QT 向txt中写入数据

       QDir *TEST = new QDir(QDir::currentPath());
        bool exist = TEST->exists("Signal");
        if(!exist)
        {
         TEST->mkdir("Signal");
        }
         QString fileNameGPS = "Signal/GPS.txt";
         QFile fileGPS(fileNameGPS);
         if(!fileGPS.open(QIODevice::WriteOnly|QIODevice::Text))
         {
            QMessageBox::warning(this,"sdf","can't open",QMessageBox::Yes);
         }
         QTextStream in(&fileGPS);
         for (int i=0;i<g_GNGSV->GPGSVAvgSNRList.length();i++)
         {
             double GPSDB=  g_GNGSV->GPGSVAvgSNRList.at(i);
             //处理读取文件的信噪比为空的情况
             if(GPSDB<0.1)
             {
                 in<<QString::number(GPSDB)+"\r\n";
             }
             else
             {
                 in<<"NaN"<<"\r\n";
             }
         }