How to read UTF-8 text from file using Qt?

Question

I have some problems with reading UTF-8 encoded text from file. My version reads only ASCII characters.

#include <QtCore>

int main()
{
    QFile file("s.txt");

    if (!file.open(QIODevice::ReadOnly | QIODevice::Text))
    {
        return -1;
    }

    QTextStream in(&file);
    while(!in.atEnd())
    {
        QString line = in.readLine();
        qDebug() << line;
    }
}

s.txt:

jąkać się
ślimak
śnieżyca

output:

"jka si" 
"limak" 
"nieyca"

What should I use?

Solution 1

See QTextStream::setCodec():

in.setCodec("UTF-8");

Solution 2

You shuold do:

QTextStream in(&file);
in.setCodec("UTF-8"); // change the file codec to UTF-8.

while(!in.atEnd())
{
    QString line = in.readLine();
    qDebug() << line.toLocal8Bit(); // convert to locale multi-byte string 
}

Solution 3

I was also having ???? when reading an XML file with QXmlStreamReader. I fixed it by calling this before reading the file:

QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8"));

Comments

[Maciej Ziarko]

I tried it and now all the non-ASCII characters are replaced with "?".

[Maciej Ziarko]

After it I get: "j?ka? si?" "?limak" "?nie?yca"

[edA-qa mort-ora-y]

Perhaps your qDebug output console doesn't support those characters. That'd be a reasonable source of the "?". Try showing the string in a QLabel on-screen.

[Maciej Ziarko]

It's not the issue. dDebug() << QString("śnieżyca"); works perfectly.

[John Flatness]

You're sure your input file is actually UTF-8?

[Maciej Ziarko]

4 text editors (Geany, jEdit, gedit, Kate) say it is UTF-8. And still I have my problem with "?".

[Yi Zhao]

What's your default locale? If qDebug() << QString("śnieżyca"); works perfectly, it means your system configured a non-ASCII locale. You should try qDebug() << line.toLocal8Bit();

[Maciej Ziarko]

OK, it eventually fixed my problem. Thanks!