MFC保存文件对话框

Question

我正在编写一个MFC C++应用程序,它有一个"另存为"按钮,用于将.txt文件保存到光盘.有了它,我试图为文件覆盖添加额外的验证(如果存在具有相同文件名的文件,那么它应该查询用户是否要覆盖旧文件).我用下面的代码试过这个,但它确实不起作用.当我在MessageBox上单击No时,它应该重新打开另存为文件对话框,但它会给我两个错误:第一个是Debug assertion failed,第二个是Encountered an improper argument.我该怎么做得更好？这是代码:

char strFilter[] = { "Text Files (*.txt)|*.txt|" }; 

    CFileDialog FileDlg(FALSE, CString(".txt"), NULL, 0, CString(strFilter)); 

    while(true)
    {
        if( FileDlg.DoModal() == IDOK ) // this is the line which gives the errors
        {
            agendaName = FileDlg.GetFileName(); //filename
            agendaPath = FileDlg.GetFolderPath(); //filepath (folders)

            if(model->agendaExists(CSToString(agendaPath+TEXT("\\")+agendaName))) // there is another file called the same way
            {
                if(MessageBox(TEXT("A file with the specified name already exists. Overwrite?"), TEXT("File exists"), MB_YESNO) != 6) // user clicked NO (do not overwrite file)
                {
                    continue;
                }

            }

            model->sendToFile(CSToString(agendaPath+TEXT("\\")+agendaName));  // the file is unique so the agenda named agendaName found at path agendaPath is saved
            return;
        }
    }

应该提到的是,错误发生在第7行,而只发生在第二个循环中while.

Answer 1

如果文件存在,CFileDialog可以检测自身并提示用户覆盖.

explicit CFileDialog(
   BOOL bOpenFileDialog,
   LPCTSTR lpszDefExt = NULL,
   LPCTSTR lpszFileName = NULL,
   DWORD dwFlags = OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,
   LPCTSTR lpszFilter = NULL,
   CWnd* pParentWnd = NULL,
   DWORD dwSize = 0
);

只需传递OFN_OVERWRITEPROMPT标志即可.

至于你的问题,在Debugger中运行,当你得到那个断言时,按Retry按钮查看问题的来源(你可能还需要查看调用堆栈).也许你应该尝试把它放在while循环中:

CFileDialog FileDlg(FALSE, CString(".txt"), NULL, 0, CString(strFilter));