在多文档下，可以通过在string table添加另外的字符串增加文件类型，如 IDR_MDITYPE：/n图像/n新建图像/n图像文件(*.aaa;*.bbb)/n.aaa;.bbb/nMDI.Document/nMDI.Document IDR_OtherTYPE：/n文本/n新建文本/n文本文件(*.ccc;*.ddd)/n.ccc;.ddd/nMDI.Document/nMDI.Document 这时，弹出的打开与保存对话框就可以选择相应的文件类型。 但是在单文档情况下，这种办法就不可取了。因为在单文档下，通常只有一个字符串资源和菜单IDR_MAINFRAME，当我们添加IDR_OtherTYPE的字符串资源时，就必须增加相应的菜单资源，这种作法似乎不是MFC的初衷。如画图等程序只有一个菜单，在新建时不会弹出文件类型选择提示框（不同与多文档），而打开和保存时却能选择多种文件类型。要是通过添加字符串来增加文件类型，虽然在打开和保存时能选择多种文件类型，但是新建时会弹出文件类型选择提示框，而且在一个文档打开的情况下，若新建或打开另一类型的文档，不会提示保存当前文档，而是直接在新的窗口打开。这显然与单文档的“定义”不符。为此，此处通过修改CDocManager::DoPromptFileName()来达到打开与保存多种文件类型的目的。工程名为SDI。 首先考虑打开对话框。第一步是要弄清，打开对话框是什么时候（在哪）弹出来的？ 默认情况下，CSDIApp调用CWinApp::OnFileOpen方法处理FileOpen事件： ON_COMMAND(ID_FILE_OPEN, &CWinApp::OnFileOpen) CWinApp::OnFileOpen又调用CDocManager::OnFileOpen处理FileOpen事件： void CWinApp::OnFileOpen() { ENSURE(m_pDocManager != NULL); m_pDocManager->OnFileOpen(); } CDocManager::OnFileOpen显示对话框与用户交互，然后调用CWinApp::OpenDocumentFile方法： void CDocManager::OnFileOpen() { // prompt the user (with all document templates) CString newName; if (!DoPromptFileName(newName, AFX_IDS_OPENFILE, OFN_HIDEREADONLY | OFN_FILEMUSTEXIST, TRUE, NULL)) return; // open cancelled
AfxGetApp()->OpenDocumentFile(newName); // if returns NULL, the user has already been alerted } 显然，一种可能的解决办法是绕过CWinApp和CDocManager，在CSDIApp::OnFileOpen方法中显示自定义对话框，然后调用CWinApp::OpenDocumentFile方法。 ON_COMMAND(ID_FILE_OPEN, &CSDIApp::OnFileOpen) void CSDIApp::OnFileOpen() { LPCTSTR szFilter = L"图像文件(*.aaa;*.bbb)|*.aaa;*.bbb|文本文件(*.ccc;*.ddd)|*.ccc;*.ddd||"; CFileDialog oFileDlg(TRUE, NULL, NULL, 4|2, szFilter);
if(oFileDlg.DoModal() == IDOK) OpenDocumentFile(oFileDlg.GetFileName()); // CSDIApp不需要重写CWinApp::OpenDocumentFile方法 } 现在考虑保存对话框。第一步仍然是弄清，保存对话框是什么时候（在哪）弹出来的？ 分发消息时，调用了CDocument::DoFileSave虚方法： BOOL CDocument::DoFileSave() { DWORD dwAttrib = GetFileAttributes(m_strPathName); if (dwAttrib & FILE_ATTRIBUTE_READONLY) { // we do not have read-write access or the file does not (now) exist if (!DoSave(NULL)) { TRACE(traceAppMsg, 0, "Warning: File save with new name failed./n"); return FALSE; } } else { if (!DoSave(m_strPathName)) { TRACE(traceAppMsg, 0, "Warning: File save failed./n"); return FALSE; } } return TRUE; } CDocument::DoFileSave调用CDocument::DoSave，也是一个虚方法：（注：没有DoSaveAs方法，lpszPathName参数决定了CDocument::DoSave是表现为“保存”还是“另存为”。） BOOL CDocument::DoSave(LPCTSTR lpszPathName, BOOL bReplace /*= TRUE*/) // Save the document data to a file // lpszPathName = path name where to save document file // if lpszPathName is NULL then the user will be prompted (SaveAs) // note: lpszPathName can be different than 'm_strPathName' // if 'bReplace' is TRUE will change file name if successful (SaveAs) // if 'bReplace' is FALSE will not change path name (SaveCopyAs) { CString newName = lpszPathName; if (newName.IsEmpty()) { CDocTemplate* pTemplate = GetDocTemplate(); ASSERT(pTemplate != NULL);
