利用QT实现时钟

原理

QPainter 提供了绘图的常用操作，QTimer 提供了定时器功能，两者结合，可以绘制出各种不同风格的时钟。

实现方式

绘制时钟，包括时针、分针、秒针、刻度等。

void AnalogClock::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);
    //表针初始位置
    static  QPoint hourHand[3] = 
    {
        QPoint(8, 8),
        QPoint(-8, 8),
        QPoint(0, -40)
    };
    static  QPoint minuteHand[3] = 
    {
        QPoint(6, 9),
        QPoint(-6, 9),
        QPoint(0, -70)
    };
    static  QPoint secondHand[3] = 
    {
        QPoint(5, 10),
        QPoint(-5, 10),
        QPoint(0, -90)
    };
    QColor hourColor(225, 255, 255);
    QColor minuteColor(176, 224, 230, 191);
    QColor secondColor(0,206,209);



    int side = qMin(width(), height());
    QTime time = QTime::currentTime();
    QPainter painter(this);



    QPixmap pixmap(":/5.jpg");//背景图
    painter.drawPixmap(0,0,width(),height(),pixmap);

    //表盘
    painter.setRenderHint(QPainter::Antialiasing);//去锯齿
    painter.translate(width()/2, height()/2);
    painter.scale(side /250.0, side /250.0);
  
    //时针
    painter.setPen(Qt::NoPen);
    painter.setBrush(hourColor);
    painter.save();
    painter.rotate(30.0 * (time.hour() + time.minute() / 60.0));
    painter.drawConvexPolygon(hourHand, 3);
    painter.restore();


    //分针
    painter.setPen(Qt::NoPen);
    painter.setBrush(minuteColor);
    painter.save();
    painter.rotate(6.0 * (time.minute() + time.second() / 60.0));
    painter.drawConvexPolygon(minuteHand, 3);
    painter.restore();


    //秒针
    painter.setPen(Qt::NoPen);
    painter.setBrush(secondColor);
    painter.save();
    painter.rotate(6.0 * time.second());
    painter.drawConvexPolygon(secondHand, 3);
    painter.restore();

     //画小时文本
    painter.setPen(hourColor);
    int r=108;
    QFont font=painter.font();
    int pointSize=font.pointSize();
    for(int i=0;i<12;i++)
    {
        int num;
        if(i==0)
            num=12;
        else
            num=i;
         painter.drawText(textRectF(r,pointSize,i*30-90),Qt::AlignCenter,QString::number(num));
    }

    //画表盘时线
    painter.setPen(hourColor);
    for (int i = 0; i <12; i++)
    {
        painter.drawLine(0, 88, 0, 96);
        painter.rotate(30.0);
    }


    //画钟盘分线
    painter.setPen(Qt::NoPen);
    painter.setPen(minuteColor);
    for (int j = 0; j < 60; ++j) 
    {
        if ((j % 5) != 0)
            painter.drawLine(92, 0, 96, 0);
        painter.rotate(6.0);
    }


}

绘制小时对应的数字，通过 textRectF() 实现

//绘制文本区域
QRectF AnalogClock::textRectF(double r, int pointSize, double angle)
{
    QRectF rectf;
    //pointsize字体大小
    rectf.setX(r*qCos(angle*M_PI/180.0)-pointSize*2);
    rectf.setY(r*qSin(angle*M_PI/180.0)-pointSize);
    rectf.setWidth(pointSize*4);
    rectf.setHeight(pointSize*2);
    return rectf;
}

analogclock.h

#ifndef ANALOGCLOCK_H
#define ANALOGCLOCK_H

#include <QWidget>
#include<QPoint>
#include<QPainter>


class AnalogClock : public QWidget
{
    Q_OBJECT

public:
    AnalogClock(QWidget *parent = nullptr);
    ~AnalogClock();
  
    void paintEvent(QPaintEvent *event);
    QRectF textRectF(double r,int pointSize,double angle);
private:
    QPoint m_point;
    Ui::AnalogClock *ui;
};
#endif // ANALOGCLOCK_H

实现转动

首先，我们构造一个定时器 QTimer，连接其超时信号 timeout() 到槽函数 update()，当调用 update() 时，系统会自动通知当前界面进行重绘paintEvent()。

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

    QTimer *timer = new QTimer(this);
  
        connect(timer, SIGNAL(timeout()), this, SLOT(update()));
              timer->start(1000)；


}