MFC 建立新文檔失敗 - 緣由之一

// 我在建立新文檔時一般經過pDocTemplate->OpenDocumentFile(NULL)的方式建立；
// 下面貼出調用代碼
// AFX_IDP_FAILED_TO_CREATE_DOC就是「建立空文檔失敗」
// 當前遇到的狀況是在CFrameWnd* pFrame = CreateNewFrame(pDocument, NULL);
// 建立框架窗口時失敗，進行跟就去

CDocument* CMultiDocTemplate::OpenDocumentFile(LPCTSTR lpszPathName, BOOL bMakeVisible)
{
	return OpenDocumentFile(lpszPathName, TRUE, bMakeVisible);
}

CDocument* CMultiDocTemplate::OpenDocumentFile(LPCTSTR lpszPathName, BOOL bAddToMRU, BOOL bMakeVisible)
{
	CDocument* pDocument = CreateNewDocument();
	if (pDocument == NULL)
	{
		TRACE(traceAppMsg, 0, "CDocTemplate::CreateNewDocument returned NULL.\n");
		AfxMessageBox(AFX_IDP_FAILED_TO_CREATE_DOC);
		return NULL;
	}
	ASSERT_VALID(pDocument);

	BOOL bAutoDelete = pDocument->m_bAutoDelete;
	pDocument->m_bAutoDelete = FALSE;   // don't destroy if something goes wrong
	CFrameWnd* pFrame = CreateNewFrame(pDocument, NULL);
	pDocument->m_bAutoDelete = bAutoDelete;
	if (pFrame == NULL)
	{
		AfxMessageBox(AFX_IDP_FAILED_TO_CREATE_DOC);
		delete pDocument;       // explicit delete on error
		return NULL;
	}
	ASSERT_VALID(pFrame);

	if (lpszPathName == NULL)
	{
		// create a new document - with default document name
		SetDefaultTitle(pDocument);

		// avoid creating temporary compound file when starting up invisible
		if (!bMakeVisible)
			pDocument->m_bEmbedded = TRUE;

		if (!pDocument->OnNewDocument())
		{
			// user has be alerted to what failed in OnNewDocument
			TRACE(traceAppMsg, 0, "CDocument::OnNewDocument returned FALSE.\n");
			pFrame->DestroyWindow();
			return NULL;
		}

		// it worked, now bump untitled count
		m_nUntitledCount++;
	}
	else
	{
		// open an existing document
		CWaitCursor wait;
		if (!pDocument->OnOpenDocument(lpszPathName))
		{
			// user has be alerted to what failed in OnOpenDocument
			TRACE(traceAppMsg, 0, "CDocument::OnOpenDocument returned FALSE.\n");
			pFrame->DestroyWindow();
			return NULL;
		}
		pDocument->SetPathName(lpszPathName, bAddToMRU);
		pDocument->OnDocumentEvent(CDocument::onAfterOpenDocument);
	}

	InitialUpdateFrame(pFrame, pDocument, bMakeVisible);
	return pDocument;
}

// 更進去以後發現，CFrameWnd* pFrame = (CFrameWnd*)m_pFrameClass->CreateObject();
// 進行建立框架窗口，繼續跟進去

CFrameWnd* CDocTemplate::CreateNewFrame(CDocument* pDoc, CFrameWnd* pOther)
{
	if (pDoc != NULL)
		ASSERT_VALID(pDoc);
	// create a frame wired to the specified document

	ASSERT(m_nIDResource != 0); // must have a resource ID to load from
	CCreateContext context;
	context.m_pCurrentFrame = pOther;
	context.m_pCurrentDoc = pDoc;
	context.m_pNewViewClass = m_pViewClass;
	context.m_pNewDocTemplate = this;

	if (m_pFrameClass == NULL)
	{
		TRACE(traceAppMsg, 0, "Error: you must override CDocTemplate::CreateNewFrame.\n");
		ASSERT(FALSE);
		return NULL;
	}
	CFrameWnd* pFrame = (CFrameWnd*)m_pFrameClass->CreateObject();
	if (pFrame == NULL)
	{
		TRACE(traceAppMsg, 0, "Warning: Dynamic create of frame %hs failed.\n",
			m_pFrameClass->m_lpszClassName);
		return NULL;
	}
	ASSERT_KINDOF(CFrameWnd, pFrame);

	if (context.m_pNewViewClass == NULL)
		TRACE(traceAppMsg, 0, "Warning: creating frame with no default view.\n");

	// create new from resource
	if (!pFrame->LoadFrame(m_nIDResource,
			WS_OVERLAPPEDWINDOW | FWS_ADDTOTITLE,   // default frame styles
			NULL, &context))
	{
		TRACE(traceAppMsg, 0, "Warning: CDocTemplate couldn't create a frame.\n");
		// frame will be deleted in PostNcDestroy cleanup
		return NULL;
	}

	// it worked !
	return pFrame;
}

// 跟到這裏發現了緣由m_pfnCreateObject的值爲空
// DECLARE_DYNCREATE發現了這個宏
// 猜想跟建立子框架窗口的類時添加的宏有關
// 發現我本身建立子框架添加的宏是DECLARE_DYNAMIC
// 將修改成DECLARE_DYNCREATE便可成功
// 在.cpp文件中修改IMPLEMENT_DYNCREATE宏
// 出現這樣的緣由是經過嚮導建立默認添加的是DECLARE_DYNAMIC宏

CObject* CRuntimeClass::CreateObject()
{
	ENSURE(this);

	if (m_pfnCreateObject == NULL)
	{
		TRACE(traceAppMsg, 0,
			_T("Error: Trying to create object which is not ")
			_T("DECLARE_DYNCREATE \nor DECLARE_SERIAL: %hs.\n"),
			m_lpszClassName);
		return NULL;
	}

	CObject* pObject = NULL;
	TRY
	{
		pObject = (*m_pfnCreateObject)();
	}
	END_TRY

	return pObject;
}

// 下面給出這些宏定義的區別
#define DECLARE_DYNAMIC(class_name) \
public: \
	static const CRuntimeClass class##class_name; \
	virtual CRuntimeClass* GetRuntimeClass() const; \

#define _DECLARE_DYNAMIC(class_name) \
public: \
	static CRuntimeClass class##class_name; \
	virtual CRuntimeClass* GetRuntimeClass() const; \

#endif

// not serializable, but dynamically constructable
#define DECLARE_DYNCREATE(class_name) \
	DECLARE_DYNAMIC(class_name) \
	static CObject* PASCAL CreateObject();

#define _DECLARE_DYNCREATE(class_name) \
	_DECLARE_DYNAMIC(class_name) \
	static CObject* PASCAL CreateObject();


// 這只是我找到的緣由之一，調試了好久都沒找到緣由。
// 由於我發現問題的項目調試時沒法進到OpenDocumentFile中。
// 因此另建立了一個測試項目進行調試，才能夠跟就去。