请教各位一下,我用 setStyleSheet("QPushButton{border-style:flat;}" 
"QPushButton{border-image: url(:/UnitConvertor/Images/tab_temp_off.png);}" 
"QPushButton:pressed{border-image: url(:/UnitConvertor/Images/tab_temp_off.png);}" 
); 
给button设置了两张背景图片,但是当按下button时背景图片是换了,但button外围有一个“虚线框”,有没有办法去掉这个“虚线框”?