1. 效果图

2. 源码实现

2.1 设置 QPushButton 默认样式

QPushButton{
	border:none;
	border-image: url(:/image/close.png);
}

2.2 主要实现源码

void MainWindow::on_switch_btn_clicked()
{
    if(m_switchisopen)
    {
        ui->switch_btn->setStyleSheet(
		            "QPushButton{\
		            border:none;\
		            border-image: url(:/image/close.png);\
		            }");
		            
        m_switchisopen = false;
    }
    else if(!m_switchisopen)
    {
        ui->switch_btn->setStyleSheet(
                    "QPushButton{\
                    border:none;\
                    border-image: url(:/image/open.png);\
                    }");

        m_switchisopen = true;
    }
}