1.widget.h

#include <QPainter>         //画家
#include <QTimerEvent>
#include <QTime>
#include<QTimer>    //定时器类

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

    void paintEvent(QPaintEvent *event) override;

    //定时器处理函数
     void timerEvent(QTimerEvent *e) override;



private:
    Ui::Widget *ui;
     int timer_id;

};
#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);

      timer_id = this->startTimer(1000);
}

Widget::~Widget()
{
    delete ui;
}

void Widget::paintEvent(QPaintEvent *event)
{
   // static int num=1;
    //qDebug()<<num++;
    QPainter painter(this);
    //
    QPen pen;
    pen.setColor(QColor("blue"));
    pen.setStyle(Qt::SolidLine);
    pen.setWidth(5);
    //
    painter.setPen(pen);
    //
    painter.translate(this->width()/2,this->height()/2);
    //设置画刷和偏移坐标系
    painter.rotate(0);
    painter.setBrush(QBrush(QColor("skyblue")));
    //画个圆
    painter.drawEllipse(QPoint(0,0),100,100);

    for(int i=0;i<360;i+=30)
    {
        painter.rotate(30);
        painter.drawLine(QPoint(0,-100),QPoint(0,-90));

    }
    for(int i=0;i<360;i+=6)
    {
        painter.rotate(6);
        painter.drawLine(QPoint(0,-100),QPoint(0,-95));

}


    //绘制时针
    painter.save();    // 保存当前的绘制状态
        // 将绘制的坐标原点移动到表盘的中心
    int h=ui->label->text().toInt();    // 获取当前的小时
    int m=ui->label_2->text().toInt();     // 获取当前的分钟
    double hourAngle = (h%12 + m/60.0)*30.0;  // 计算时针的角度，考虑分钟对时针的影响
    painter.rotate(hourAngle);    // 旋转坐标系，使时针指向正确的位置
    painter.setPen(QPen(Qt::black,5));    //设置笔

    painter.drawLine(QPoint(0,0),QPoint(0,-30));  // 绘制时针，起点是坐标原点 (0, 0)，终点是时针的末端位置
    painter.restore();       // 恢复之前保存的绘制状态，以便后续绘制

    //绘制分针
    painter.save();

    double minuteAngle = m*6.0;
    painter.rotate(minuteAngle);
    painter.setPen(QPen(Qt::red,3));        //设置笔
    painter.drawLine(QPoint(0,0),QPoint(0,-50));
    painter.restore();

    //绘制秒针
    painter.save();


    int s=ui->label_3->text().toInt();
    double secondAngle = s * 6.0;
    painter.rotate(secondAngle);
    painter.setPen(QPen(Qt::blue,2));      //设置笔
    painter.drawLine(QPoint(0,0),QPoint(0,-70));
    painter.restore();
    this->update();

}



void Widget::timerEvent(QTimerEvent *e)
{

        if(e->timerId()==timer_id)
        {

            static QTime sys_t=QTime::currentTime();
            QString h=sys_t.toString("hh");
            QString m=sys_t.toString("mm");
            QString s=sys_t.toString("ss");

            ui->label->setText(h);
            ui->label_2->setText(m);
            ui->label_3->setText(s);
        }

}

main.cpp

#include "widget.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    return a.exec();
}