剖析MFC的文档视图结构

/********* 文章系列：MFC技术内幕系列***********//************MFC技术内幕系列之（二）***********//**** 文章题目：MFC文档视图结构内幕 *****//* Copyright(c)2002 bigwhite *//* All rights Reserved *//*********关键字：MFC，文档视图结构************//* 时间：2002.7.23 *//* 注释：本文所涉及的程序源代码均在Microsoft *// Visual Studio.Net Enterprise Architect Edition //* 开发工具包提供的源代码中 *///引 言：侯捷老师的"深入浅出MFC"一书的第8章中有“"Document/View"是MFC的基石。”一说，可以看出文档视图结构在MFC Framework中的地位是多么的重要。本文将以一个标准MFC应用程序向导作成的MDI程序为例，来和大家一起详细挖掘文档视图结构的内幕。正文：//* 1.回顾"InitInstance函数" *//在 我的《MFC应用程序“生死因果”内幕》一文中，当谈到CMyWinApp::InitInstance()时，我只是粗略的讲了介绍了一下各个函数的功 能，而忽略了很多细节，这里让我们在回顾一下CMyWinApp::InitInstance()函数，并将里面与文档视图结构有关的代码深入探讨一下：BOOL CMyApp::InitInstance()//只列出了与文档视图结构相关的源代码{//...//文档模板将用作文档、框架窗口和视图之间的连接CMultiDocTemplate* pDocTemplate;pDocTemplate = new CMultiDocTemplate(IDR_MyTYPE,RUNTIME_CLASS(CMyDoc),RUNTIME_CLASS(CChildFrame), // 自定义 MDI 子框架RUNTIME_CLASS(CMyView));AddDocTemplate(pDocTemplate);// 创建主 MDI 框架窗口CMainFrame* pMainFrame = new CMainFrame;if (!pMainFrame->LoadFrame(IDR_MAINFRAME))return FALSE;m_pMainWnd = pMainFrame;// 仅当具有后缀时才调用 DragAcceptFiles// 在 MDI 应用程序中，这应在设置 m_pMainWnd 之后立即发生// 分析标准外壳命令、DDE、打开文件操作的命令行CCommandLineInfo cmdInfo;ParseCommandLine(cmdInfo);// 调度在命令行中指定的命令。如果// 用 /RegServer、/Register、/Unregserver 或 /Unregister 启动应用程序，则返回 FALSE。if (!ProcessShellCommand(cmdInfo))return FALSE;// 主窗口已初始化，因此显示它并对其进行更新pMainFrame->ShowWindow(m_nCmdShow);pMainFrame->UpdateWindow();return TRUE;}/* 2.初始化文档模板 */分析以下代码：CMultiDocTemplate* pDocTemplate;pDocTemplate = new CMultiDocTemplate(IDR_MyTYPE,RUNTIME_CLASS(CMyDoc),RUNTIME_CLASS(CChildFrame), // 自定义 MDI 子框架RUNTIME_CLASS(CMyView));应用程序首先实例化一个CMultiDocTemplate对象，此过程也是对CMultiDocTemplate类数据成员的初始化过程。按调用次序我列出了以下源代码：注释1: CDocTemplate构造函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcdoctempl.cppCDocTemplate::CDocTemplate(UINT nIDResource, CRuntimeClass* pDocClass,CRuntimeClass* pFrameClass, CRuntimeClass* pViewClass)//部分源代码{ASSERT_VALID_IDR(nIDResource);ASSERT(pDocClass == NULL ||pDocClass->IsDerivedFrom(RUNTIME_CLASS(CDocument)));ASSERT(pFrameClass == NULL ||pFrameClass->IsDerivedFrom(RUNTIME_CLASS(CFrameWnd)));ASSERT(pViewClass == NULL ||pViewClass->IsDerivedFrom(RUNTIME_CLASS(CView)));m_nIDResource = nIDResource;...//m_pDocClass = pDocClass;m_pFrameClass = pFrameClass;m_pViewClass = pViewClass;m_pOleFrameClass = NULL;m_pOleViewClass = NULL;...//}以上为CMultiDocTemplate类的基类CDocTemplate构造函数的部分源代码，该函数初始化了四个重要的成员m_nIDResource，m_pDocClass，m_pFrameClass和m_pViewClass。