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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"><HTML><HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html;CHARSET=iso-8859-1"><SCRIPT LANGUAGE="JavaScript"><!--function popUp(pPage) { var fullURL = document.location; var textURL = fullURL.toString(); var URLlen = textURL.length; var lenMinusPage = textURL.lastIndexOf("/"); lenMinusPage += 1; var fullPath = textURL.substring(0,lenMinusPage); popUpWin = window.open('','popWin','resizable=yes,scrollbars=no,width=525,height=394'); figDoc= popUpWin.document; zhtm= '<HTML><HEAD><TITLE>' + pPage + '</TITLE>'; zhtm += '</head>'; zhtm += '<BODY bgcolor="#FFFFFF">'; zhtm += '<IMG SRC="' + fullPath + pPage + '">'; zhtm += '<P><B>' + pPage + '</B>'; zhtm += '</BODY></HTML>'; window.popUpWin.document.write(zhtm); window.popUpWin.document.close(); // Johnny Jackson 4/28/98 }//--> </SCRIPT><link rel="stylesheet" href="/includes/stylesheets/ebooks.css"> <META NAME="GENERATOR" Content="Symantec Visual Page Mac 1.1.1"> <TITLE>Teach Yourself Visual C++ 6 in 21 Days -- Ch 11 -- Creating Multiple Document Interface Applications8</TITLE></HEAD><BODY TEXT="#000000" BGCOLOR="#FFFFFF"><H1 ALIGN="CENTER"><IMG SRC="../button/sams.gif" WIDTH="171" HEIGHT="66" ALIGN="BOTTOM"BORDER="0"><BR>Teach Yourself Visual C++ 6 in 21 Days</H1><CENTER><P><A HREF="../ch10/ch10.htm"><IMG SRC="../button/previous.gif" WIDTH="128" HEIGHT="28"ALIGN="BOTTOM" ALT="Previous chapter" BORDER="0"></A><A HREF="../ch12/ch12.htm"><IMGSRC="../button/next.gif" WIDTH="128" HEIGHT="28" ALIGN="BOTTOM" ALT="Next chapter"BORDER="0"></A><A HREF="../index.htm"><IMG SRC="../button/contents.gif" WIDTH="128"HEIGHT="28" ALIGN="BOTTOM" ALT="Contents" BORDER="0"></A> <HR></CENTER><H1 ALIGN="CENTER">- 11 -<BR>Creating Multiple Document Interface Applications</H1><H1></H1><UL> <LI><A HREF="#Heading1">What Is an MDI Application?</A> <LI><A HREF="#Heading2">Creating an MDI Drawing Program</A> <UL> <LI><A HREF="#Heading3">Building the Application Shell</A> <LI><A HREF="#Heading4">Building the Drawing Functionality</A> <LI><A HREF="#Heading5">Adding Menu Handling Functionality</A> </UL> <LI><A HREF="#Heading6">Adding a Context Menu</A> <LI><A HREF="#Heading7">Summary</A> <LI><A HREF="#Heading8">Q&A</A> <LI><A HREF="#Heading9">Workshop</A> <UL> <LI><A HREF="#Heading10">Quiz</A> <LI><A HREF="#Heading11">Exercise</A> </UL></UL><P><HR SIZE="4"><BR>Today, you will learn how to build Multiple Document Interface (MDI) applicationsusing Visual C++. You will be able to build applications that allow users to workon multiple documents at one time, switching between the windows of the applicationto do their work. In this chapter, you will learn</P><P><UL> <LI>The difference between SDI and MDI applications. <P> <LI>How to create an MDI application. <P> <LI>How to send multiple menu entries to a single event-handling function. <P> <LI>How to add a context menu to a Document/View style application.</UL><H2><A NAME="Heading1"></A>What Is an MDI Application?</H2><P>As far as coding an MDI application with Visual C++, there's little differencebetween creating an SDI and an MDI application. However, when you get deeper intothe two application styles, you'll find quite a few differences. Although an SDIapplication allows the user to work on only one document at a time, it also normallylimits the user to working on a specific type of document. MDI applications not onlyenable the user to work on multiple documents at the same time, but also MDI applicationscan allow the user to work on multiple types of documents.</P><P>An MDI application uses a window-in-a-window style, where there is a frame windowaround one or more child windows. This is a common application style with many popularsoftware packages, including Word and Excel.