仍然是hello world
#include <qapplication.h>
#include <qpushbutton.h>
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();
}