注释2: CMultiDocTemplate构造函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcdocmulti.cppCMultiDocTemplate::CMultiDocTemplate(UINT nIDResource, CRuntimeClass* pDocClass,CRuntimeClass* pFrameClass, CRuntimeClass* pViewClass): CDocTemplate(nIDResource, pDocClass, pFrameClass, pViewClass){ASSERT(m_docList.IsEmpty());m_hMenuShared = NULL;m_hAccelTable = NULL;m_nUntitledCount = 0; // start at 1// load resources in constructor if not statically allocatedif (!CDocManager::bStaticInit)LoadTemplate();}看完以上代码后，来回过头看一看InitInstance函数将什么参数值传给了CMultiDocTemplate的构造函数。原来是一些RUNTIME_CLASS宏。以下是RUNTIME_CLASS宏的定义:注释3: 以下的宏定义在：..Visual Studio.NETvc7atlmfcincludeafx.h中#define RUNTIME_CLASS(class_name) _RUNTIME_CLASS(class_name)#define _RUNTIME_CLASS(class_name) ((CRuntimeClass*)(&class_name::class##class_name))这个地方是个难点，这将涉及到MFC的另一个重要技术---"执行期类型识别"。此项技术我将在MFC 技术内幕系列之（三）---《MFC执行期类型识别与动态创建技术内幕》中详细讲解。回到眼前来，源代码中这样作是为了将CMyDoc， CChildFrame，CMyView各类中的static CRuntimeClass class##class_name地址赋予CMultiDocTemplate类的各CRuntimeClass*指针成员m_pDocClass， m_pFrameClass和m_pViewClass，这位以后的动态创建Document/Frame/View"三口组"打下了基础。////* 3.文档模板列队 *////文 档模板初始化结束后，InitInstance函数调用了CWinApp::AddDocTemplate(pDocTemplate)函数，其主要目的 是将以初始化后的那个文档模板加入到文档模板链表中,并由CDocManager类对象进行管理。以下操作就是为了完成此工作。注释1: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcappui2.cppvoid CWinApp::AddDocTemplate(CDocTemplate* pTemplate)//将CMultiDocTemplate* pDocTemplate{ //传给pTemplateif (m_pDocManager == NULL)m_pDocManager = new CDocManager;m_pDocManager->AddDocTemplate(pTemplate);}注释2: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcdocmgr.cppCDocManager::CDocManager(){}//目前是一个空函数；void CDocManager::AddDocTemplate(CDocTemplate* pTemplate)//部分源代码{if (pTemplate == NULL){...//}else{ASSERT_VALID(pTemplate);ASSERT(m_templateList.Find(pTemplate, NULL) == NULL);// must not be in listpTemplate->LoadTemplate();m_templateList.AddTail(pTemplate);//CPtrList m_templateList is a member //of CDocManager}} ////* 4.创建程序主框架窗口 *////应用程序实例化了一个CMainFrame类对象，并调用LoadFrame函数加载窗口资源创建主框架窗口。以下是创建主框架窗口的流程。创 建窗口的主要代码是：pMainFrame->LoadFrame(IDR_MAINFRAME)；LoadFrame函数是MFC包装了窗口创建 过程的函数，在后面动态创建Child窗口时，它还将披挂上阵(但稍有不同）。下面是它的源代码,让我们仔细分析一下:注释1: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcwinmdi.cppBOOL CMDIFrameWnd::LoadFrame(UINT nIDResource, DWORD dwDefaultStyle,CWnd* pParentWnd, CCreateContext* pContext) {if (!CFrameWnd::LoadFrame(nIDResource, dwDefaultStyle,pParentWnd, pContext))return FALSE;// save menu to use when no active MDI child window is presentASSERT(m_hWnd != NULL);m_hMenuDefault = ::GetMenu(m_hWnd);if (m_hMenuDefault == NULL)TRACE(traceAppMsg, 0, "Warning: CMDIFrameWnd without a default menu.");return TRUE;}CMDIFrameWnd::LoadFrame调用了其基类CFrameWnd的LoadFrame，并将参数原封不动的传给它。注释2: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcwinfrm.cppBOOL CFrameWnd::LoadFrame(UINT nIDResource, DWORD dwDefaultStyle,CWnd* pParentWnd, CCreateContext* pContext) //部分源代码{...