1.头文件

#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>
#include <QPainter>
#include <QTimer>
#include <QTime>
#include <QPaintEvent>
#include <QDebug>
#include <QBrush>QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACEclass Widget : public QWidget
{Q_OBJECTpublic:Widget(QWidget *parent = nullptr);~Widget();//重写绘制事件事件处理函数void paintEvent(QPaintEvent *event) override;
private slots:void updateTime();private:Ui::Widget *ui;QTimer *timer;QPixmap dial;
};
#endif // WIDGET_H

2.源文件

#include "widget.h"
#include "ui_widget.h"Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);this->setFixedSize(600,600);QTimer *timer = new QTimer(this);connect(timer,&QTimer::timeout,this,&Widget::updateTime);timer->start(1000);this->setStyleSheet("background-color:white;");
}Widget::~Widget()
{delete ui;
}void Widget::paintEvent(QPaintEvent *event)
{Q_UNUSED(event);//实例化一个画家QPainter painter(this);//设置绘图器（QPainter）的渲染提示，开启抗锯齿效果painter.setRenderHint(QPainter::Antialiasing);//获取当前时间QTime currentTime = QTime::currentTime();int X=this->width()/2;int Y=this->height()/2;int radius=200;//绘制表盘painter.setPen(QPen(Qt::black,7));     //设置笔if(dial.isNull()){dial.load("E:\\clock.png");}if(!dial.isNull()){painter.drawPixmap(X-radius,Y-radius,radius*2,radius*2,dial);}//绘制时针painter.save();    // 保存当前的绘制状态painter.translate(X,Y);    // 将绘制的坐标原点移动到表盘的中心int hour = currentTime.hour();    // 获取当前的小时int minute = currentTime.minute();     // 获取当前的分钟double hourAngle = (hour%12 + minute/60.0)*30.0;  // 计算时针的角度，考虑分钟对时针的影响painter.rotate(-90);    // 将坐标系旋转，使12点位置对应0度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(0,0,0,-radius*0.5);  // 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();painter.translate(X,Y);double minuteAngle = minute*6.0;painter.rotate(-90);painter.rotate(minuteAngle);painter.setPen(QPen(Qt::red,3));        //设置笔painter.drawLine(0,0,0,-radius*0.7);painter.restore();//绘制秒针painter.save();painter.translate(X,Y);int second = currentTime.second();double secondAngle = second * 6.0;painter.rotate(-90);painter.rotate(secondAngle);painter.setPen(QPen(Qt::blue,2));      //设置笔painter.drawLine(0,0,0,-radius*0.9);painter.restore();}void Widget::updateTime()
{update();
}