我只找到了这种方式
QStyle * QApplication::setStyle ( const QString & style ) [static]
This is an overloaded function.
Requests a QStyle object for style from the QStyleFactory.
The string must be one of the QStyleFactory::keys(), typically one of "windows", "motif", "cde", "plastique", "windowsxp", or "macintosh". Style names are case insensitive.
Returns 0 if an unknown style is passed, otherwise the QStyle object returned is set as the application's GUI style.
Warning: To ensure that the application's style is set correctly, it is best to call this function before the QApplication constructor, if possible.