头文件

#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>
#include <QPainter>
#include <QTime>
#include <QTimerEvent>
#include <QDebug>QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACEclass Widget : public QWidget
{Q_OBJECTpublic:Widget(QWidget *parent = nullptr);~Widget();void paintEvent(QPaintEvent *event) override;private:Ui::Widget *ui;//声明 事件处理函数 重载void timerEvent(QTimerEvent *event) override;};
#endif // WIDGET_H

原文件

#include "widget.h"
#include "ui_widget.h"Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);this->startTimer(1000);
}Widget::~Widget()
{delete ui;
}//时钟底座
void Widget::paintEvent(QPaintEvent *event)
{   QPainter painter(this);//实例化画家QPen pen;//实例化笔QFont font;//实例化字体//画笔属性pen.setWidth(5);//字体属性font.setFamily("楷体");font.setPointSize(10);//画家属性painter.setPen(pen);painter.setFont(font);painter.translate(this->width()/2,this->height()/2);//画家坐标//绘制圆painter.drawEllipse(QPoint(0,0),300,300);//绘制粗刻度painter.rotate(-60);for(int i = 0; i < 12; i++){painter.drawLine(300,0,290,0);painter.rotate(30);}//绘制细刻度pen.setWidth(2);painter.setPen(pen);painter.rotate(-24);for(int i = 0; i < 60 ; i++){painter.drawLine(300,0,295,0);painter.rotate(6);}//获取系统时间QTime time = QTime::currentTime();//绘制秒针painter.setPen(pen);painter.rotate(-6);painter.rotate(6*time.second());painter.drawLine(290,0,0,0);painter.rotate(-6*time.second());//绘制分针pen.setWidth(10);painter.setPen(pen);painter.rotate(6*time.minute());painter.drawLine(200,0,0,0);painter.rotate(-6*time.minute());//绘制时针pen.setWidth(15);painter.setPen(pen);painter.rotate(30*time.hour());painter.drawLine(100,0,0,0);qDebug()<<time.hour()<<" "<<time.minute()<<" "<<time.second();
}void Widget::timerEvent(QTimerEvent *event)
{this->update();
}