关于qt:QgraphicsView橡皮筋拖动效果缩放行为

QgraphicsView rubberbanddrag effects zooming behavior

我被这种奇怪的行为困住了，如果我启用橡皮筋拖动，滚轮事件不再在鼠标下放大。它会缩放，但与鼠标位置无关。如果我禁用其他事件，则 wheelEvent 可以正常工作。

我有一个继承 QGraphicsView 的自定义类：

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class MyGraphics : public QGraphicsView{

public :
MyGraphics(QWidget *parent = NULL);

public slots:
void zoomIn() { scale(1.2, 1.2); }
void zoomOut() { scale(1 / 1.2, 1 / 1.2); }

protected :
QRubberBand *rubberBand;
QPoint origin;
QPointF InitialCenterPoint;
QPointF CurrentCenterPoint;
QPoint rubberBandOrigin;
bool rubberBandActive;
QPoint LastPanPoint;
int _numScheduledScalings;

//if I uncomment these three event handlers, the wheelevent doesnt zoom properly!

// virtual void mousePressEvent(QMouseEvent *event);
// virtual void mouseMoveEvent(QMouseEvent *event);
// virtual void mouseReleaseEvent(QMouseEvent *event);
virtual void wheelEvent(QWheelEvent *);
virtual void resizeEvent(QResizeEvent *event);

};

构造函数：

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MyGraphics::MyGraphics(QWidget *parent) : QGraphicsView(parent){
setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);

this->installEventFilter(this);
this->setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
this->setResizeAnchor( QGraphicsView::AnchorUnderMouse );
QGraphicsScene *graphScene = new QGraphicsScene(this);

this->setScene(graphScene);
QGraphicsItem* pEllipse = graphScene->addEllipse(0,100,50,50);
QGraphicsItem* pRect = graphScene->addRect(200,100,50,50);

pEllipse->setFlag(QGraphicsItem::ItemIsSelectable, true);
pRect->setFlag(QGraphicsItem::ItemIsSelectable, true);

setSceneRect(0, 0, 1000, 1000);
rubberBandOrigin = QPoint(0,0);
}

事件处理程序：

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void MyGraphics::wheelEvent(QWheelEvent *event){
if(event->delta() > 0){
//Zoom in
this->zoomIn();
} else {
this->zoomOut();
}

}

/*
void MyGraphics::mousePressEvent(QMouseEvent *event)
{
if (event->button() == Qt::MiddleButton) {
rubberBandOrigin = event->pos();
rubberBand = new QRubberBand(QRubberBand::Rectangle, this);
rubberBand->setGeometry(event->x(),event->y(),0, 0);
rubberBand->show();
rubberBandActive = true;
}
if(event->button() == Qt::LeftButton){
LastPanPoint = event->pos();
}

}

void MyGraphics::mouseMoveEvent(QMouseEvent *event)
{
if (event->buttons() == Qt::MiddleButton && rubberBandActive == true){
rubberBand->resize( event->x()-rubberBandOrigin.x(), event->y()-rubberBandOrigin.y() );
}
else{
if(!LastPanPoint.isNull()) {
//Get how much we panned
QGraphicsView * view = static_cast<QGraphicsView *>(this);

QPointF delta = view->mapToScene(LastPanPoint) - view->mapToScene(event->pos());
LastPanPoint = event->pos();
}
}
}

void MyGraphics::mouseReleaseEvent(QMouseEvent *event)
{
if (event->button() == Qt::MiddleButton){
QGraphicsView * view = static_cast<QGraphicsView *>(this);

QPoint rubberBandEnd = event->pos();

QRectF zoomRectInScene = QRectF(view->mapToScene(rubberBandOrigin), view->mapToScene(rubberBandEnd));
QPointF center = zoomRectInScene.center();

view->fitInView(zoomRectInScene, Qt::KeepAspectRatio);
rubberBandActive = false;
delete rubberBand;
}
else{
LastPanPoint = QPoint();
}
}
*/

知道我在哪里做错了或如何解决吗？