newName = m_strPathName; if (bReplace && newName.IsEmpty()) { newName = m_strTitle; // check for dubious filename int iBad = newName.FindOneOf(_T(":///")); if (iBad != -1) newName.ReleaseBuffer(iBad);
// append the default suffix if there is one CString strExt; if (pTemplate->GetDocString(strExt, CDocTemplate::filterExt) && !strExt.IsEmpty()) { ASSERT(strExt[0] == '.'); int iStart = 0; newName += strExt.Tokenize(_T(";"), iStart); } }
if (!AfxGetApp()->DoPromptFileName(newName, bReplace ? AFX_IDS_SAVEFILE : AFX_IDS_SAVEFILECOPY, OFN_HIDEREADONLY | OFN_PATHMUSTEXIST, FALSE, pTemplate)) return FALSE; // don't even attempt to save }
CWaitCursor wait;
if (!OnSaveDocument(newName)) { if (lpszPathName == NULL) { // be sure to delete the file TRY { CFile::Remove(newName); } CATCH_ALL(e) { TRACE(traceAppMsg, 0, "Warning: failed to delete file after failed SaveAs./n"); DELETE_EXCEPTION(e); } END_CATCH_ALL } return FALSE; }
// reset the title and change the document name if (bReplace) SetPathName(newName);
return TRUE; // success } CDocument::DoSave虚方法调用CWinApp::DoPromptFileName方法弹出保存对话框，后者又调用CDocManager::DoPromptFileName虚方法（情形与打开文件时相同）： BOOL CDocManager::DoPromptFileName(CString& fileName, UINT nIDSTitle, DWORD lFlags, BOOL bOpenFileDialog, CDocTemplate* pTemplate) { CFileDialog dlgFile(bOpenFileDialog, NULL, NULL, OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT, NULL, NULL, 0);
CString title; VERIFY(title.LoadString(nIDSTitle));
dlgFile.m_ofn.Flags |= lFlags;
CString strFilter; CString strDefault; if (pTemplate != NULL) { ASSERT_VALID(pTemplate); _AfxAppendFilterSuffix(strFilter, dlgFile.m_ofn, pTemplate, &strDefault); } else { // do for all doc template POSITION pos = m_templateList.GetHeadPosition(); BOOL bFirst = TRUE; while (pos != NULL) { pTemplate = (CDocTemplate*)m_templateList.GetNext(pos); _AfxAppendFilterSuffix(strFilter, dlgFile.m_ofn, pTemplate, bFirst ? &strDefault : NULL); bFirst = FALSE; } }
// append the "*.*" all files filter CString allFilter; VERIFY(allFilter.LoadString(AFX_IDS_ALLFILTER)); strFilter += allFilter; strFilter += (TCHAR)'/0'; // next string please strFilter += _T("*.*"); strFilter += (TCHAR)'/0'; // last string dlgFile.m_ofn.nMaxCustFilter++;
dlgFile.m_ofn.lpstrFilter = strFilter; dlgFile.m_ofn.lpstrTitle = title; dlgFile.m_ofn.lpstrFile = fileName.GetBuffer(_MAX_PATH);
