pMainWnd object is not the window itself
• All objects that display windows are not the
  windows themselves
• The window is only a visual representation of the
  object
• To add a window class to the MFC Calculator
  program follow the instructions on pages 533 and
  534 of the textbook

22
Resources

• A resource is a graphical user interface element
  or type of stored information that is used by a
  Windows application
• Figure 10-16 in the text lists the standard
  Windows API resources
• Resources are defined in special files called
  resource scripts
• Resource scripts have an extension of .rc and are
  written in C preprocessor language

23
Resources

• A resource ID is an integer constant declared
  with the define preprocessor directive and is
  used for programmatically referring to a resource
• It is common practice to declare all resource
  constants in an interface file named resource.h
  in order to make it easier to reference them in
  your program
• Visual C automatically creates a resource
  script when you run either the MFC Application
  Wizard or the Add Resource Wizard

24
Add Resource Wizard

• You use the Add Resource Wizard to add new
  resources to an MFC project
• You start the Add Resource Wizard by selecting
  the Add Resource command from the Project menu to
  display the Add Resource dialog box
• Figure 10-17 shows an example of the Add Resource
  dialog box

25
Resource Editors

• Resource editors allow you to quickly create and
  modify resources in a graphical environment
• You can still edit a resource files C
  preprocessor code though Visual C does an
  excellent job of writing the code for you
• Figure 10-19 in the text shows the C preprocessor
  code that represents the same dialog box
• You can also see the Toolbox in Figure 10-18

26
Resource View

• Resource View contains folders representing the
  different resource types
• You can use Resource View to quickly open a
  resource in a resource editor
• To view a resource in its editor expand its
  resource folder and double-click the resource
  name
• Figure 10-20 in the text shows the IDE after
  expanding the Toolbar folder in the Resource View
  tab and double-clicking the IDR_MAINFRAME resource

27
Properties Window

• The Properties window in Visual C (and other
  Visual Studio tools) is used for managing the
  properties of various elements in a project
  including the properties of resources
• Different types of resources have different
  properties available in their Properties window
• Figure 10-21 shows a portion of the Properties
  window for a button in the Dialog Box editor

28
Properties Window for a Button in the Dialog Box
Editor
29
Properties Window

• At the top of the Properties window is the Object
  name combo box which displays the name of the
  currently selected object or objects
• Below the Object name combo box is the Properties
  window toolbar which includes
• A Categorized button which displays all of an
  objects properties by category
• An Alphabetic button which displays all of an
  objects properties alphabetically
• A Properties button which displays an objects
  properties
• A Property Pages button which displays the
  projects Property Pages dialog box

30
Properties Window

• An Events button also appears for any selected
  objects that have associated events
• Visual C treats almost anything including
  class members as a property
• If you need to make any changes to the basic
  declarations (function parameters the data types
  of member variables and so on) in your class
  you have two choices
• You can either make the changes manually in the
  header and source files or you can use the
  Properties window

31
Properties Window

• In order to display a class members properties
  in the Properties window you must select the
  class member in Class View
• Figure 10-22 shows a portion of the Properties
  window for the InitInstance() member function in
  the Ccalculator class
• Notice in Figure 10-22 that InitInstance() is
  selected in Class View

32
Properties Window

• The Properties window toolbar includes two
  additional buttons Messages and Overrides when
  one of the following conditions is true
• When the Code Editor window is the active window
  in the IDE and it is opened to a class interface
  or implementation file
• When Class View is the active window in the ID
  and you have selected a class icon in Class View

33
A Member Function in the Properties Window
34
The CString Class

• The CString class is used for manipulating
  strings in MFC programs and works in much the
  same way as the string class
• You create a string variable with the CString
  class using a statement similar to CString
  myString
• You can also assign a string directly to the
  variable name using a statement such as CString
  myString This is a text string.

