why the qt application's font can't display on phone?

for example


#include <qapplication>
#include <qpushbutton>


int main( int argc, char **argv )
{
QApplication a( argc, argv );

QPushButton hello( "Hello world!", 0 );
hello.resize( 100, 30 );

a.setMainWidget( &hello );
hello.show();
return a.exec();
}

"Hello world" and menubar's font cant display .....

a long time ago it can work ,bu recently i recompile coss-compler

programe come out, anyone can tell me why?

thank you!!!