//CString strFullString;if (strFullString.LoadString(nIDResource))AfxExtractSubString(m_strTitle, strFullString, 0); // first sub-stringVERIFY(AfxDeferRegisterClass(AFX_WNDFRAMEORVIEW_REG));// attempt to create the windowLPCTSTR lpszClass = GetIconWndClass(dwDefaultStyle, nIDResource);CString strTitle = m_strTitle;if (!Create(lpszClass, strTitle, dwDefaultStyle, rectDefault,pParentWnd, MAKEINTRESOURCE(nIDResource), 0L, pContext)){return FALSE; // will self destruct on failure normally}...//if (pContext == NULL) // send initial updateSendMessageToDescendants(WM_INITIALUPDATE, 0, 0, TRUE, TRUE);return TRUE;}///* 4.1注册应用程序主框架窗口类 *///在 传统的Win32API编程中，创建窗口一般步骤是定义窗口类，注册窗口类，并调用::CreateWindow函数来创建。前面说过LoadFrame 函数封装了MFC创建窗口的过程，那么也就是说LoadFrame函数将负责定义窗口类，注册窗口类等琐碎工作。下面我们就通过挖掘源代码来看看 LoadFrame函数是如何完成这些工作的。LoadFrame首先调用AfxDeferRegisterClass(AFX_WNDFRAMEORVIEW_REG)，注释1: 以下宏定义在：..Visual Studio.NETvc7atlmfcsrcmfcafximpl.h#define AfxDeferRegisterClass(fClass) AfxEndDeferRegisterClass(fClass)注释2: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcwincore.cppBOOL AFXAPI AfxEndDeferRegisterClass(LONG fToRegister)//部分源代码{// mask off all classes that are already registeredAFX_MODULE_STATE* pModuleState = AfxGetModuleState();fToRegister &= ~pModuleState->m_fRegisteredClasses;if (fToRegister == 0)return TRUE;LONG fRegisteredClasses = 0;// common initializationWNDCLASS wndcls;memset(&wndcls, 0, sizeof(WNDCLASS)); // start with NULL defaultswndcls.lpfnWndProc = DefWindowProc;wndcls.hInstance = AfxGetInstanceHandle();wndcls.hCursor = afxData.hcurArrow;INITCOMMONCONTROLSEX init;init.dwSize = sizeof(init);// work to register classes as specified by fToRegister, populate fRegisteredClasses as we goif (fToRegister & AFX_WND_REG){// Child windows - no brush, no icon, safest default class styleswndcls.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;wndcls.lpszClassName = _afxWnd;if (AfxRegisterClass(&wndcls))fRegisteredClasses |= AFX_WND_REG;}...//if (fToRegister & AFX_WNDMDIFRAME_REG){// MDI Frame window (also used for splitter window)wndcls.style = CS_DBLCLKS;wndcls.hbrBackground = NULL;if (_AfxRegisterWithIcon(&wndcls, _afxWndMDIFrame, AFX_IDI_STD_MDIFRAME))fRegisteredClasses |= AFX_WNDMDIFRAME_REG;}if (fToRegister & AFX_WNDFRAMEORVIEW_REG){// SDI Frame or MDI Child windows or views - normal colorswndcls.style = CS_DBLCLKS | CS_HREDRAW | CS_VREDRAW;wndcls.hbrBackground = (HBRUSH) (COLOR_WINDOW + 1);if (_AfxRegisterWithIcon(&wndcls, _afxWndFrameOrView, AFX_IDI_STD_FRAME))fRegisteredClasses |= AFX_WNDFRAMEORVIEW_REG;} ...//// must have registered at least as mamy classes as requestedreturn (fToRegister & fRegisteredClasses) == fToRegister;}MFC预定义了若干个“窗口类模板”，比如"AFX_WNDMDIFRAME_REG","AFX_WNDFRAMEORVIEW_REG"等，MFC在LoadFrame 函数中调用AfxEndDeferRegisterClass函数为你的应用程序预注册了适当的窗口类。