chap3_4.htm

着重介绍基于C++的web编程技术

    <p ALIGN="JUSTIFY">return nReturnCode;</p>
    <p ALIGN="JUSTIFY">}</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">应用程序执行时，</font><font FACE="Times New Roman" SIZE="3">Windows</font><font SIZE="3">自动调用应用程序框架内部的</font><font FACE="Times New Roman" SIZE="3">WinMain</font><font SIZE="3">函数。如清单</font><font FACE="Times New Roman" SIZE="3">3-1</font><font SIZE="3">所示，</font><font FACE="Times New Roman" SIZE="3">WinMain</font><font SIZE="3">函数会查找该应用程序的一个全局构造对象，这个对象是由</font><font FACE="Times New Roman" SIZE="3">CWinApp</font><font SIZE="3">派生类构造的，有且只有一个。它是一个全局对象，因此在程序启动时，它就已经被构造好了。</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">随后，</font><font FACE="Times New Roman" SIZE="3">WinMain</font><font SIZE="3">将调用这个对象的</font><font FACE="Times New Roman" SIZE="3">InitApplication</font><font SIZE="3">和</font><font FACE="Times New Roman" SIZE="3">InitInstance</font><font SIZE="3">成员函数，完成应用程序实例的初始化工作。随后，</font><font FACE="Times New Roman" SIZE="3">WinMain</font><font SIZE="3">调用</font><font FACE="Times New Roman" SIZE="3">Run</font><font SIZE="3">成员函数，运行应用程序的消息循环。在程序结束时，</font><font FACE="Times New Roman" SIZE="3">WinMain</font><font SIZE="3">调用</font><font FACE="Times New Roman" SIZE="3">AfxWinTerm</font><font SIZE="3">函数，做一些清理工作。</font><font FACE="Times New Roman" SIZE="3"></p>
    <b><p ALIGN="JUSTIFY"></b></font><font color="#3973DE" FACE="Times New Roman" SIZE="3">3.4.2 
    </font><font SIZE="3" color="#3973DE">应用程序类</font><font FACE="Times New Roman" SIZE="3"></p>
    <b><p ALIGN="JUSTIFY"></b></font><font SIZE="3">每个应用程序必须从</font><font FACE="Times New Roman" SIZE="3">CWinApp</font><font SIZE="3">派生出自己的应用程序类，并定义一个全局的对象。该应用程序类包含了</font><font FACE="Times New Roman" SIZE="3">Windows</font><font SIZE="3">下应用程序的初始化、运行和结束过程。基于框架建立的应用程序必须有一个（且只能有一个）从</font><font FACE="Times New Roman" SIZE="3">CWinApp</font><font SIZE="3">派生的类的对象。在</font><font FACE="Times New Roman" SIZE="3">Hello</font><font SIZE="3">程序中，我们从</font><font FACE="Times New Roman" SIZE="3">CWinApp</font><font SIZE="3">中派生出一个</font><font FACE="Times New Roman" SIZE="3">CHelloApp</font><font SIZE="3">类，并定义了一个全局对象</font><font FACE="Times New Roman" SIZE="3">theApp</font><font SIZE="3">。</font><font FACE="Times New Roman" SIZE="3">CHelloApp</font><font SIZE="3">类在</font><font FACE="Times New Roman" SIZE="3">hello.cpp</font><font SIZE="3">中定义。</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">要访问应用程序类构造的对象，可以调用全局函数</font><font FACE="Times New Roman" SIZE="3">AfxGetApp()</font><font SIZE="3">。</font><font FACE="Times New Roman" SIZE="3">AfxGetApp()</font><font SIZE="3">返回一个指向全局对象的指针。可以通过对它进行强制类型转换，转换为我们派生的应用程序类。</p>
    <p ALIGN="JUSTIFY">比如：</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">CHelloApp* pApp=(CHelloApp*)AfxGetApp()</font><font SIZE="3">；</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">在</font><font FACE="Times New Roman" SIZE="3">CHelloApp</font><font SIZE="3">应用程序类中，我们还重载了</font><font FACE="Times New Roman" SIZE="3">CWinApp</font><font SIZE="3">的成员函数</font><font FACE="Times New Roman" SIZE="3">InitInstance</font><font SIZE="3">。</font><font FACE="Times New Roman" SIZE="3">InitInstance</font><font SIZE="3">函数主要完成以下工作：设置注册数据库，载入标准设置（最近打开文件列表等）、注册文档模板。其中注册文档模板过程中隐含地创建了主窗口。接着，处理命令行参数，显示窗口，然后返回、进入消息循环。下面的程序清单</font><font FACE="Times New Roman" SIZE="3">3.2</font><font SIZE="3">给出了</font><font FACE="Times New Roman" SIZE="3">Hello</font><font SIZE="3">程序的</font><font FACE="Times New Roman" SIZE="3">InitInstance</font><font SIZE="3">函数代码。</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY"></font><b><font SIZE="3">　</p>
    <p ALIGN="JUSTIFY">清单</font><font FACE="Times New Roman" SIZE="3">3.2 InitInstance</font><font SIZE="3">函数</font></b><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">// CHelloApp initialization</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">BOOL CHelloApp::InitInstance()</p>
    <p ALIGN="JUSTIFY">{</p>
    <p ALIGN="JUSTIFY">AfxEnableControlContainer();</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">// Standard initialization</p>
    <p ALIGN="JUSTIFY">// If you are not using these features and wish to reduce the size</p>
    <p ALIGN="JUSTIFY">// of your final executable, you should remove from the following</p>
    <p ALIGN="JUSTIFY">// the specific initialization routines you do not need.</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">#ifdef _AFXDLL</p>
    <p ALIGN="JUSTIFY">Enable3dControls(); // Call this when using MFC in a shared DLL</p>
    <p ALIGN="JUSTIFY">#else</p>
