关于QGraphicsObject类的一个诡异问题

[a835941119]

我自写了一个类ClockHand,父类是QGraphicsObject。
paint（）函数里画了两个矩形，但是它们的形状却出乎意料，请大神指教！
clockhand.h

#ifndef CLOCKHAND_H
#define CLOCKHAND_H

#include <QGraphicsObject>

class ClockHand : public QGraphicsObject
{
public:
    explicit ClockHand();
public:
    QRectF boundingRect() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
protected:
    void dragEnterEvent(QGraphicsSceneDragDropEvent *event);
    void dragLeaveEvent(QGraphicsSceneDragDropEvent *event);
    void dropEvent(QGraphicsSceneDragDropEvent *event);
private:
    QColor color;
    bool dropOver;
    //QPoint *shape;
};

#endif // CLOCKHAND_H

clockhand.cpp

#include "clockhand.h"
#include <QtGui>


ClockHand::ClockHand() : color(Qt::white),dropOver(false)
{
    setAcceptDrops(true);
}

QRectF ClockHand::boundingRect() const
{
    return QRectF(-21,-66,21,6);
}

void ClockHand::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    Q_UNUSED(option);
    Q_UNUSED(widget);
    painter->setRenderHint(QPainter::Antialiasing);
    painter->setBrush(dropOver ? color.light(140) : color);
    painter->drawRect(-9,-9,25,25);
    painter->drawRect(-20,-65,20,5);
}

void ClockHand::dragEnterEvent(QGraphicsSceneDragDropEvent *event)
{
    if(event->mimeData()->hasColor())
    {
        event->setAccepted(true);
        dropOver = true;
        update();
    }
    else
    {
        event->setAccepted(false);
    }
}

void ClockHand::dragLeaveEvent(QGraphicsSceneDragDropEvent *event)
{
    Q_UNUSED(event);
    dropOver = false;
    update();
}

void ClockHand::dropEvent(QGraphicsSceneDragDropEvent *event)
{
    dropOver = false;
    if(event->mimeData()->hasColor())
        color = qvariant_cast<QColor>(event->mimeData()->colorData());

    update();
}

main.cpp

#include "coloritem.h"
#include <QApplication>
#include "coloritem.h"
#include "clock.h"
#include <QtGui>
#include "clockhand.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    qsrand(QTime(0,0,0).secsTo(QTime::currentTime()));

    QGraphicsScene *scene  = new QGraphicsScene(-500,-500,1000,1000);
//    ColorItem *c1=new ColorItem;
//    ColorItem *c2=new ColorItem;
//    c1->setPos(60,40);
//    c2->setPos(80,40);
//    Clock *clock = new Clock;
//    clock->setPos(200,200);
//    QPoint secPolygon[4] = {QPoint(0,5),QPoint(-20,-15),QPoint(0,-65),QPoint(20,-15)};
    ClockHand *secHand = new ClockHand();
    secHand->setPos(-100,0);
//    scene->addItem(c1);
//    scene->addItem(c2);
//    scene->addItem(clock);
    scene->addItem(secHand);

    QGraphicsView view(scene);
    view.setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);
    view.show();

    return a.exec();
}

结果：
大的矩形是：painter->drawRect(-9,-9,25,25);
小的矩形是：painter->drawRect(-20,-65,20,5);
为什么会这样？

[yangsh3002]

很正常啊，诡异在哪儿

[a835941119]

引用 1 楼 yangsh3002 的回复:

很正常啊，诡异在哪儿

按理来说大的矩形不对啊，不应该这么小。

[a835941119]

引用 1 楼 yangsh3002 的回复:

很正常啊，诡异在哪儿

我脑子有包，自己理解错了，以为drawRect的后两个参数是右下角坐标，其实是长和宽。 谢谢。结贴。