Getting duration of music file in android

[MajidKamali]

Hi. I want to get duration of a music sound on android.
I connected a slot to durationChanged signal of QMediaPlayer but it shows the following error in android

W/dalvikvm(32228): No implementation found for native Lorg/qtproject/qt5/android/multimedia/QtAndroidMediaPlayer;.onStateChangedNative (IJ)V

my code:

    player = new QMediaPlayer(this);
    player->setMedia(QMediaContent(QUrl(media_file_name)));
    connect(player, &QMediaPlayer::durationChanged, [=](qint64 duration){
        qDebug() << "Duration:" << duration;
        media_duration = duration;
    });
    connect(player, &QMediaPlayer::stateChanged, [=](QMediaPlayer::State newState){
        if(newState == QMediaPlayer::PlayingState)
            setTilesEnabled(false);
        else
            setTilesEnabled(true);
    });

I commented second connect, but does not work either.

Qt 5.6.0 on Arch linux
Thanks