自定义QMessageBox显示\按钮功能

QPushButton *okbtn = new QPushButton(QString::fromLocal8Bit("确定"));
QPushButton *cancelbtn = new QPushButton(QString::fromLocal8Bit("取消"));
QMessageBox *mymsgbox = new QMessageBox;
//mymsgbox->setIcon(QMessageBox::Warning);
mymsgbox->setWindowTitle(QString::fromLocal8Bit("提示"));
mymsgbox->setText(QString::fromLocal8Bit("确定退出吗？"));
mymsgbox->addButton(okbtn, QMessageBox::AcceptRole);
mymsgbox->addButton(cancelbtn, QMessageBox::RejectRole);
mymsgbox->setWindowFlags(Qt::widget);
//mymsgbox->setWindowFlags(Qt::FramelessWindowHint);
//mymsgbox->setWindowFlags(Qt::WindowSystemMenuHint );
mymsgbox->setWindowFlags(Qt::WindowStaysOnTopHint);
mymsgbox->show();
mymsgbox->exec();    //阻塞等待用户输入
if (mymsgbox->clickedButton()==okbtn)
{
    this->close();
}
    else{
}