    <p ALIGN="JUSTIFY">Enable3dControlsStatic(); // Call this when linking to MFC statically</p>
    <p ALIGN="JUSTIFY">#endif</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">// Change the registry key under which our settings are stored.</p>
    <p ALIGN="JUSTIFY">// You should modify this string to be something appropriate</p>
    <p ALIGN="JUSTIFY">// such as the name of your company or organization.</p>
    <p ALIGN="JUSTIFY">SetRegistryKey(_T(&quot;Local AppWizard-Generated Applications&quot;));</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">LoadStdProfileSettings(); // Load standard INI file options (including 
    MRU)</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">// Register the application's document templates. Document templates</p>
    <p ALIGN="JUSTIFY">// serve as the connection between documents, frame windows and views.</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">CSingleDocTemplate* pDocTemplate;</p>
    <p ALIGN="JUSTIFY">pDocTemplate = new CSingleDocTemplate(</p>
    <p ALIGN="JUSTIFY">IDR_MAINFRAME,</p>
    <p ALIGN="JUSTIFY">RUNTIME_CLASS(CHelloDoc),</p>
    <p ALIGN="JUSTIFY">RUNTIME_CLASS(CMainFrame), // main SDI frame window</p>
    <p ALIGN="JUSTIFY">RUNTIME_CLASS(CHelloView));</p>
    <p ALIGN="JUSTIFY">AddDocTemplate(pDocTemplate);</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">// Parse command line for standard shell commands, DDE, file open</p>
    <p ALIGN="JUSTIFY">CCommandLineInfo cmdInfo;</p>
    <p ALIGN="JUSTIFY">ParseCommandLine(cmdInfo);</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">// Dispatch commands specified on the command line</p>
    <p ALIGN="JUSTIFY">if (!ProcessShellCommand(cmdInfo))</p>
    <p ALIGN="JUSTIFY">return FALSE;</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">// The one and only window has been initialized, so show and update it.</p>
    <p ALIGN="JUSTIFY">m_pMainWnd-&gt;ShowWindow(SW_SHOW);</p>
    <p ALIGN="JUSTIFY">m_pMainWnd-&gt;UpdateWindow();</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">　</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY">return TRUE;</p>
    <p ALIGN="JUSTIFY">}</p>
    <p ALIGN="JUSTIFY"></font><font SIZE="3">在</font><font FACE="Times New Roman" SIZE="3">CWinApp</font><font SIZE="3">的派生类中，必须重载</font><font FACE="Times New Roman" SIZE="3">InitInstance</font><font SIZE="3">函数，因为</font><font FACE="Times New Roman" SIZE="3">CWinApp</font><font SIZE="3">并不知道应用程序需要什么样的窗口，它可以多文档窗口、单文档窗口，也可以是基于对话框的。</font><font FACE="Times New Roman" SIZE="3"></p>
    <b><p ALIGN="JUSTIFY">Run</font><font SIZE="3">成员函数</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="JUSTIFY"></b>WinMain</font><font SIZE="3">在初始化应用程序实例后，就调用</font><font FACE="Times New Roman" SIZE="3">Run</font><font SIZE="3">函数来处理消息循环。</font><font FACE="Times New Roman" SIZE="3">Run</font><font SIZE="3">成员函数不断执行消息循环，检查消息队列中有没有消息。如果有消息，</font><font FACE="Times New Roman" SIZE="3">Run</font><font SIZE="3">将其派遣，交由框架去处理，然后返回继续消息循环。如果没有消息，</font><font FACE="Times New Roman" SIZE="3">Run</font><font SIZE="3">将调用</font><font FACE="Times New Roman" SIZE="3">OnIdle</font><font SIZE="3">来做用户或框架可能需要在空闲时才做的工作，象后面我们讲到的用户接口更新消息处理等。如果既没有消息要处理，也没有空闲时的处理工作要做，则应用程序将一直等待，直到有事件发生。当应用程序结束时，</font><font FACE="Times New Roman" SIZE="3">Run</font><font SIZE="3">将调用</font><font FACE="Times New Roman" SIZE="3">ExitInstance</font><font SIZE="3">。消息循环的流程图如图</font><font FACE="Times New Roman" SIZE="3">3-10</font><font SIZE="3">所示。</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="center"></font><img src="T3_10.gif" alt="T3_10.tif (197232 bytes)" WIDTH="338" HEIGHT="436"><font SIZE="3"></p>
    <p ALIGN="CENTER">图</font><font FACE="Times New Roman" SIZE="3">3-10 Run</font><font SIZE="3">成员函数的消息循环</font><font FACE="Times New Roman" SIZE="3"></p>
    <p ALIGN="CENTER"></font><b><font SIZE="3">　</p>
    <p>关闭应用程序</font><font FACE="Times New Roman" SIZE="3"></p>
    <p></font></b><font SIZE="3">用户可以通过选择</font><font FACE="Times New Roman" SIZE="3">File-Exit</font><font SIZE="3">菜单或点主窗口的关闭按钮，关闭主框架窗口，来终止应用程序。此时，应用程序类首先删除</font><font FACE="Times New Roman" SIZE="3">m_pMainWnd</font><font SIZE="3">主框架窗口对象，然后退出</font><font FACE="Times New Roman" SIZE="3">Run</font><font SIZE="3">函数，进而退出</font><font FACE="Times New Roman" SIZE="3">WinMain</font><font SIZE="3">，在退出</font><font FACE="Times New Roman" SIZE="3">WinMain</font><font SIZE="3">后删除</font><font FACE="Times New Roman" SIZE="3">TheApp</font><font SIZE="3">对象。</font><font FACE="Times New Roman" SIZE="3"></p>
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