本例中预注册的窗口类为 AFX_WNDFRAMEORVIEW_REG。（注意是预注册，如果你在后面更改了CREATESTRUCT结构的域成员，MFC还会根据你的更改重新 为你的应用程序正式注册新的窗口类，稍候会有详细叙述）预注册完窗口类，MFC将判断你是否想更改窗口类的各参数。若你更改了，则MFC会重新注册新类；否则源预注册的窗口类就将成为正式的窗口类。下面我们来看看MFC的判断过程：此判断过程由GetIconWndClass开始LPCTSTR lpszClass = GetIconWndClass(dwDefaultStyle, nIDResource);注释3: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcwinfrm.cppLPCTSTR CFrameWnd::GetIconWndClass(DWORD dwDefaultStyle, UINT nIDResource)//部分源代码{...//HICON hIcon = ::LoadIcon(hInst, MAKEINTRESOURCE(nIDResource));if (hIcon != NULL){CREATESTRUCT cs;memset(&cs, 0, sizeof(CREATESTRUCT));cs.style = dwDefaultStyle;PreCreateWindow(cs);// will fill lpszClassName with default WNDCLASS name// ignore instance handle from PreCreateWindow.WNDCLASS wndcls;if (cs.lpszClass != NULL &&GetClassInfo(AfxGetInstanceHandle(), cs.lpszClass, &wndcls) &&wndcls.hIcon != hIcon){// register a very similar WNDCLASSreturn AfxRegisterWndClass(wndcls.style,wndcls.hCursor, wndcls.hbrBackground, hIcon);}}return NULL; // just use the default}GetIconWndClass 函数将调用CMainFrame::PreCreateWindow(CREATESTRUCT& cs)来看看应用程序是否修改了CREATESTRUCT结构的域成员。CMainFrame::PreCreateWindow调用 CMDIFrameWnd::PreCreateWindow(CREATESTRUCT& cs)，后者的代码如下:BOOL CMDIFrameWnd::PreCreateWindow(CREATESTRUCT& cs)//in winmdi.cpp{if (cs.lpszClass == NULL){VERIFY(AfxDeferRegisterClass(AFX_WNDMDIFRAME_REG));cs.lpszClass = _afxWndMDIFrame;}return TRUE;}MFC将为应用程序注册AFX_WNDMDIFRAME_REG预定义窗口类，并设置cs.lpszClass = _afxWndMDIFrame。在应用程序的代码中我更改了cs结构：BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs){if( !CMDIFrameWnd::PreCreateWindow(cs) )return FALSE;// TODO: 在此处通过修改 CREATESTRUCT cs 来修改窗口类或// 样式cs.dwExStyle=~WS_EX_CLIENTEDGE;return TRUE;} CMainFrame:: PreCreateWindow返回后，GetIconWndClass函数调用GetClassInfo函数重新收集cs信息（此时的信息已是更改后的 了)，并调用AfxRegisterWndClass函数重新注册该窗口类（此窗口类为该应用程序的正式窗口类）。到此为止窗口类注册完毕，以后程序还会 调用一次CMainFrame::PreCreateWindow，不过那此只是"过门不如"而已。//* 4.2主框架窗口创建开始 *//开始进入创建框架窗口的实质阶段。看LoadFrame函数做了什么?原来它调用了Create函数。注释1: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcwinfrm.cppBOOL CFrameWnd::Create(LPCTSTR lpszClassName,LPCTSTR lpszWindowName,DWORD dwStyle,const RECT& rect,CWnd* pParentWnd,LPCTSTR lpszMenuName,DWORD dwExStyle,CCreateContext* pContext){HMENU hMenu = NULL;if (lpszMenuName != NULL){// load in a menu that will get destroyed when window gets destroyedHINSTANCE hInst = AfxFindResourceHandle(lpszMenuName, RT_MENU);if ((hMenu = ::LoadMenu(hInst, lpszMenuName)) == NULL){TRACE(traceAppMsg, 0, "Warning: failed to load menu for CFrameWnd.");PostNcDestroy(); // perhaps delete the C++ objectreturn FALSE;}}m_strTitle = lpszWindowName; // save title for laterif (!CreateEx(dwExStyle, lpszClassName, lpszWindowName, dwStyle,rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top,pParentWnd->GetSafeHwnd(), hMenu, (LPVOID)pContext)){TRACE(traceAppMsg, 