Qt绘制时钟效果

ClockWidget::ClockWidget(QWidget *parent)
  : QWidget(parent)
{
  ...
 
  // 构造定时器，设置超时为 1 秒
  QTimer *timer = new QTimer(this);
  connect(timer, SIGNAL(timeout()), this, SLOT(update()));
  timer->start(1000);
  ...
}

QRectF ClockWidget::textRectF(double radius, int pointSize, double angle)
{
  QRectF rectF;
  rectF.setX(radius*qCos(angle*M_PI/180.0) - pointSize*2);
  rectF.setY(radius*qSin(angle*M_PI/180.0) - pointSize/2.0);
  rectF.setWidth(pointSize*4);
  rectF.setHeight(pointSize);
  return rectF;
}

void ClockWidget::paintEvent(QPaintEvent *event)
{
  Q_UNUSED(event);
 
  // 时针、分针、秒针位置 - 多边形
  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, -65)
  };
 
  static const QPoint secondHand[3] = {
    QPoint(7, 8),
    QPoint(-7, 8),
    QPoint(0, -80)
  };
 
  // 时针、分针、秒针颜色
  QColor hourColor(200, 100, 0, 200);
  QColor minuteColor(0, 127, 127, 150);
  QColor secondColor(0, 160, 230, 150);
 
  int side = qMin(width(), height());
  QTime time = QTime::currentTime();
 
  QPainter painter(this);
  painter.setRenderHint(QPainter::Antialiasing);
  // 平移坐标系原点至中心点
  painter.translate(width() / 2, height() / 2);
  // 缩放
  painter.scale(side / 200.0, side / 200.0);
 
  // 绘制时针
  painter.setPen(Qt::NoPen);
  painter.setBrush(hourColor);
 
  painter.save();
  // 每圈360° = 12h 即：旋转角度 = 小时数 * 30°
  painter.rotate(30.0 * ((time.hour() + time.minute() / 60.0)));
  painter.drawConvexPolygon(hourHand, 3);
  painter.restore();
 
  painter.setPen(hourColor);
 
  // 绘制小时线 （360度 / 12 = 30度）
  for (int i = 0; i < 12; ++i) {
    painter.drawLine(88, 0, 96, 0);
    painter.rotate(30.0);
  }
 
  int radius = 100;
  QFont font = painter.font();
  font.setBold(true);
  painter.setFont(font);
  int pointSize = font.pointSize();
 
  // 绘制小时文本
  int nHour = 0;
  for (int i = 0; i < 12; ++i) {
    nHour = i + 3;
    if (nHour > 12)
      nHour -= 12;
    painter.drawText(textRectF(radius*0.8, pointSize, i * 30), Qt::AlignCenter, QString::number(nHour));
  }
 
  // 绘制分针
  painter.setPen(Qt::NoPen);
  painter.setBrush(minuteColor);
 
  painter.save();
  // 每圈360° = 60m 即：旋转角度 = 分钟数 * 6°
  painter.rotate(6.0 * (time.minute() + time.second() / 60.0));
  painter.drawConvexPolygon(minuteHand, 3);
  painter.restore();
 
  painter.setPen(minuteColor);
 
  // 绘制分钟线 （360度 / 60 = 6度）
  for (int j = 0; j < 60; ++j) {
    if ((j % 5) != 0)
      painter.drawLine(92, 0, 96, 0);
    painter.rotate(6.0);
  }
 
  // 绘制秒针
  painter.setPen(Qt::NoPen);
  painter.setBrush(secondColor);
 
  painter.save();
  // 每圈360° = 60s 即：旋转角度 = 秒数 * 6°
  painter.rotate(6.0 * time.second());
  painter.drawConvexPolygon(secondHand, 3);
  painter.restore();
}