QGraphicsView::scale 放大后QGraphicsScene上的item就全部消失了？

[wyjblue]

路过的高手帮下我，谢谢

[wyjblue]

为什么没人顶呢

[wyjblue]

代码如下：

void Myview::wheelEvent( QWheelEvent * event )
{

	setTransformationAnchor ( QGraphicsView::AnchorUnderMouse);
	double scaleFactor=1.15;
	//接收该事件
	if (event->delta()>0)
	scale(scaleFactor, scaleFactor);
	else
		scale(1.0 / scaleFactor, 1.0 / scaleFactor);
	m_transform=transform();
	return QGraphicsView::wheelEvent(event);
}