35
Dialog-Based Applications

• A dialog box is a window that is used to display
  information or to gather information from users
• The message box you have seen in this chapter is
  an example of a dialog box
• Figure 10-23 shows the Open dialog box that is
  shared by many Windows applications

36
Dialog-Based Applications

• All dialog boxeswhether standard or customare
  created using two components a dialog resource
  and a dialog class derived from the CDialog class
• The dialog resource represents the visual aspect
  of the dialog box and the dialog class provides
  programmatic access to the dialog box
• Applications that use a dialog box as their
  primary interface window are called dialog-based
  applications

37
Dialog-Based Applications

• In order for a class derived from CDialog to know
  which dialog box resource it is associated with
  you must call a parameterized constructor for the
  CDialog base class and pass to it the enum
  variable that represents the dialog box resource
  ID
• An enumerated or enum type declaration allows
  you to create your own data type to which you can
  assign only a series of predefined constant
  integer values

38
Dialog-Based Applications

• You declare an enum type declaration using the
  syntax enum type_name (value1 value2 value3
  )
• The values between the braces are known as
  enumerators and are used for symbolically
  representing a value
• Each enumerator receives an integer value
  starting with 0 for the first enumerator

39
Modal and Modeless Dialog Boxes

• Modal dialog boxes require users to close or
  cancel the dialog box before they can continue
  working with an application
• The message boxes you have worked with are
  examples of modal dialog boxes
• Once a modal message box appears on your screen
  you cannot access any other window in an
  application until you close the message box

40
Modal and Modeless Dialog Boxes

• Figure 10-25 shows the modal Font dialog box for
  WordPad a simple word-processing program
  supplied with Windows operating systems

41
Modal and Modeless Dialog Boxes

• In comparison to a modal dialog box modeless
  dialog boxes do not need to be closed before you
  return to another window in the application
• Modeless dialog boxes function more like frame
  windows and other types of primary application
  windows
• Modeless dialog boxes require quite a bit more
  work than modal dialog boxes

42
Modal and Modeless Dialog Boxes

• Much of the behind-the-scenes work such as
  closing and destroying the dialog window is
  handled automatically with modal dialog boxes
• With modeless dialog boxes however especially
  in dialog-based applications you need to
  override several inherited member functions
• Overriding the inherited member functions allows
  you to correctly close and destroy the dialog
  window

43
Displaying Modal Dialog Boxes

• You display a modal dialog box from an
  applications InitInstance() function the same
  way you display a frame window
• You instantiate an object of the dialog class and
  use the inherited DoModal() function to display
  the modal dialog box
• By default if a user clicks a button containing
  a resource ID of IDOK or IDCANCEL the dialog box
  closes

44
Displaying Modal Dialog Boxes

• The IDOK resource ID represents the OK button
  and the IDCANCEL resource ID represents the
  Cancel button
• The DoModal() function returns an integer value
  representing the resource ID that caused the
  dialog box to close
• You use these resource IDs in an if statement to
  take the appropriate action depending on whether
  the user pressed the OK button or the Cancel
  button

45
Working with Controls

• Dialog boxes typically contain groups of controls
  through which a user interacts with an
  application
• Controls are user interface items such check
  boxes command buttons text boxes and other
  objects
• You add controls to a dialog box by using the
  Controls toolbar in the Dialog Editor

46
Working with Controls

• You can add the following three types of controls
  to MFC programs
• Windows common controls
• MFC controls
• ActiveX controls
• Windows common controls are the standard
  controls such as edit boxes buttons check
  boxes and so on you see in common dialog boxes

47
Working with Controls

• MFC controls are provided by MFC and are not part
  of the Widows operating system
• There are three MFC controls the Bitmap Button
  control the Checklist Box control and the Drag
  List Box control
• ActiveX is a technology that allows programming
  objects to be easily reused with any programming
  language that supports Microsofts Component
  Object Model
• The Component Object Model or COM is an
  architecture for cross-platform development of
  client/server applications

48
Working with Controls

• ActiveX controls are objects that are placed in
  Web pages or inside programs created with
  COM-enabled programming languages
• ActiveX controls are very popular in Windows
  programming you can literally find thousands of
  types of ActiveX controls in various places on
  the Web
• Figure 10-29 in the text lists the Windows common
  controls along with a description of each
  control and its associated MFC class

49
Working with Controls

• You do not usually need to derive classes for
  individual controls placed on a dialog box
• More complex types of controls must be controlled
  using an associated MFC class
• To add controls to the MFC Calculator programs
  dialog resource perform the steps listed on
  pages 552 and 553 of the textbook

