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Microsoft Foundation Classes

Microsoft Foundation Classes 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

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Microsoft Foundation Classes

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  1. Microsoft Foundation Classes Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  4. Microsoft Foundation Classes • One of Microsoft’s 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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  7. MFC Class Library • The MFC class library consists of two major sections: • The MFC class hierarchy • Global functions and macros Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  9. Partial Listing of the MFC Class Hierarchy Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 class’s implementation file • Figure 10-10 in the text shows an example of a basic application class named CbasicApp Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 class’s InitInstance() function using an instantiated object of the window class Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  25. Resource Editors • Resource editors allow you to quickly create and modify resources in a graphical environment • You can still edit a resource file’s 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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  28. Properties Window for a Button in the Dialog Box Editor Microsoft Visual C++ .NET Chapter 10

  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 object’s properties by category • An Alphabetic button, which displays all of an object’s properties alphabetically • A Properties button, which displays an object’s properties • A Property Pages button, which displays the project’s Property Pages dialog box Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  31. Properties Window • In order to display a class member’s 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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  33. A Member Function in the Properties Window Microsoft Visual C++ .NET Chapter 10

  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.”; Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  36. Dialog-Based Applications • All dialog boxes—whether standard or custom—are 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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  43. Displaying Modal Dialog Boxes • You display a modal dialog box from an application’s 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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 Microsoft’s Component Object Model • The Component Object Model, or COM, is an architecture for cross-platform development of client/server applications Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

  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 program’s dialog resource, perform the steps listed on pages 552 and 553 of the textbook Microsoft Visual C++ .NET Chapter 10

  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 Microsoft Visual C++ .NET Chapter 10

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