自定义MFC打开/保存对话框的扩展名
这里的顶目名称是D-TriNet，文档扩展名是.dtn和.csv。
要让打开/保存对话框支持多个扩展名，最简单的方法是修改资源文件中的IDR_DTriNetTYPE字段：
STRINGTABLE
BEGIN
IDR_MAINFRAME "D-TriNet"
IDR_DTriNetTYPE "\nDTriNet\nD-TriNet\nD-TriNet
Files(*.dtn;*.csv)\n.dtn;.csv\nDTriNet.Document\nD-TriNet.Document"
END
这样做的不足是，文件虽然可以有多个扩展名，但仍然只分为两类："D-TriNet Files"和"All Files"。要想更细致地分类，需要重写相关的虚函数，具体做法不唯一，我觉得比较好的一种是重写CDocManager::DoPromptFileName。
下面的文字有些凌乱，因为它的内容是按照我的探索过程组织的。
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，CDTriNetApp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CDTriNetApp::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, &CDTriNetApp::OnFileOpen)
void CDTriNetApp::OnFileOpen()
{
LPCTSTR szFilter = L"DTriNet文件(*.dtn)|*.dtn|CSV文件(*.csv)|*.csv|所有文件(*.*)|*.*||";
CFileDialog oFileDlg(TRUE, L".dtn", NULL, 4|2, szFilter);
if(oFileDlg.DoModal() == IDOK)
OpenDocumentFile(oFileDlg.GetFileName());
// CDTriNetApp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)
// 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;
}
看起来，重写CDocManager::DoPromptFileName方法比重写CDocument::DoSave方法要省事些：
BOOL CDTriNetDocMgr::DoPromptFileName(CString& fileName, UINT nIDSTitle,
DWORD lFlags, BOOL bOpenFileDialog, CDocTemplate* pTemplate)
{
LPCTSTR strFilter = L"DTriNet文件(*.dtn)|*.dtn|CSV文件(*.csv)|*.csv|所有文件(*.*)|*.*||";
CFileDialog dlgFile(bOpenFileDialog, NULL, NULL, OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT, strFilter, NULL, 0);
CString title;
VERIFY(title.LoadString(nIDSTitle));
dlgFile.m_ofn.lpstrTitle = title;
dlgFile.m_ofn.lpstrFile = fileName.GetBuffer(_MAX_PATH);
INT_PTR nResult = dlgFile.DoModal();
fileName.ReleaseBuffer();
return nResult == IDOK;
}
CDTriNetDocMgr是派生自CDocManager的类。下一步的问题是：怎么为CWinApp::m_pDocManager创建CDTriNetDocMgr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CDTriNetDocMgr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。