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MFC多文档程序，从菜单关闭一个文档和直接点击右上角的x效果不同

news 来源：原创 2025/4/23 9:54:20

MFC多文档程序，从菜单关闭一个文档和直接点击右上角的x效果不同

若文档内容有修改，则前者会询问用户，是否保存修改；后者不保存修改直接关闭。
原因在于，从菜单关闭时，调用OnClose，一定会调用SaveModified()，其源码如下

/
// Standard file menu commands

void CDocument::OnFileClose()
{
	if (!SaveModified())
		return;

	// shut it down
	OnCloseDocument();
		// this should destroy the document
}

而点击x关闭时，CanCloseFrame()函数会判断是否保存文档，其源码如下：

BOOL CDocument::CanCloseFrame(CFrameWnd* pFrameArg)
	// permission to close all views using this frame
	//  (at least one of our views must be in this frame)
{
	ASSERT_VALID(pFrameArg);
	UNUSED(pFrameArg);   // unused in release builds

	POSITION pos = GetFirstViewPosition();
	while (pos != NULL)
	{
		CView* pView = GetNextView(pos);
		ASSERT_VALID(pView);
		CFrameWnd* pFrame = pView->GetParentFrame();
		// assume frameless views are ok to close
		if (pFrame != NULL)
		{
			// assumes 1 document per frame
			ASSERT_VALID(pFrame);
			if (pFrame->m_nWindow > 0)
				return TRUE;        // more than one frame refering to us
		}
	}

	// otherwise only one frame that we know about
	return SaveModified();
}

可见，仅当父框架的窗口为0时才会执行SaveModified()语句，其余情况都只会返回TRUE。在使用多文档编程时，要注意为了文档的安全，在自己重载的CanCloseFrame()中加上SaveModified()语句。

如何默默保存，不询问用户？

CDocument::SaveModified()的实现如下：

BOOL CDocument::SaveModified()
{
	if (!IsModified())
		return TRUE;        // ok to continue

	// get name/title of document
	CString name;
	if (m_strPathName.IsEmpty())
	{
		// get name based on caption
		name = m_strTitle;
		if (name.IsEmpty())
			VERIFY(name.LoadString(AFX_IDS_UNTITLED));
	}
	else
	{
		// get name based on file title of path name
		name = m_strPathName;
		if (afxData.bMarked4)
		{
			AfxGetFileTitle(m_strPathName, name.GetBuffer(_MAX_PATH), _MAX_PATH);
			name.ReleaseBuffer();
		}
	}

	CString prompt;
	AfxFormatString1(prompt, AFX_IDP_ASK_TO_SAVE, name);
	switch (AfxMessageBox(prompt, MB_YESNOCANCEL, AFX_IDP_ASK_TO_SAVE))
	{
	case IDCANCEL:
		return FALSE;       // don't continue

	case IDYES:
		// If so, either Save or Update, as appropriate
		if (!DoFileSave())
			return FALSE;       // don't continue
		break;

	case IDNO:
		// If not saving changes, revert the document
		break;

	default:
		ASSERT(FALSE);
		break;
	}
	return TRUE;    // keep going
}