0, "Warning: failed to create CFrameWnd.");if (hMenu != NULL)DestroyMenu(hMenu);return FALSE;}return TRUE;}简单地说CFrameWnd::Create函数调用了基类的CWnd::CreateEx；注释2: 以下函数定义在：..Visual Studio.NETvc7atlmfcsrcmfcwincore.cppBOOL CWnd::CreateEx(DWORD dwExStyle, LPCTSTR lpszClassName,LPCTSTR lpszWindowName, DWORD dwStyle,int x, int y, int nWidth, int nHeight,HWND hWndParent, HMENU nIDorHMenu, LPVOID lpParam)//部分源代码{// allow modification of several common create parametersCREATESTRUCT cs;cs.dwExStyle = dwExStyle;cs.lpszClass = lpszClassName;cs.lpszName = lpszWindowName;cs.style = dwStyle;cs.x = x;cs.y = y;cs.cx = nWidth;cs.cy = nHeight;cs.hwndParent = hWndParent;cs.hMenu = nIDorHMenu;cs.hInstance = AfxGetInstanceHandle();cs.lpCreateParams = lpParam;if (!PreCreateWindow(cs)){PostNcDestroy();return FALSE;}AfxHookWindowCreate(this);HWND hWnd = ::CreateWindowEx(cs.dwExStyle, cs.lpszClass,cs.lpszName, cs.style, cs.x, cs.y, cs.cx, cs.cy,cs.hwndParent, cs.hMenu, cs.hInstance, cs.lpCreateParams);...//return TRUE;}BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs){if( !CMDIFrameWnd::PreCreateWindow(cs) )return FALSE;// TODO: 在此处通过修改 CREATESTRUCT cs 来修改窗口类或// 样式cs.dwExStyle=~WS_EX_CLIENTEDGE;return TRUE;}BOOL CMDIFrameWnd::PreCreateWindow(CREATESTRUCT& cs){if (cs.lpszClass == NULL){VERIFY(AfxDeferRegisterClass(AFX_WNDMDIFRAME_REG));cs.lpszClass = _afxWndMDIFrame;}return TRUE;}CWnd::CreateEx调用了CMainFrame::PreCreateWindow，但此次AfxDeferRegisterClass将不会被调用。也就是我上面所说的“过门不入”。CWnd::CreateEx函数还调用了AfxHookWindowCreate(this);后者是干什么的呢？其实它与消息映射和命令传递有关，我将在MFC技术内幕系列之（四）--《MFC消息映射与消息传递内幕》一文中详解。CWnd::CreateEx调用Win32API ::CreateWindowEx函数（传统的Win32API程序员一定不陌生这个函数），就这样主框架窗口创建结束。 ///* 5.标准外壳命令解析 *////MFC向导制作的标准MDI应用程序启动时，应用程序会自动启动一个子窗口框架（实际上是一套文档模板），这是为何呢？下面我将详细讲解一下这个创建过程.其实这一过程也是在CMyWinApp::InitInstance()函数中完成的，看看下面代码：CCommandLineInfo cmdInfo;ParseCommandLine(cmdInfo);if (!ProcessShellCommand(cmdInfo))return FALSE;函数首先实例化一个CCommandLineInfo类对象cmdInfo，让我们看看CCommandLineInfo是个什么东东? //in afxwin.hclass CCommandLineInfo : public CObject//部分源代码{public:// Sets default valuesCCommandLineInfo();...//BOOL m_bShowSplash;BOOL m_bRunEmbedded;BOOL m_bRunAutomated;enum { FileNew, FileOpen, FilePrint, FilePrintTo, FileDDE, AppRegister,AppUnregister, FileNothing = -1 } m_nShellCommand;// not valid for FileNewCString m_strFileName;// valid only for FilePrintToCString m_strPrinterName;CString m_strDriverName;CString m_strPortName;~CCommandLineInfo();// Implementation...//}; 再让我们来看看它的构造函数的实现：//in appcore.cppCCommandLineInfo::CCommandLineInfo(){m_bShowSplash = TRUE;m_bRunEmbedded = FALSE;m_bRunAutomated = FALSE;m_nShellCommand = FileNew;}m_nShellCommand = FileNew;这一句对我们最重要；至于CWinApp::ParseCommandLine我想用MFC文档中的一句话来解释：Call this member function to parse the command line and send the parameters, one at a time, to CCommandLineInfo::ParseParam.