一、QFile读写文本

//例1
    QFile file("textFile1.txt");
    if(file.open(QIODevice::ReadOnly))  //以只读方式打开文件
    {
       char buffer[2048];
       //读取一行数据
       qint64 lineLen = file.readLine(buffer,sizeof(buffer)); 
       if(lineLen!=-1)  //读取失败返回-1
       {
           qDebug()<<buffer;
       }
    }
//例2
    QFile file("in.txt");
    //QIODevice::Text：将("\r\n")转换C++风格("\n")
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return;

    while (!file.atEnd()) {
        QByteArray line = file.readLine();
        process_line(line);
    }

二、QTextStream读写文本

//例1
    QFile data("data.txt");
    //QFile::Truncate:将原来文件中的内容清空
    if(data.open(QFile::WriteOnly|QFile::Truncate))
    {
        QTextStream out(&data);
        //qSetFieldWidth：设置字段宽度
        //left:左对齐
        out<<QObject::tr("score:")<<qSetFieldWidth(10)<<left<<90<<endl;
    }
//例2
    QFile file("in.txt");
    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
        return;
    //转换成流，因为以QIODevice::ReadOnly打开，所以是输入流
    QTextStream in(&file);
    while (!in.atEnd()) {
        QString line = in.readLine();
        process_line(line);
    }
//例3
    QFile file("out.txt");
    if (!file.open(QIODevice::WriteOnly | QIODevice::Text))
        return;

    QTextStream out(&file);
    out << "The magic number is: " << 49 << "\n";

三、读写二进制文件

QFile file("binary.dat");
    file.open(QIODevice::WriteOnly | QIODevice::Truncate);
    QDataStream out(&file);                             //将数据序列化
    out << QString(tr("周何骏："));                      //字符串序列化
    out << QDate::fromString("1994/09/25", "yyyy/MM/dd");
    out << (qint32)19;                                  //整数序列化
    file.close();

    file.setFileName("binary.dat");
    if(!file.open(QIODevice::ReadOnly))
    {
         qDebug()<< "error!";
         return;
    }
    QDataStream in(&file);                              //从文件中读出数据
    QString name;
    QDate birthday;
    qint32 age;
    //要按顺序读取，否则会出现问题
    in >> name >> birthday >> age;                      //获取字符串和整数
    qDebug() << name << birthday << age;
    file.close();