Qt子类化的图形场景不允许我选择/聚焦到它上面的图形项目

我已经将我自己的qgraphicsview子类化了，因为我想在点击时从带有位置的场景发送信号，在这个场景中还有我的子类图形itms，它们是可选择和可聚焦的。问题是，当我在场景中实现自己的mousepressed/mousemoved/mousereleased事件处理程序时，我突然无法选择场景中的任何内容。

以下是我对图形场景的实现：

/////////////////////HEADER//////////////
#include <QGraphicsScene>
class myGraphicsScene : public QGraphicsScene
{
    Q_OBJECT
public:
   explicit myGraphicsScene(QObject * parent = 0);
   explicit myGraphicsScene(qreal x, qreal y, qreal width, qreal height, QObject * parent = 0);
signals:
   void mouseReleased(QPointF pos);
   void mousePressed(QPointF pos);
   void mouseMoved(QPointF pos);
   void mouseDoubleClicked(QPointF pos);
protected:
   void mouseDoubleClickEvent (QGraphicsSceneMouseEvent * event);
   void mousePressEvent(QGraphicsSceneMouseEvent * event);
   void mouseMoveEvent(QGraphicsSceneMouseEvent * event);
   void mouseReleaseEvent(QGraphicsSceneMouseEvent * event);

 ////////////////////CPP//////////////////////
 #include <QGraphicsSceneMouseEvent>

 myGraphicsScene::myGraphicsScene(QObject *parent) : QGraphicsScene(parent)
 {
 }
 myGraphicsScene::myGraphicsScene(qreal x, qreal y, qreal width, qreal height, QObject *parent)
    : QGraphicsScene( x, y, width, height, parent )
 {
 }
 void myGraphicsScene::mouseDoubleClickEvent ( QGraphicsSceneMouseEvent *event )
 {
     QGraphicsScene::mouseDoubleClickEvent ( event );
     emit mouseDoubleClicked ( event->scenePos () );
 }
 void myGraphicsScene::mousePressEvent (QGraphicsSceneMouseEvent *event)
 {
    QGraphicsScene::mousePressEvent ( event );
    emit mousePressed ( event->scenePos () );
 }
 void myGraphicsScene::mouseMoveEvent (QGraphicsSceneMouseEvent *event)
 {
    QGraphicsScene::mouseMoveEvent ( event );
    emit mouseMoved ( event->scenePos () );
 }
 void myGraphicsScene::mouseReleaseEvent (QGraphicsSceneMouseEvent *event)
 {
    QGraphicsScene::mousePressEvent ( event );
    emit mouseReleased ( event->scenePos () );
 }

哪个事件实现是错误的

附言：当我评论掉mousePressed/moved/released的实现时，它就像魅力一样。