问如何处理QGraphicsItem的鼠标右键单击事件？

EN

class MyRect: public QObject, public QGraphicsItem
{     
        Q_OBJECT
        Q_INTERFACES(QGraphicsItem)
public:
        explicit MyRect(QObject *parent = 0);
        MyRect(QColor fillColor, float val, QString txt = "", bool isLeaf = false);
        int width, height;  
protected:
        virtual void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
        virtual void mousePressEvent(QGraphicsSceneMouseEvent *event);          
        virtual QRectF boundingRect() const;
        virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
};