I've found a way, as follows: 🙂 Problem Solved!
customwidget = new QWidget();
customwidget ->setAttribute( Qt::WA_TranslucentBackground, true );
widgetproxy = m_mapGraphicsView->scene()->addWidget(customwidget);
connect(&m_map,SIGNAL(extentChanged()),this,SLOT(extentChangedStatus()));
connect(&m_map,SIGNAL(mouseWheel(QWheelEvent)),this,SLOT(mouseWheelStatus()));
connect(&m_map,SIGNAL(mouseMove(QMouseEvent)),this,SLOT(mouseMoveStatus()));
connect(&m_map,SIGNAL(mouseDoubleClick(QMouseEvent)),this,SLOT(mouseWheelStatus()));
////////////////////////////////////////////////////////////////////////////
void MainWindow::extentChangedStatus()
{
    if(mouseWheelTimer.isActive())
        mouseWheelTimer.stop();
    widgetproxy->setPos(m_map.toScreenPoint(point).x()-(widgetproxy->geometry().width()/2),m_map.toScreenPoint(point).y()-(widgetproxy->geometry().height()/2));
    if(widgetproxy->opacity() == 0.0)
    {
        QPropertyAnimation *animation = new QPropertyAnimation(widgetproxy, "opacity");
        animation->setDuration(200);
        animation->setStartValue(0);
        animation->setEndValue(1);
        animation->start(QAbstractAnimation::DeleteWhenStopped);
    }
}
////////////////////////////////////////////////////////////////////////////
void MainWindow::mouseWheelStatus()
{
    QPropertyAnimation *animation = new QPropertyAnimation(widgetproxy, "opacity");
    animation->setDuration(100);
    animation->setStartValue(1);
    animation->setEndValue(0);
    animation->start(QAbstractAnimation::DeleteWhenStopped);
    mouseWheelTimer.start();
}
////////////////////////////////////////////////////////////////////////////
void MainWindow::mouseMoveStatus()
{
    widgetproxy->setPos(m_map.toScreenPoint(point).x()-(widgetproxy->geometry().width()/2),m_map.toScreenPoint(point).y()-(widgetproxy->geometry().height()/2));
}
////////////////////////////////////////////////////////////////////////////
void MainWindow::mouseWheelStatus()
{
    QPropertyAnimation *animation = new QPropertyAnimation(widgetproxy, "opacity");
    animation->setDuration(100);
    animation->setStartValue(1);
    animation->setEndValue(0);
    animation->start(QAbstractAnimation::DeleteWhenStopped);
    mouseWheelTimer.start();
}