m_label = new QLabel();
ui->stackedWidget->addWidget(m_label);
ui->stackedWidget->setCurrentWidget(m_label); ui->stackedWidget->removeWidget(m_label);
m_label->setWindowFlags(Qt::Window);
m_label->setScaledContents(true);
m_label->showFullScreen();
m_label->setWindowFlags(Qt::Window);
这个语句很重要。