</P><P>Architecturally, an MDI application is similar to an SDI application. In fact,with a simple MDI application, the only difference is the addition of a second frameclass to the other classes that the AppWizard creates, as shown in Figure 11.1. Asyou can see, the Document/View architecture is still very much the approach you usefor developing MDI applications as well as SDI applications.</P><P><A HREF="javascript:popUp('11fig01.gif')"><B>FIGURE 11.1.</B></A><B> </B><I>TheMDI Document/ View architecture.</I></P><P>When you create an MDI application, you will create just one more class than youcreated with an SDI application. The classes are</P><P><UL> <LI>The CWinApp derived class <P> <LI>The CMDIFrameWnd derived class <P> <LI>The CMDIChildWnd derived class <P> <LI>The CDocument derived class <P> <LI>The CView derived class</UL><P>The two MDI derived classes, CMDIFrameWnd (the CMainFrame class in your project)and CMDIChildWnd (the CChildFrame class in your project), are the only two classesthat are different from the SDI application that you created.</P><P>The first of these two classes, the CMDIFrameWnd-derived CMainFrame, is the mainframe of the application. It provides an enclosed space on the desktop within whichall application interaction takes place. This frame window is the frame to whichthe menu and toolbars are attached.</P><P>The second of these two classes, the CMDIChildWnd-derived CChildFrame class, isthe frame that holds the CView class. It is the frame that passes messages and eventsto the view class for processing or display.</P><P>In a sense, the functionality of the frame class in the SDI application has beensplit into these two classes in an MDI application. There is additional support forrunning multiple child frames with their own document/view class instances at thesame time.</P><P><H2><A NAME="Heading2"></A>Creating an MDI Drawing Program</H2><P>To get a good understanding of just how alike the Document/View architecturesare for the SDI and MDI applications, today you will implement that same drawingapplication that you created yesterday, only this time as an MDI application.</P><P><H3><A NAME="Heading3"></A>Building the Application Shell</H3><P>To create the application shell for today's application, follow these steps:</P><P><DL> <DT></DT> <DD><B>1. </B>Create a new AppWizard project. Name the project <B>Day11</B>. <P> <DT></DT> <DD><B>2. </B>On the first step of the AppWizard, select Multiple Documents, as shown in Figure 11.2. <P></DL><P><A HREF="javascript:popUp('11fig02.gif')"><B>FIGURE 11.2.</B></A><B> </B><I>Specifyingan MDI application.</I></P><P><I></I><DL> <DT><I></I></DT> <DD><B>3. </B>Use the default values on the second step of the AppWizard. <P> <DT></DT> <DD><B>4. </B>On the third step of the AppWizard, uncheck the support for ActiveX Controls. <P> <DT></DT> <DD><B>5. </B>On the fourth step of the AppWizard, leave all the default values. Click the Advanced button. <P> <DT></DT> <DD><B>6. </B>In the Advanced Options dialog, enter a three-letter file extension for the files that your application will generate (for example, dhc or dvp). Click the Close button to close the dialog and then click Next to move to the next step of the AppWizard. <P> <DT></DT> <DD><B>7. </B>Use the default settings on the fifth step of the AppWizard. <P> <DT></DT> <DD><B>8. </B>On the sixth and final AppWizard step, leave the base class as CView and click Finish. The AppWizard generates the application shell. <P></DL><H3><A NAME="Heading4"></A>Building the Drawing Functionality</H3><P>Because you are creating the same application that you created yesterday, onlyas an MDI application this time, you need to add the same functionality to the applicationthat you added yesterday. To save time, and to reemphasize how alike these two applicationarchitectures are, perform the same steps you did yesterday to create the CLine classand add the functionality to the CDay11Doc and CDay11View classes. Add the supportinto the CDay11Doc and CLine classes for selecting colors and widths, but do notadd any menu event message handlers or create the color menu. When you finish addingall that functionality, you should have an application in which you can open multipledrawings, all drawing with only the color black.