QT 用 paintEvent 实现绘制钟表的列子

参见列子： C:\Qt\Qt5.5.1\Examples\Qt-5.5\widgets\widgets\shapedclock\shapedclock.pro

下面是效果图：



下面是代码：

#ifndef SHAPEDCLOCK_H
#define SHAPEDCLOCK_H

#include <QWidget>

//! [0]
class ShapedClock : public QWidget
{
Q_OBJECT

public:
ShapedClock(QWidget *parent = 0);
QSize sizeHint() const Q_DECL_OVERRIDE;

protected:
void mouseMoveEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
void mousePressEvent(QMouseEvent *event) Q_DECL_OVERRIDE;
void paintEvent(QPaintEvent *event) Q_DECL_OVERRIDE;
void resizeEvent(QResizeEvent *event) Q_DECL_OVERRIDE;

private:
QPoint dragPosition;
};
//! [0]

#endif

#include <QtWidgets>

#include "shapedclock.h"

#define clkAllSize 600
//! [0]
ShapedClock::ShapedClock(QWidget *parent)
: QWidget(parent, Qt::FramelessWindowHint | Qt::WindowSystemMenuHint)
{
QTimer *timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(update()));
timer->start(1000);

QAction *quitAction = new QAction(tr("E&xit"), this);
quitAction->setShortcut(tr("Ctrl+Q"));
connect(quitAction, SIGNAL(triggered()), qApp, SLOT(quit()));
addAction(quitAction);

setContextMenuPolicy(Qt::ActionsContextMenu);
//setContextMenuPolicy(Qt::DefaultContextMenu);
setToolTip(tr("Drag the clock with the left mouse button.\n"
"Use the right mouse button to open a context menu."));
setWindowTitle(tr("Shaped Analog Clock"));
}
//! [0]

//! [1]
void ShapedClock::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::LeftButton) {
//qDebug()<<"event->globalPos()"<<event->globalPos();

//qDebug()<<"frameGeometry().topLeft()"<<frameGeometry().topLeft();
dragPosition = event->globalPos() - frameGeometry().topLeft();
//qDebug()<<"dragPosition"<<dragPosition;
event->accept();
}
}
//! [1]

//! [2]
void ShapedClock::mouseMoveEvent(QMouseEvent *event)
{
if (event->buttons() & Qt::LeftButton) {
move(event->globalPos() - dragPosition);
event->accept();
}
}
//! [2]

//! [3]
void ShapedClock::paintEvent(QPaintEvent *)
{
static const QPoint hourHand[3] = {
QPoint(7, 8),
QPoint(-7, 8),
QPoint(0, -40)
};
static const QPoint minuteHand[3] = {
QPoint(7, 8),
QPoint(-7, 8),
QPoint(0, -70)
};

static const QPoint secondHand[3] = {
QPoint(7, 8),
QPoint(-7, 8),
QPoint(0, -100)
};

QColor hourColor(127, 0, 127);
QColor minuteColor(0, 127, 127, 191);
QColor secondColor(127, 127, 0, 191);

int w = width();
int h = height();
int side = qMin(width(), height());// QSize ShapedClock::sizeHint()
QTime time = QTime::currentTime();

QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
//painter.translate(width() / 2, height() / 2);
painter.translate(width() / 2, height() / 2);
painter.scale(side / 200.0, side / 200.0);
//painter.scale(side / 100.0, side / 100.0);

painter.setPen(Qt::NoPen);
//painter.setPen(Qt::DotLine);
painter.setBrush(hourColor);

painter.save();
painter.rotate(30.0 * ((time.hour() + time.minute() / 60.0)));
painter.drawConvexPolygon(hourHand, 3);
painter.restore();

painter.setPen(hourColor);

for (int i = 0; i < 12; ++i) {
painter.drawLine(88, 0, 96, 0);
painter.rotate(30.0);
}

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);

for (int j = 0; j < 60; ++j) {
if ((j % 5) != 0)
painter.drawLine(92, 0, 96, 0);
painter.rotate(6.0);
}

painter.setPen(Qt::NoPen);
painter.setBrush(secondColor);

painter.save();
painter.rotate(6.0 * (time.second()/* / 60.0*/));
painter.drawConvexPolygon(secondHand, 3);
painter.restore();
}
//! [3]

//! [4]
void ShapedClock::resizeEvent(QResizeEvent * /* event */)
{
int side = qMin(width(), height());
QRegion maskedRegion(width() / 2 - side / 2, height() / 2 - side / 2, side,
side, QRegion::Rectangle /*QRegion::Ellipse*/);
//QRegion maskedRegion(width() / 2 - side / 2, height() / 2 - side / 2, side / 2,
//side / 2, QRegion::Rectangle /*QRegion::Ellipse*/);
setMask(maskedRegion);
}
//! [4]

//! [5]
QSize ShapedClock::sizeHint() const
{
return QSize(clkAllSize, clkAllSize);
}
//! [5]

#include <QApplication>

#include "shapedclock.h"

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
ShapedClock clock;
clock.show();
return app.exec();
}