50
Dialog Data Exchange

• To set and retrieve control values in an MFC
  application you can use the same SetWindowText()
  and GetWindowText() Windows API functions that
  you learned about in Chapter 8
• MFC provides a special mechanism however called
  dialog data exchange or DDX to handle the
  exchange of values between controls and variables
• You do not need to call the SetWindowText() and
  GetWindowText() functions in an MFC program
  because DDX handles the exchange of information
  for you

51
Dialog Data Exchange

• A related mechanism called dialog data
  validation or DDV assists in the validation of
  data as it is exchanged between controls and
  variables
• Before you can use DDX or DDV you must first
  override the DoData Exchange() function in the
  class derived from CDialog that is associated
  with your dialog resource ID
• Figure 10-32 in the text shows an example of the
  Add Member Variable Wizard dialog box with the
  Control variable check box selected

52
Dialog Data Exchange

• The UpdateDate() function either initializes
  dialog box controls using associated data
  members or it copies the current control values
  back into the associated data members
• The UpdateData() function calls the
  DoDataExchange() function when it is passed a
  value of FALSE by the OnInitDialog() function
• Add a DDX data member to the MFC Calculator
  program using the procedures shown on page 556 of
  the textbook

53
Message Maps

• A message map associates messages with message
  handler functions
• All windows derived from CCmdTarget can include
  message maps
• Because CWnd derives from CCmdTarget any of the
  child class windows of CWnd can include their own
  message maps
• You add a message map to a window by first adding
  the DECLARE_MESSAGE_MAP() macro to the class
  interface file

54
Message Maps

• You must add a message map block to the class
  implementation file starting with the
  BEGIN_MESSAGE_MAP() macro and ending with the
  END_MESSAGE_MAP() macro
• One of the more common message macros you will
  use is the ON_COMMAND macro which represents the
  events that are raised when a user selects a menu
  option or presses a shortcut key
• The ON_COMMAND macro takes two parameters a
  resource ID and the name of a message handler
  function

55
Message Maps

• To give the MFC Calculator program its
  functionality you will use the BN_CLICKED macro
  which is raised for the BN_CLICKED event
• The Event Handler Wizard provides an automated
  way of associating a dialog control with an event
• You use the Event Handler Wizard by highlighting
  a dialog control and then by selecting Add Event
  Handler from the Menu submenu on the Edit menu
• Figure 10-34 in the text shows an example of the
  Event Handler Wizard dialog box

56
Building an Application Wizard Framework with
the MFC Application Wizard

• You have now examined several of the most
  important pieces of an MFC framework
• Although there are other important aspects of the
  MFC framework that you still need to explore at
  this point you should be able to understand the
  parts of a simple dialog-based application
  created with the MFC Application Wizard
• After you create the dialog-based application
  using the MFC Application Wizard you still might
  not recognize much of what you see in the MFC
  framework

57
Building an Application Wizard Framework with
the MFC Application Wizard

• Much of the MFC framework code is automatically
  created when you run the MFC Class Wizard so you
  do not need to worry about it
• One important aspect of MFC programs that you
  will not find in the MFC Class Wizard generated
  program is AfxWin.h include files
• To create a dialog-based application using the
  MFC Application Wizard use the procedures
  illustrated on pages 566 and 567 of the textbook

58
Summary

• The Microsoft Foundation Classes or MFC is a
  class library that helps programmer create
  Windows-based applications
• A hook is a location in a program where a
  programmer can insert code that enhances
  functionality
• The CWinApp class also known as the application
  class is responsible for initializing starting
  running and stopping an MFC windows application

59
Summary

• The CWnd class encapsulates the various Windows
  API functions data types and other code used
  for creating and instantiating windows
• The MFC classes that derive from the CWnd class
  are used for creating the different types of
  windows that are visible to the user
• A resource is a graphical user interface element
  or type of stored information that is used by a
  Windows application

60
Summary

• Applications that use a dialog box as their
  primary interface window are called dialog-based
  applications
• MFC provides a special mechanism called dialog
  data exchange or DDX to handle the exchange of
  values between controls and variables
• Much of the MFC framework code is automatically
  created when you run the MFC Class Wizard