使用Qt创建模拟时钟

main.cpp

 #include
 #include "analogclock.h"

 Q_DECL_EXPORT int main(int argc, char *argv[])
 {
     QApplication theApp(argc, argv);

     AnalogClock clock;
     clock.show();

     return theApp.exec();
 }

analogclock.h

 #ifndef ANALOGCLOCK_H
 #define ANALOGCLOCK_H

 #include

 class AnalogClock : public QWidget
 {
     Q_OBJECT
 public:
     explicit AnalogClock(QWidget *parent = 0);

 signals:

 public slots:

 protected:
      void paintEvent(QPaintEvent *event);
 };

 #endif // ANALOGCLOCK_H void paintEvent(QPaintEvent *event);

analogclock.cpp

 #include
 #include "analogclock.h"

 AnalogClock::AnalogClock(QWidget *parent) :
     QWidget(parent)
 {
     QTimer* timer = new QTimer(this);
     connect(timer, SIGNAL(timeout()), this, SLOT(update()));
     timer->start(1000);
     setWindowTitle(tr("Analog Clock"));
     resize(200, 200);

 }

 void AnalogClock::paintEvent(QPaintEvent *)
 {
     // 时针和分针的点坐标
     //画的是三角形，所以需要三个点的坐标
     static const QPoint hourHand[3] = {
         QPoint(7, 8),
         QPoint(-7, 8),
         QPoint(0, -30)
     };
     static const QPoint minuteHand[3] = {
         QPoint(7, 8),
         QPoint(-7, 8),
         QPoint(0, -60)
     };

     static const QPoint secondHand[3] = {
         QPoint(4, 8),
         QPoint(-4, 8),
         QPoint(0, -100)
     };

     /* 设置时针和分针的颜色 */
     QColor hourColor(127, 0, 127);
     QColor minuteColor(0, 127, 127, 191);
     QColor secondColor(0, 100, 100);

     /* QT自带函数，返回两个数的最小值 */
     int side = qMin(width(), height());

     /* 获取当前时间 */
     QTime time = QTime::currentTime();

     /*
         在this这个可绘画设备上创建一个绘画者
         设置渲染，用反锯齿效果
         用一个重载函数转换一下坐标系
         缩放一下这个坐标系
     */
     //The QPainter class performs low-level painting on widgets and other paint devices.
     QPainter painter(this);

     //Sets the given render hint on the painter if on is true; otherwise clears the render hint
     //Renderhints are used to specify flags to QPainter that may or may not be respected by any given engine.
     painter.setRenderHint(QPainter::Antialiasing);

     //Translates the coordinate system by the given offset
     painter.translate(width()/2, height()/2);

     //Scales the coordinate system by (sx, sy).
     painter.scale(side/200.0, side/200.0);

     /* 用一个重载函数设置一下画笔的类型，NoPen就是没有线
        再用一个重载函数设置一下笔刷的颜色，用默认类型
     */
     //Sets the painter's pen to be the given pen.
     //The pen defines how to draw lines and outlines, and it also defines the text color.
     painter.setPen(Qt::NoPen);

     //sets the painter's brush to the given brush.
     //The painter's brush defines how shapes are filled.
     painter.setBrush(hourColor);

     //Saves the current painter state (pushes the state onto a stack).
     //A save() must be followed by a corresponding restore(); the end() function unwinds the stack.
     painter.save(); //保存当前的绘画者状态

     //用给出的角度旋转坐标系
     //Rotates the coordinate system the given angle clockwise.
     painter.rotate(30.0*((time.hour()+time.minute()/60.0)));

     //用线把点连起来
     //Draws the convex polygon defined by the first pointCount points in the array points using the current pen.
     //The first point is implicitly connected to the last point, and the polygon is filled with the current brush().
     painter.drawConvexPolygon(hourHand, 3);

     //恢复当前的绘画者状态
     //Restores the current painter state (pops a saved state off the stack).
     painter.restore();

     painter.setPen(hourColor);

     /* 画代表小时的线 */
     for (int i = 0; i < 12; ++i) {
         //Draws a line from (x1, y1) to (x2, y2) and sets the current pen position to (x2, y2).
         painter.drawLine(88, 0, 96, 0);
         painter.rotate(30.0);
     }

     //下面画分钟的过程是上面的重复，只是分针的颜色用到了透明度
     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();
     painter.setPen(minuteColor);

     /* 画代表分钟的线 */
     for (int j = 0; j < 60; ++j) {
         if((j % 5) != 0) {
             painter.drawLine(92, 0, 96,0);
         }
         painter.rotate(6.0);
     }

     //下面画秒针的过程是上面的重复
     painter.setPen(Qt::NoPen);
     painter.setBrush(secondColor);
     painter.save();
     painter.rotate(6.0*(time.second()));
     painter.drawConvexPolygon(secondHand, 3);
     painter.restore();
     painter.setPen(minuteColor);
 }

FROM: http://www.cnblogs.com/johnpher/archive/2012/01/01/2570587.html