建立空文档失败

 这类问题的出现主要在bool CWinApp::ProcessShellCommand(CCommandLineInfo& rCmdInfo);

函数的内容如下(在C:\Program Files\Microsoft Visual Studio 8\VC\atlmfc\src\mfc\appui2.cpp)

BOOL CWinApp::ProcessShellCommand(CCommandLineInfo& rCmdInfo)
{
	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;

		// If the user wanted to print, hide our main window and
		// fire a message to ourselves to start the printing

	case CCommandLineInfo::FilePrintTo:
	case CCommandLineInfo::FilePrint:
		m_nCmdShow = SW_HIDE;
		ASSERT(m_pCmdInfo == NULL);
		if(OpenDocumentFile(rCmdInfo.m_strFileName))
		{
			m_pCmdInfo = &rCmdInfo;
			ENSURE_VALID(m_pMainWnd);
			m_pMainWnd->SendMessage(WM_COMMAND, ID_FILE_PRINT_DIRECT);
			m_pCmdInfo = NULL;
		}
		bResult = FALSE;
		break;

		// If we're doing DDE, hide ourselves

	case CCommandLineInfo::FileDDE:
		m_pCmdInfo = (CCommandLineInfo*)(UINT_PTR)m_nCmdShow;
		m_nCmdShow = SW_HIDE;
		break;

	// If we've been asked to register, exit without showing UI.
	// Registration was already done in InitInstance().
	case CCommandLineInfo::AppRegister:
		{
			Register();			
			bResult = FALSE;    // that's all we do

			// If nobody is using it already, we can use it.
			// We'll flag that we're unregistering and not save our state
			// on the way out. This new object gets deleted by the
			// app object destructor.

			if (m_pCmdInfo == NULL)
			{
				m_pCmdInfo = new CCommandLineInfo;
				m_pCmdInfo->m_nShellCommand = CCommandLineInfo::AppUnregister;
			}
			break;
		}

	// If we've been asked to unregister, unregister and then terminate
	case CCommandLineInfo::AppUnregister:
		{
			BOOL bUnregistered = Unregister();

			// if you specify /EMBEDDED, we won't make an success/failure box
			// this use of /EMBEDDED is not related to OLE

			if (!rCmdInfo.m_bRunEmbedded)
			{
				if (bUnregistered)
					AfxMessageBox(AFX_IDP_UNREG_DONE);
				else
					AfxMessageBox(AFX_IDP_UNREG_FAILURE);
			}
			bResult = FALSE;    // that's all we do

			// If nobody is using it already, we can use it.
			// We'll flag that we're unregistering and not save our state
			// on the way out. This new object gets deleted by the
			// app object destructor.

			if (m_pCmdInfo == NULL)
			{
				m_pCmdInfo = new CCommandLineInfo;
				m_pCmdInfo->m_nShellCommand = CCommandLineInfo::AppUnregister;
			}
		}
		break;
	}
	return bResult;
}

通过上面的内容我们可以看出：如果没有对ID_FILE_NEW做映射的话出现问题就在OnFileNew();   CWinApp对OnFileNew的默认实现是调用m_pDocManager->OnFileNew();我们继续解析cdocmanager，它究竟干了些什么？   （首先说明一下CDocManager它主要的功能是帮助CWinApp是管理文档模板链表和注册文件类型.）

//如果模板列表为空的话   

if (m_templateList.IsEmpty())   

{   

 TRACE0("Error: no document templates registered with CWinApp.");   

 AfxMessageBox(AFX_IDP_FAILED_TO_CREATE_DOC);  //报错并返回.这里不会报建立新文档出错。  

 return; 

}

cdoctemplate* pTemplate = (CDocTemplate*)m_templateList.GetHead();   

if (m_templateList.GetCount() > 1)   

{   

 // more than one document template to choose from   

 // bring up dialog prompting user  

 CNewTypeDlg dlg(&m_templateList);   

 int nID = dlg.DoModal();   

 if (nID == IDOK)   

  pTemplate = dlg.m_pSelectedTemplate;  

 else 

  return;     // none - cancel operation   

}

assert(ptemplate != NULL);   

ASSERT_KINDOF(CDocTemplate， pTemplate);

ptemplate->opendocumentfile(null);
 

过观察上面的代码我们很容易的看出 有两个可能出错的原因：1 CreateNewDocument返回为NULL 2 createnewframe 返回为空。先看 CreateNewDocument() 一般来说这个函数很少失败。不过在调试时也不能掉以轻心。  再看看CreateNewFrame()  里面有一个函数LoadFrame是造成这种“建立新文档失败”错误的源泉所在。   只要它返回False就会弹出这样的提示。   我们在来看看LoadFrame() 里面调用CFrameWnd::Create()来创建窗口，创建窗口失败返回Fasle。  这样问题就变的比较简单了。看看create和createex函数的动作就知道怎么回事了。   

1 如果找不到菜单资源 返回False 同时也弹出“建立空文档失败”  

2 重载了PreCreateWindow而且返回False也会导致弹出“建立空文档失败” 

3 在OnCreate 里面返回-1 也会导致弹出“建立空文档失败”。