源代码以及解释

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

main.cpp文件没啥好解释的

#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
namespace Ui {
class Widget;
}
class Widget : public QWidget
{
    Q_OBJECT
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();
protected:
    void paintEvent(QPaintEvent *e);
private:
    Ui::Widget *ui;
};
#endif // WIDGET_H

widget.h文件,这里用的是ui界面文件,而不是纯代码创建。但主要的绘制工作还是在paintEvent.

// //////yiniao颜色用cos
#include "widget.h"
#include "ui_widget.h"
#include <QtGui>
#include <QTime>
#include <QDebug>
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    //一秒更新一次,repaint
    QTimer *timer = new QTimer(this);
    connect(timer,SIGNAL(timeout()),this,SLOT(repaint()));
    timer->start(1000);
    this->setWindowTitle(tr("Clock"));
    this->resize(400,400);
}
Widget::~Widget()
{
    delete ui;
}
void Widget::paintEvent(QPaintEvent *e)
{
//时分秒指针颜色
    QColor hourColor(127,0,127);
    QColor minuteColor(0,127,127,191);
    QColor secColor(Qt::black);
    int side = qMin(this->width(), this->height());
    QTime time = QTime::currentTime();
//正式开始绘画
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);//无锯齿
    painter.translate(this->width()/2, this->height()/2);//将坐标系原点移动到正中心
    painter.scale(side/200.0, side/200.0);//
    painter.setPen(Qt::NoPen);
    painter.setBrush(QBrush(hourColor));//绘制特殊图形,用brush
    painter.save();//保存当前painter状态
    painter.rotate(30.0 * (time.hour() + time.minute()/60.0));//坐标系旋转,根据真实时间确定旋转角度
    static const QPoint hourHand[3] = {
        QPoint(7,8),
        QPoint(-7,8),
        QPoint(0,-40)
    };//
    painter.drawConvexPolygon(hourHand, 3);  //画不规则多边形
    painter.restore();//恢复save前原来的坐标系
    painter.setPen(hourColor);//画刻度线,用Pen,不用Brush
    for(int i=0; i<12; i++){
        painter.drawLine(88,0,96,0);//12小时对应的刻度
        painter.rotate(30.0);
    }
//画1-12数字,根据数学半径sin,cos计算所画text的位置
    int textR = 80;     //big ridaus
    int textW = 12;   //width = height
    int textH = 8;
    const double pi = 3.1415926;
    for(int i=0; i<12; i++){
        double angle = 30.0 * i * pi/ 180;
        int x = textR * cos(angle) - textW/2;
        int y = textR * sin(angle) - textH/2;
        //qDebug()<<i<<angle<<x<<y;
        painter.drawText(QRect(x, y, textW, textH), Qt::AlignCenter,
                         QString("%1").arg((i+3)>12?(i+3-12):(i+3)));
    }
//画分,同上
    painter.setPen(Qt::NoPen);
    painter.setBrush(QBrush(minuteColor));
    painter.save();
    painter.rotate(6.0 * (time.minute() + time.second()/60.0));
    static const QPoint minuteHand[3] = {
        QPoint(7,8),
        QPoint(-7,8),
        QPoint(0,-70)
    };
    painter.drawConvexPolygon(minuteHand, 3);
    painter.restore();
    painter.setPen(minuteColor);
    for (int j=0; j<60; j++){
        if ((j%5) != 0){
            painter.drawLine(92, 0, 96, 0);
        }
        painter.rotate(6.0);
    }
//画秒,同上
    painter.setPen(Qt::NoPen);
    painter.setBrush(QBrush(secColor));
    painter.save();
    painter.rotate(time.second() * 6.0);
    static const QPoint secHand[3] = {
        QPoint(3,4),
        QPoint(-3,4),
        QPoint(0,-85)
    };
    painter.drawConvexPolygon(secHand, 3);
    painter.restore();
}

运行结果:

142725349.png

下一步,可以加上年月日的显示,待续。。。