</P><BLOCKQUOTE> <P><HR><STRONG>CAUTION:</STRONG> Because you haven't created the menus yet, and the color initialization uses the color menu IDs, you will probably have to hard-code the initialization of the color to 0 to get your application to compile. Once you add the color menu, the menu IDs should have been added, so you will be able to return to using the IDs in your code. For the time being, change the line of code in the OnNewDocument function in the CDay11Doc class from <PRE> m_nColor = ID_COLOR_BLACK - ID_COLOR_BLACK;</PRE></BLOCKQUOTE><PRE></PRE><BLOCKQUOTE> <P>to<BR> m_nColor = 0;<BR> You will also need to make the same sort of change to the GetColor function because it uses one of the color menu IDs also.<HR></BLOCKQUOTE><H3><A NAME="Heading5"></A>Adding Menu Handling Functionality</H3><P>Now that you've got all the functionality in your application, you would probablylike to add the color menu so you can use all those available colors in your drawings.When you expand the Resource View tree and look in the Menu folder, you'll find notone, but two menus defined. Which one do you add the color menu to?</P><P>The IDR_MAINFRAME menu is the menu that is available when no child windows areopen. If you run your application and close all child windows, you'll see the menuchange, removing all the menus that apply to child windows. Once you open anotherdocument, either by creating a new document or by opening an existing document, themenu changes back, returning all the menus that apply to the documents.</P><P>The IDR_DAY11TYPE menu is the menu that appears when a child window is open. Thismenu contains all the functions that apply to documents. Therefore, this is the menuthat you need to add the color menu to. Add the color menu by following the samedirections as yesterday, using the same menu properties.</P><P>Once you add all the menus, you need to add the menu event handlers. Today, youare going to take a different approach to implementing the menu event handlers thanyou did yesterday. The Q&A section at the end of yesterday's chapter had a discussionof using a single event-handler function for all the color menus. That is what youare going to implement today. Unfortunately, the Class Wizard doesn't understandhow to route multiple menu event messages to the same function correctly, so you'regoing to implement this yourself by following these steps:</P><P><DL> <DT></DT> <DD><B>1. </B>Open the Day11Doc.h header file. <P> <DT></DT> <DD><B>2. </B>Scroll down toward the bottom of the header file until you find the protected section where the AFX_MSG message map is declared (search for //{{AFX_MSG(CDay11Doc)). <P> <DT></DT> <DD><B>3. </B>Add the function declarations in Listing 11.1 before the line that you searched for. (The string that you searched for is the beginning marker for the Class Wizard maintained message map. Anything you place between it and the end marker, //}}AFX_MSG, is likely to be removed or corrupted by the Class Wizard.) <P></DL><H4>LISTING 11.1. THE EVENT-HANDLER DECLARATIONS IN Day11Doc.h.</H4><PRE>... 1: #ifdef _DEBUG 2: virtual void AssertValid() const; 3: virtual void Dump(CDumpContext& dc) const; 4: #endif 5: 6: protected: 7: 8: // Generated message map functions 9: protected:10: afx_msg void OnColorCommand(UINT nID);11: afx_msg void OnUpdateColorUI(CCmdUI* pCmdUI);12: //{{AFX_MSG(CDay11Doc)13: // NOTE - the ClassWizard will add and remove member functions Âhere.14: // DO NOT EDIT what you see in these blocks of generated Âcode !15: //}}AFX_MSG16: DECLARE_MESSAGE_MAP()17: private:18: UINT m_nColor;19: CObArray m_oaLines;</PRE><PRE>20: };</PRE><P><DL> <DT></DT> <DD><B>4. </B>Open the Day11Doc.cpp source-code file.⌨️ 快捷键说明
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