The setItemWidget() doesn't work well with QGraphicsView

I create a QListWidget and call QListWidget::setItemWidget() to place widgets(such as QPushButton()) into the list widget.
And I add a lot of items to enable the vertical scrollbar, all the widget works well.
But once I put this composition widget into a QGraphicsView (via QGraphiscScene::addWidget()), the scrollbar won't works. The text of each item will scroll with the scrollbar, but the widgets(QPushButton()) won't scroll.