QMediaPlayer::position() return zero

I was trying to get position of current media like that:

player->setNotifyInterval(500);

connect(Player::player, &QMediaPlayer::positionChanged, this, &Player::ChangedPosition);

void Player::ChangedPosition(qint64 position)
{
    Player::currentPosition = position; //qint64 variable
    //currentPosition still 0

    qDebug() << "current position: " << currentPosition;

    return;
}

I was trying to make like that (because doc of Qt does not say about this slot QMediaPlayer::setPosition)

connect(Player::player, &QMediaPlayer::positionChanged, this, &QMediaPlayer::setPosition);

I have two class (Playlist and Player):

playlistmanager - object of Playlist class

playermanager - object of Player class

set playlist and play it:

//set current media
playlistmanager->GetCurrentPlayList()->setCurrentIndex(newIndex);
//play this media
playermanager->play();
//set current position
playermanager->SetPositionOfTrack(playermanager->GetPositionOfTrack());

After this code media is playing but from the beginning

Here two methods of Player class:

qint64 Player::GetPositionOfTrack()
{
    return currentPosition; //qint64 variable in class
}

void Player::SetPositionOfTrack(const qint64 position)
{
    player->setPosition(position);

    return;
}

So, How can I get current position of current media?

need to use this pointer if I create object like that: player = new QMediaPlayer(this);. Wrong example:

connect(Player::player, &QMediaPlayer::positionChanged, this, &QMediaPlayer::setPosition);

Constructor of the correct class:

    Player::Player()
    {
        try
        {
            player = new QMediaPlayer(this);
        }
        catch(std::bad_alloc &exp)
        {
            #ifndef Q_DEBUG
            qCritical() << "Exception caught: " << exp.std::bad_alloc::what();
            #endif
            abort();
        }
        catch(...)
        {
            #ifndef Q_DEBUG
            qCritical() << "Some exception caught";
            #endif
            abort();
        }
    
        player->setNotifyInterval(500);
        
        connect(this, &QMediaPlayer::positionChanged, this, &Player::ChangedPosition);
    
        return;
    }