通过代码实现电子钟表

头文件

#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>
#include<QPaintEvent>
#include<QDebug>
#include<QPainter>
#include<QFont>
#include<QTime>
#include<QTimer>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;int m_sec = 0;int m_min = 0;int m_hour = 0;QTimer *timer;void timeout_slot();
};
#endif // WIDGET_H

源文件

#include "widget.h"
#include "ui_widget.h"Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);timer = new QTimer(this);timer->start(1000);//一秒钟connect(timer, &QTimer::timeout, this, &Widget::timeout_slot);
}Widget::~Widget()
{delete ui;
}void Widget::paintEvent(QPaintEvent *event)
{//实例化画家1QPainter painter(this);//实例化一个画笔QPen pen;       //使用无参构造pen.setColor(QColor("black"));      //设置画笔颜色//pen.setStyle(Qt::DashDotDotLine);   //设置线型pen.setWidth(5);                    //设置画笔宽度//将画笔给画家painter.setPen(pen);//给画家安排画刷painter.setBrush(QBrush(QColor("skyblue")));//给画家偏移起始坐标点painter.translate(this->width()/2, this->height()/2);//给画家偏移坐标系//painter.rotate(0);          //旋转坐标系//画个椭圆painter.drawEllipse(QPoint(0,0), 200, 200);//画刻度线for(int i = 1; i <=60; ++i){painter.save();painter.rotate(6*i);//坐标轴旋转6度if (i % 5 == 0){painter.drawLine(0, -188, 0, -200);painter.drawText(QPoint(-6,-160), QString::number(i/5));}else{painter.drawLine(0, -192, 0, -200);}painter.restore();//绘制图形后复位坐标系}painter.save();painter.rotate(6*m_sec);painter.drawLine(0,0,0,-170);painter.restore();painter.save();double m = (m_min*6.0 + m_sec*0.1);painter.rotate(m);painter.drawLine(0,0,0,-140);painter.restore();painter.save();double h = (m_hour%12 + m_min/60.0)*30.0;painter.rotate(h);painter.drawLine(0,0,0,-110);painter.restore();}void Widget::timeout_slot()
{QDateTime datetime = QDateTime::currentDateTime();m_sec = datetime.time().second();m_min = datetime.time().minute();m_hour = datetime.time().hour();update();
}

主函数

#include "widget.h"#include <QApplication>int main(int argc, char *argv[])
{QApplication a(argc, argv);Widget w;w.show();return a.exec();
}

效果展示