INT_PTR nResult = dlgFile.DoModal(); fileName.ReleaseBuffer(); return nResult == IDOK; } AFX_STATIC void AFXAPI _AfxAppendFilterSuffix(CString& filter, OPENFILENAME& ofn, CDocTemplate* pTemplate, CString* pstrDefaultExt) { ENSURE_VALID(pTemplate); ASSERT_KINDOF(CDocTemplate, pTemplate); CString strFilterExt, strFilterName; if (pTemplate->GetDocString(strFilterExt, CDocTemplate::filterExt) && !strFilterExt.IsEmpty() && pTemplate->GetDocString(strFilterName, CDocTemplate::filterName) && !strFilterName.IsEmpty()) { if (pstrDefaultExt != NULL) pstrDefaultExt->Empty(); // add to filter filter += strFilterName; ASSERT(!filter.IsEmpty()); // must have a file type name filter += (TCHAR)'/0'; // next string please int iStart = 0; do { CString strExtension = strFilterExt.Tokenize( _T( ";" ), iStart ); if (iStart != -1) { // a file based document template - add to filter list // If you hit the following ASSERT, your document template // string is formatted incorrectly. The section of your // document template string that specifies the allowable file // extensions should be formatted as follows: // .<ext1>;.<ext2>;.<ext3> // Extensions may contain wildcards (e.g. '?', '*'), but must // begin with a '.' and be separated from one another by a ';'. // Example: // .jpg;.jpeg ASSERT(strExtension[0] == '.'); if ((pstrDefaultExt != NULL) && pstrDefaultExt->IsEmpty()) { // set the default extension *pstrDefaultExt = strExtension.Mid( 1 ); // skip the '.' ofn.lpstrDefExt = const_cast< LPTSTR >((LPCTSTR)(*pstrDefaultExt)); ofn.nFilterIndex = ofn.nMaxCustFilter + 1; // 1 based number } filter += (TCHAR)'*'; filter += strExtension; filter += (TCHAR)';'; // Always append a ';'. The last ';' will get replaced with a '/0' later. } } while (iStart != -1); filter.SetAt( filter.GetLength()-1, '/0' );; // Replace the last ';' with a '/0' ofn.nMaxCustFilter++; } } 看起来，重写CDocManager::DoPromptFileName方法比重写CDocument::DoSave方法要省事些： BOOL CSDIDocMgr::DoPromptFileName(CString& fileName, UINT nIDSTitle, DWORD lFlags, BOOL bOpenFileDialog, CDocTemplate* pTemplate) { LPCTSTR strFilter = L"图像文件(*.aaa)/0*.aaa/0文本文件 (*.bbb)/0*.bbb/0/0"; CFileDialog dlgFile(bOpenFileDialog, NULL, NULL, OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT, strFilter, NULL, 0); CString title; VERIFY(title.LoadString(nIDSTitle)); dlgFile.m_ofn.lpstrFilter = strFilter; dlgFile.m_ofn.lpstrDefExt = _T(".aaa"); dlgFile.m_ofn.lpstrTitle = title; dlgFile.m_ofn.lpstrFile = fileName.GetBuffer(_MAX_PATH);
INT_PTR nResult = dlgFile.DoModal(); fileName.ReleaseBuffer(); return nResult == IDOK; } CSDIDocMgr是派生自CDocManager的类。下一步的问题是：怎么为CWinApp::m_pDocManager创建CSDIDocMgr对象（而非CDocManager对象）？m_pDocManager是在重写的CWinApp::InitInstance虚方法中创建的，具体来说，是在CWinApp::AddDocTemplate方法中创建的，CWinApp::AddDocTemplate方法在创建m_pDocManager之前会检查它是否为NULL，只有当m_pDocManager为NULL时才为它创建CDocManager对象，所以现在并不需要重写CWinApp::AddDocTemplate方法，而只需要在重写的CWinApp::InitInstance方法中、在调用CWinApp::AddDocTemplate方法之前为m_pDocManager创建CSDIDocMgr对象。 一旦重写了CDocManager::DoPromptFileName方法，之前提到的自定义打开对话框文件扩展名的方法也就多此一举了，也不再需要修改资源文件中的IDR_DTriNetTYPE字段，因为无论打开还是保存对话框，最终都是由CDocManager::DoPromptFileName执行的。