下面我们来看看外壳命令解析的主角：CWinApp::ProcessShellCommand//in appui2.cpp //DDE and ShellExecute supportBOOL CWinApp::ProcessShellCommand(CCommandLineInfo& rCmdInfo)//部分源代码{BOOL bResult = TRUE;switch (rCmdInfo.m_nShellCommand){case CCommandLineInfo::FileNew:if (!AfxGetApp()->OnCmdMsg(ID_FILE_NEW, 0, NULL, NULL))OnFileNew();if (m_pMainWnd == NULL)bResult = FALSE;break;// If we've been asked to open a file, call OpenDocumentFile()case CCommandLineInfo::FileOpen:if (!OpenDocumentFile(rCmdInfo.m_strFileName))bResult = FALSE;break;case CCommandLineInfo::FilePrintTo:case CCommandLineInfo::FilePrint:...//case CCommandLineInfo::FileDDE:...//case CCommandLineInfo::AppRegister:...//case CCommandLineInfo::AppUnregister:...//}return bResult;}挖 掘源代码的确是了解MFC运行内幕的最好手段，大家一看源代码便知道如之何了。CCommandLineInfo构造函数中 m_nShellCommand = FileNew;所以在ProcessShellCommand中对应的代码自然就一目了然了：CWinApp::OnFileNew()被调用了。///* 6.一套文档/视图即将诞生 *///上文说CWinApp::OnFileNew()被调用了，那么就让我来看看其代码吧！//in appdlg.cppvoid CWinApp::OnFileNew(){if (m_pDocManager != NULL)m_pDocManager->OnFileNew();}//in docmgr.cppvoid CDocManager::OnFileNew()//部分源代码{...//CDocTemplate* pTemplate = (CDocTemplate*)m_templateList.GetHead();if (m_templateList.GetCount() > 1){// more than one document template to choose from// bring up dialog prompting userCNewTypeDlg dlg(&m_templateList);INT_PTR nID = dlg.DoModal();if (nID == IDOK)pTemplate = dlg.m_pSelectedTemplate;elsereturn; // none - cancel operation}ASSERT(pTemplate != NULL);ASSERT_KINDOF(CDocTemplate, pTemplate);pTemplate->OpenDocumentFile(NULL);// if returns NULL, the user has already been alerted}//in docmulti.cppCDocument* CMultiDocTemplate::OpenDocumentFile(LPCTSTR lpszPathName,BOOL bMakeVisible)//部分源代码{CDocument* pDocument = CreateNewDocument();...//BOOL bAutoDelete = pDocument->m_bAutoDelete;pDocument->m_bAutoDelete = FALSE; // don't destroy if something goes wrongCFrameWnd* pFrame = CreateNewFrame(pDocument, NULL);pDocument->m_bAutoDelete = bAutoDelete;...//if (lpszPathName == NULL){// create a new document - with default document nameSetDefaultTitle(pDocument);// avoid creating temporary compound file when starting up invisibleif (!bMakeVisible)pDocument->m_bEmbedded = TRUE;if (!pDocument->OnNewDocument()){// user has be alerted to what failed in OnNewDocumentTRACE(traceAppMsg, 0, "CDocument::OnNewDocument returned FALSE.");pFrame->DestroyWindow();return NULL;}// it worked, now bump untitled countm_nUntitledCount++;}else{// open an existing documentCWaitCursor wait;if (!pDocument->OnOpenDocument(lpszPathName)){// user has be alerted to what failed in OnOpenDocumentTRACE(traceAppMsg, 0, "CDocument::OnOpenDocument returned FALSE.");pFrame->DestroyWindow();return NULL;}pDocument->SetPathName(lpszPathName);}InitialUpdateFrame(pFrame, pDocument, bMakeVisible);return pDocument;}///* 6.1.