Qt 实现文件复制 界面有进度条(根据文件大小)显示复制进度，

 char* byteTemp = new char[4096];//字节数组

    int fileSize = 0;

    int totalCopySize = 0;

    QFile tofile;

    ui->progressBar_copy->setValue(0);

    tofile.setFileName(toFileName);

    if(!tofile.open(QIODevice::WriteOnly))

    {

        qDebug() << "open fromfile failed2！！！";

        return false;

    }

    QDataStream out(&tofile);

    out.setVersion(QDataStream::Qt_4_0);

    QFile fromfile;

    fromfile.setFileName(fromFIleName);

    if(!fromfile.open(QIODevice::ReadOnly)){

        qDebug() << "open fromfile failed！！！";

        return false;

    }

    fileSize = fromfile.size();

    QDataStream in(&fromfile);

    in.setVersion(QDataStream::Qt_4_0);

    qDebug()<<"~~~~~~~"<<QString::number(fileSize);

    ui->progressBar_copy->setRange(0, fileSize);

    while(!in.atEnd())

    {

        int readSize = 0;

        //读入字节数组,返回读取的字节数量，如果小于4096，则到了文件尾

        readSize = in.readRawData(byteTemp, 4096);

        out.writeRawData(byteTemp, readSize);

        totalCopySize += readSize;

        ui->progressBar_copy->setValue(totalCopySize);

    }

    if(totalCopySize == fileSize){

        tofile.setPermissions(QFile::ExeUser);

        tofile.close();

        fromfile.close();

        return true;

    }

    else

        return false;