QT中窗口的渐变消失

void Widget::on_closeButton_clicked()
{
    /* 慢慢消失的效果 */
    QPropertyAnimation *animation = new QPropertyAnimation(this,"windowOpacity");
    animation->setDuration(1000);
    animation->setStartValue(1);
    animation->setEndValue(0);
    animation->start();
    connect(animation,SIGNAL(finished()),this,SLOT(close()));//效果显示完后关闭
}