QPushButton样式表顺序问题

QPushButton {    background-color:transparent;    background-image: url(:/img/close_normal.png);}QPushButton:hover{    background-color:transparent;    background-image: url(:/img/close_hover.png);}QPushButton:pressed{    background-color:transparent;    background-image: url(:/img/close_press.png);}

样式顺序为normal、hover、pressed，如果将pressed放在hover前面，样式不能正常显示。