Qt Qpushbutton设置背景色的问题

pushbutton->setStyleSheet("background-color:rgb(234,234,234)");

如下使用palette也无法设置背景色！

QPalette P=pushbutton->palette();

P.setColor(QPalette::Window,Qt::green);

P.setBrush(QPalette::Window,Qt::blue);

P.setColor(QPalette::ButtonText,Qt::red);

pushbutton->setPalette(P);

pushbutton->setBackgroundRole(QPalette::Button);

pushbutton->setAutoFillBackground(true);

http://blog.chinaunix.net/uid-25808509-id-1746294.html

http://www.cppblog.com/qianqian/archive/2010/07/25/121238.html

pushbutton=new QPushButton(tr("返回"),this);

QPalette P=pushbutton->palette();

P.setColor(QPalette::Window,Qt::green);

P.setBrush(QPalette::Window,Qt::blue);

P.setColor(QPalette::ButtonText,Qt::red);

pushbutton->setPalette(P);

pushbutton->setBackgroundRole(QPalette::Button);

pushbutton->setAutoFillBackground(true);

pushbutton->setStyleSheet("background-color:rgb(234,234,234)");

//    pushbutton->move(200,300);//设置子widget相对父widget中的位置

pushbutton->setGeometry(200,300,50,50);//设置子widget相对父widget中的位置及该widget的大小