子文档动态生成 *///CMultiDocTemplate::OpenDocumentFile调用了CreateNewDocument()，这就是子文档动态生成的主函数。//in doctempl.cppCDocument* CDocTemplate::CreateNewDocument()//部分源代码{// default implementation constructs one from CRuntimeClass...//CDocument* pDocument = (CDocument*)m_pDocClass->CreateObject();...//AddDocument(pDocument);//将动态生成的文档对象的指针加入到应用程序的文档列表中return pDocument;}CDocument* pDocument = (CDocument*)m_pDocClass->CreateObject()；这一句就是动态产生的核心，它借助于 CRuntimeClass动态生成一个CDocument对象。其动态生成的奥秘我将在MFC技术内幕系列之（三）---《MFC执行期类型识别与动态创建技术内幕》一文中详解。///* 6.2.子窗口框架动态生成 *//CMultiDocTemplate::OpenDocumentFile调用了CreateNewFrame，这就是子窗口框架动态生成的主函数。// Default frame creationCFrameWnd* CDocTemplate::CreateNewFrame(CDocument* pDoc, CFrameWnd* pOther)//部分源代码{if (pDoc != NULL)ASSERT_VALID(pDoc);// create a frame wired to the specified documentASSERT(m_nIDResource != 0); // must have a resource ID to load fromCCreateContext context;context.m_pCurrentFrame = pOther;context.m_pCurrentDoc = pDoc;context.m_pNewViewClass = m_pViewClass;context.m_pNewDocTemplate = this;...//CFrameWnd* pFrame = (CFrameWnd*)m_pFrameClass->CreateObject();if (pFrame == NULL){TRACE(traceAppMsg, 0, "Warning: Dynamic create of frame %hs failed.",m_pFrameClass->m_lpszClassName);return NULL;}ASSERT_KINDOF(CFrameWnd, pFrame);...//// create new from resourceif (!pFrame->LoadFrame(m_nIDResource,WS_OVERLAPPEDWINDOW | FWS_ADDTOTITLE, // default frame stylesNULL, &context)){TRACE(traceAppMsg, 0, "Warning: CDocTemplate couldn't create a frame.");// frame will be deleted in PostNcDestroy cleanupreturn NULL;}// it worked !return pFrame;}CFrameWnd* pFrame = (CFrameWnd*)m_pFrameClass->CreateObject();这一句就是动态产生的核心，它借助于 CRuntimeClass动态生成一个CDocument对象。其动态生成的奥秘我将在MFC技术内幕系列之（三）---《MFC执行期类型识别与动态创建技术内幕》一文中详解。之后函数调用LoadFrame来创建子窗口。其过程与创建主框架窗口的过程大致相同，但也有一些不同的地方，下面我就将说说这点不同。///* 6.3.子视图动态生成 *///瞪大眼睛仔细察看OpenDocumentFile的源代码，疑惑了,"怎么没有类似CView* pView =CreateNewView();的代码?","那么子视图是如何生成的呢"下面我就为你详细解释一下吧！其实子视图动态生成函数被放到另一个地方了。让我们详细来看看吧。其实，关键还是在LoadFrame，但与创建主窗口框架的那个LoadFrame不同的是传进了一个不同的参数&context，你回过头看看主窗口框架的那个LoadFrame，调用它时使用了默认参数，而那个默认参数值为NULL,下面看看CCreateContext 结构。