Microsoft Visual C++ .NET Professional Projects - Premier Press

Working with Dialog Boxes and

Controls

Dialog boxes are mostly used as extensions of menus. This implies that dialog boxes are used to accept any additional information besides choosing the appropriate menu option. For instance, while working in Microsoft Word, if you choose

Y L options, such as options to select theFtype of line to be drawn (for example, dot-

File, Save, the Save As dialog box is displayed, which accepts information such as

the file name. Similarly, considering the application for which you designed the

Draw menu option, you might customize it further by providing additional

ted or straight line, the color to be used, and the length and thickness of the line). To provide such additional features, you use dialog boxes. In most cases, dialog boxes consist of the user interface that is similar to a form. You can use various

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Figure 4-3 displays the Print dialog box, which is a classic example of a Microsoft Windows dialog box containing several of the different controls listed in Table 4-1.

In any application, you can use three types of dialog boxes:

Application modal dialog box. Has the control of the application in which it is displayed.

This implies that you cannot continue working with the current application until you dismiss the dialog box. Once again taking the example of the Save As dialog box, do you ever remember typing text while this dialog box is open? The same applies to many other dialog boxes, such as the Print and Open dialog boxes. All of these dialog boxes are examples of the application modal dialog box. Although you can’t interact with the current application in which the modal dialog box is open, you can continue working with the other active applications.

FIGURE 4-3 The Print dialog box with different controls

CEditView class and hence will have the basic functionality of a text editor. You’ll learn more about MDI applications and the view classes in Chapter 5.

Creating a Dialog Box Resource

To create a dialog box resource for this example, you need to perform the following steps:

1.Create an MDI application using the MFC Application Wizard. The sample application shown here is named DialogApp. In the left frame of the wizard, click Generated classes and change the base class of

CDialogAppView to CEditView.

2.Switch to the Resource View of the application and, from the list of resources, select Dialog. By default, the wizard provides a dialog box,

IDD_ABOUTBOX. As the name indicates, it displays information about the application itself.

3.Select Project, Add Resource to open the Add Resource dialog box. From the list of resources, select Dialog. The Dialog Resource type provides some predefined layouts for different dialog resources, such as layouts for form view, dialog bar, and property pages. You can either use these predefined resources or create a new one for an application.

4.Click on the New button to create a new dialog resource. A new dialog resource with an ID of IDD_DIALOG1 is added to your application. The dialog box consists of the default OK and Cancel buttons.

5.Add controls to the dialog resource as shown in Figure 4-4. Change captions for the static text controls as shown in the figure, and change the ID of the edit boxes to IDC_LOG and IDC_PASS, respectively. For the password field, change the Password property to True.

In most of the cases, you open a dialog box by using a menu command. So, you will now edit the default menu to add another option that will invoke the dialog box you have created:

1.Click the Menu resource in the Resource Window.

2.Select the menu resource IDR_DialogAppTYPE. Add the option, Logon, as shown in Figure 4-5.

FIGURE 4-4 The dialog resource

FIGURE 4-5 The menu resource

After you have created the resources for the application, the framework for the application is ready to be used. To display the dialog box that you have created, you need to code for the dialog box class. The steps to add a dialog class are detailed next.

Creating a Dialog Box Class

The CDialog class, which is derived from the CWnd class, provides you the functionality for displaying a dialog box and handling messages that are directed to the dialog box. Therefore, for creating any type of dialog box in MFC, you need to

derive a class from the CDialog class. This class provides you with two member functions, DoModal and Create, that you use to display a modal and a modeless dialog box, respectively.

In addition to displaying the dialog box, you also need to enable the dialog box class to handle user interaction with it. This implies that you will have to code to store and retrieve data that the user enters in the dialog box controls. Remember how you did this while using forms in Chapter 3? You had declared member variables corresponding to each of the controls. Similarly, for the controls of the dialog box, you can create member variables that will hold the data. The Add Variable Wizard enables you to add a variable for a control, and the

change function of the CWnd class enables you to exchange data between the controls and the corresponding member variables.

Here’s what you need to do to add a dialog class to your application:

1.Choose Project, Add Class. The MFC Class Wizard, as shown in Figure 4-6, starts.

2.Type “DialogClass” in the Class name box of the wizard and select CDialog from the base class list.

3.Click on the Finish button to close the wizard. The wizard adds two files to your project, DialogClass.h and DialogClass.cpp, which contain the class declaration and definition, respectively.

FIGURE 4-6 The MFC Class Wizard

member variables

DDX_Text(pDX, IDC_LOG,log);

DDX_Text(pDX, IDC_PASS,pass);

}

The DoDataExchange function is a member of the CDialog class. This function accepts a CDataExchange type of object as a parameter. When you create a new dialog class using the AddClassWizard, it automatically overrides the DoDataExchange function of the base class, CDialog.

Finally, before you can use the dialog box functionality, you need to add the appropriate message handlers. All you need to do is the following:

1.In the dialog resource, right-click on the OK button.

2.Select Add Event Handler from the shortcut menu to start the Event Handler Wizard.

3.Click on the Add and Edit button to edit the message handler.

4.Edit the message handler as follows:

void OnBnClickedOk

{

//Call the DDX mechanism UpdateData(TRUE);

MessageBox(“Login name “ + log+” is accepted.”);

//Close the dialog box EndDialog(TRUE);

}

5.Add another message handler for the Cancel button and edit the message handler as follows:

void OnBnClickedCancel()

{

MessageBox(“Closing the dialog box.”);

EndDialog(TRUE);

}

When the user clicks on the OK button, the control is passed to the OnBnClickedOk message handler. In the message handler, the UpdateData function of the CDialog class is invoked. The UpdateData function implements the DDX mechanism by invoking the DoDataExchange function of the CFirstDialog class.

public:

// standard constructor DialogClass(CWnd* pParent = NULL); virtual ~DialogClass();

// enumerator for dialog resource ID

enum { IDD = IDD_DIALOG1 };

protected:

virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support

DECLARE_MESSAGE_MAP()

public:

CString log;

CString pass;

afx_msg void OnBnClickedOk(); afx_msg void OnBnClickedCancel();

};

// DialogClass.cpp file #include “stdafx.h” #include “DialogApp.h” #include “DialogClass.h”

IMPLEMENT_DYNAMIC(DialogClass, CDialog)

DialogClass::DialogClass(CWnd* pParent /*=NULL*/)

: CDialog(DialogClass::IDD, pParent)

,log(_T(“”))

,pass(_T(“”))

{

}

// Destructor DialogClass::~DialogClass()

{

}

void DialogClass::DoDataExchange(CDataExchange* pDX)