Use QDomDocument
:
QDomDocument doc;
doc.setContent(<your xml>);
QDomNodeList elems = doc.elementsByTagName("myValue1");
if (!elems.isEmpty())
{
QDomElement el = elems.at(0).toElement();
if (!el.isNull())
{
if (el.hasAttribute("value"))
{
el.setAttribute("value", "2");
}
}
}
qDebug() << doc.toString();