//in afxext.hstruct CCreateContext // Creation information structure// All fields are optional and may be NULL{// for creating new viewsCRuntimeClass* m_pNewViewClass; // runtime class of view to create or NULLCDocument* m_pCurrentDoc;// for creating MDI children (CMDIChildWnd::LoadFrame)CDocTemplate* m_pNewDocTemplate;// for sharing view/frame state from the original view/frameCView* m_pLastView;CFrameWnd* m_pCurrentFrame;// ImplementationCCreateContext();};而在CDocTemplate::CreateNewFrame中初始化了该结构如下：CCreateContext context;context.m_pCurrentFrame = pOther;context.m_pCurrentDoc = pDoc;context.m_pNewViewClass = m_pViewClass;context.m_pNewDocTemplate = this;context.m_pNewViewClass = m_pViewClass;//关键的成员下面看看这个创建的具体过程：LoadFrame(...,&context)-->CFrameWnd::Create(...,&context)--> CWnd::CreateEx(...,&context)-->::CreateWindowEx::CreateWindowEx API函数将产生WM_CREATE消息，并将&context传递之,CMainFrame::OnCreate将响应消息,并引起一系列的函数调用，看下面://in mainfrm.cppint CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct){if (CMDIFrameWnd::OnCreate(lpCreateStruct) == -1)return -1;...//return 0;}// in winfrm.cppint CFrameWnd::OnCreate(LPCREATESTRUCT lpcs){CCreateContext* pContext = (CCreateContext*)lpcs->lpCreateParams;return OnCreateHelper(lpcs, pContext);}// in winfrm.cppint CFrameWnd::OnCreateHelper(LPCREATESTRUCT lpcs, CCreateContext* pContext)//部分源代码{if (CWnd::OnCreate(lpcs) == -1)return -1;// create special children firstif (!OnCreateClient(lpcs, pContext)){TRACE(traceAppMsg, 0, "Failed to create client pane/view for frame.");return -1;}...//return 0; // create ok}// in winfrm.cppBOOL CFrameWnd::OnCreateClient(LPCREATESTRUCT, CCreateContext* pContext){// default create client will create a view if asked for itif (pContext != NULL && pContext->m_pNewViewClass != NULL){if (CreateView(pContext, AFX_IDW_PANE_FIRST) == NULL)return FALSE;}return TRUE;}// in winfrm.cppCWnd* CFrameWnd::CreateView(CCreateContext* pContext, UINT nID)//部分源代码{...//// Note: can be a CWnd with PostNcDestroy self cleanupCWnd* pView = (CWnd*)pContext->m_pNewViewClass->CreateObject();if (pView == NULL){TRACE(traceAppMsg, 0, "Warning: Dynamic create of view type %hs failed.",pContext->m_pNewViewClass->m_lpszClassName);return NULL;}ASSERT_KINDOF(CWnd, pView);// views are always created with a border!if (!pView->Create(NULL, NULL, AFX_WS_DEFAULT_VIEW,CRect(0,0,0,0), this, nID, pContext)){TRACE(traceAppMsg, 0, "Warning: could not create view for frame.");return NULL; // can't continue without a view}...//return pView;}CWnd* pView = (CWnd*)pContext->m_pNewViewClass->CreateObject();核心函数终于出现了。子视图动态生成完毕。//* 7.收尾工作 *//至 此，一套完整的Document/ChildFrame/View结构生成,此“三口组”共属同一套文档模板，如果你要定义另一套不同的文档模档需再定义 另一组不同“三口组”（ChildFrame可以使用相同的）。并调用AddDocTemplate将该文档模板加入到应用程序的文档模板列表。比如：CMultiDocTemplate* pOtherDocTemplate;pOtherDocTemplate = new CMultiDocTemplate(IDR_MyOtherTYPE,RUNTIME_CLASS(CMyOtherDoc),RUNTIME_CLASS(CChildFrame), // 自定义 MDI 子框架RUNTIME_CLASS(CMyOtherView));AddDocTemplate(pOtherDocTemplate);“三口组”生成后程序调用ShowWindow，UpdateWindow将应用程序的主窗口展现在你眼前。注释:当你在File菜单中选择new或在工具栏中单击“新建”时，应用程序将选择当前默认的文档模板并以它为基础动态生成 Document/ChildFrame/View“三口组”，其生成过程与我上述讲的一般不二。