[提问]QT时钟程序 [复制链接]

麻烦大家帮忙看下，为什么我的程序里时钟显示不变化，不能动态显示时间呢？
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);

        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));
        t_line->setText(time.toString("hh:mm:ss"));
        connect(timer,SIGNAL(timeout()),t_line,SLOT(update()));
       timer->start(1000);

        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();
};

QDate date=QDate::currentDate();
QTime time=QTime::currentTime();
QTimer *timer = new QTime(t_line);
这几个都定义在构造函数里，构造函数执行完，就被销毁了。
应该定义成类成员变量。

    //创建定时器
  slotShowDateTime();
    QTimer *timer = new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(slotShowDateTime()));
    timer->start(1000);


void MainWindow::slotShowDateTime()
{
    QDateTime date_time = QDateTime::currentDateTime();
    QString dateTime = date_time.toString("yyyy-MM-dd hh:mm:ss");
    label_time->setText(dateTime);
}

我想楼主一定是理解错了update这个函数的意思
确实是不可能动态，因为t_line->setText(time.toString("hh:mm:ss"));这句只在构造函数中执行了一次