qt-读写文件QTextStream

//获取根路径
    QString runPath = QCoreApplication::applicationDirPath();//获取项目的根路径
    QString file_name = QFileDialog::getOpenFileName(this, QStringLiteral("选择文件"), runPath, "Text Files(*.dat)", nullptr, QFileDialog::DontResolveSymlinks);
    QFile myFile(file_name);
    //写文件
    QFile myFile_write("C:/Users/lenovo/Documents/2.dat");
    if (!myFile_write.open(QIODevice::WriteOnly))
    {
        qDebug() << myFile_write.errorString();
    }
    //写文件---可以用作另存
    QTextStream textStream_write(&myFile_write);
    textStream_write << str1;
        textStream_write << ",";
    textStream_write << str2;
    textStream_write << "  __  ";
    textStream_write << count_line;
    textStream_write << "\n";
    textStream_write.flush();
    //读取文件
    if (!myFile.open(QIODevice::ReadOnly))
    {
        qDebug() << myFile.errorString();
    }
    QTextStream textStream(&myFile);
    textStream.setDevice(&myFile);
    int count_line = 0;                        //文件行数
    QVector<double> point_x, point_y;        //x，y容器
    while (!textStream.atEnd())
    {
        QString str = textStream.readLine();
        QString str_first = *str.begin();
        if (str_first =="%")
        {
            continue;
        }
        double str1 = str.split(",",QString::SkipEmptyParts)[0].toDouble();
        double str2 = str.split(",",QString::SkipEmptyParts)[1].toDouble();
        point_x.push_back(str1);
        point_y.push_back(str2);
        count_line++;
    }
    textStream.seek(0);
    myFile_write.close();