QGraphicView上如何实现鼠标画框
为了显示大图,并且加一些鼠标操作,我将Graphicview类控件升级为了Gwraphicview,并在Gwraphicview里面重新定义了mouseEvent,和paintEvent当鼠标点下时开始画框,当鼠标释放时画框结束,但是为什么提示QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1,画框也不显示?