1、主窗体渐变

        QPropertyAnimation *animation =new QPropertyAnimation(this,"windowOpacity");animation->setDuration(500);animation->setStartValue(1);animation->setEndValue(0);animation->setEasingCurve(QEasingCurve::Linear);animation->start();connect(animation, SIGNAL(finished()), this, SLOT(showlogout()));

2、子控件渐变

    QGraphicsOpacityEffect *m_pGraphicsOpacityEffect =new QGraphicsOpacityEffect(ui->groupBox_login);m_pGraphicsOpacityEffect->setOpacity(1.0);ui->groupBox_login->setGraphicsEffect(m_pGraphicsOpacityEffect);QPropertyAnimation *animation =new QPropertyAnimation(m_pGraphicsOpacityEffect,"opacity",ui->groupBox_login);animation->setDuration(500);animation->setStartValue(1);animation->setEndValue(0);animation->setEasingCurve(QEasingCurve::Linear);animation->start();connect(animation, SIGNAL(finished()), this, SLOT(showlogout()));