problem in writing text with QFile

[wei243]

QFile file(fileName);
file.open(QIODevice::WriteOnly);
QDataStream out(&file);
QApplication::setOverrideCursor(Qt::WaitCursor);
out << "TESTING";
QApplication::restoreOverrideCursor();
file.close();

QFile file(fileName);
file.open(QIODevice::WriteOnly);
QDataStream out(&file);
QApplication::setOverrideCursor(Qt::WaitCursor);
out << "TESTING";
QApplication::restoreOverrideCursor();
file.close();

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after i run above code the text file bcome
untitled.JPG

pls help me slove this problem...
thx

[wysota]

Use QTextStream instead of QDataStream. The latter is for serialization.

[wei243]

i m going to use QTcpSocket to send a QByteArray(which carry a file's content) to receiver.
i use QDataStream here, bcoz the file can be any type(text file, picture file and etc).

wat i did in my sender program is:

quint64 maxSize;
QByteArray Data;
QFile file(fileName);
Data = file.read(maxSize);

QTcpSocket *tcpSocket = new QTcpSocket;
tcpSocket->abort();

tcpSocket->connectToHost(targetIP,targetPort);

QByteArray block;
QDataStream out_s(&block,QIODevice::WriteOnly);
out_s.setVersion(QDataStream::Qt_4_0);

out_s << (quint64)0;
out_s << Data;
out_s.device()->seek(0);
out_s << (quint64)(block.size() - sizeof(quint64));
tcpSocket->write(block);
tcpSocket->disconnect();

is it any solution available?

i should use quint64 or quint16 here?

[wysota]

1. Seeking in a socket device doesn't make sense as it is not a random access device.
2. If you use QDataStream, you don't need to send the size of QByteArray as QDataStream will do that for you. Remember that this is a serialization mechanism, not a simple binary stream.
3. connectToHost() is an asynchronous call - you have to wait for the connection to be established before sending/receiving any data. The same goes for disconnectFromHost (I think you meant that and not disconnect(), right?).

[wei243]

thx wysota.

QTextStream slove my 1st problem in writing text to a file.

QFile file(filename);
file.open(QIODevice::WriteOnly);
QTextStream textstream(&file);
textstream << text;

i apply it in writing a picture file with QDataStream.
but nothing appear in the picture file.
wat should i do?

[wysota]

i apply it in writing a picture file with QDataStream.
but nothing appear in the picture file.
wat should i do?

You can't use a text stream to handle binary data... I suggest you don't use streams at all with binaries or use QDataStream::readRawData and QDataStream::writeRawData instead of << and >> operators.