这是我编的一段程序,请问如何能实现实时显示呢 
class MyMainWindow : public QWidget
{
        public:
                MyMainWindow();
        private:
                QLabel *c_label;
                QLabel *d_label;
                QLabel *t_label;
                QLabel *n_label;
                QLabel *c_line;
                QLabel *d_line;
                QLabel *t_line;
                QLabel *n_line;
};
MyMainWindow::MyMainWindow()
{
        setMinimumSize(320,240);
        setMaximumSize(320,240);
        QDate date=QDate::currentDate();
        QTime time=QTime::currentTime();
//      QTimer *timer = new QTime(t_line);
//      QTimer *timec = new QTime(t_line);
        c_label=new QLabel(this);
        d_label=new QLabel(this);
        t_label=new QLabel(this);
        n_label=new QLabel(this);
        c_label->setGeometry(40,20,60,40);
        c_label->setText("class:");
        c_label->setAlignment(Qt::AlignCenter);
        c_label->setFont(QFont("Time",16));
        d_label->setGeometry(40,70,60,40);
        d_label->setText("data:");
        d_label->setAlignment(Qt::AlignCenter);
        d_label->setFont(QFont("Time",16));
        t_label->setGeometry(40,120,60,40);
        t_label->setText("time:");
        t_label->setAlignment(Qt::AlignCenter);
        t_label->setFont(QFont("Time",16));
        n_label->setGeometry(40,170,60,40);
        n_label->setText("num:");
        n_label->setAlignment(Qt::AlignCenter);
        n_label->setFont(QFont("Time",16));
        c_line=new QLabel("4301",this);
        d_line=new QLabel(date.toString(),this);
        t_line=new QLabel(time.toString(),this);
        n_line=new QLabel(this);
        c_line->setGeometry(110,20,170,40);
        c_line->setFont(QFont("Time",16));
        d_line->setGeometry(110,70,170,40);
        d_line->setFont(QFont("Time",16));
       t_line->setGeometry(110,120,170,40);
        t_line->setFont(QFont("Time",16));
//      connect(timer,SIGNAL(timeout()),t_line,SLOT(show()));
//      connect(timec,SIGNAL(timeout()),t_line,SLOT(clear()));
//      timer->start(1000);
//      timec->start(2000);
        n_line->setGeometry(110,170,170,40);
        n_line->setFont(QFont("Time",16));
};
int main(int argc, char **argv)
{
        QApplication app(argc, argv);
        MyMainWindow mymainwindow;
        mymainwindow.show();
        return app.exec();
};