How do I make a working volume slider in Qt?

Question

I'm trying to make a volume slider that changes the volume of the player in QT but I can't get it to work.

This is a picture of my music player. Currently, when I slide the volume slider while music is playing, the volume does not change/update to the value of the slider.

These are snipets of the code I'm using for the volumeslider:

volumeSlider = new QSlider(Qt::Horizontal, this);
volumeSlider->setRange(0, 100);
volumeSlider->setFixedWidth(100);
volumeSlider->setValue(100);
player = new QMediaPlayer;

..

connect(volumeSlider, SIGNAL(valueChanged(int)), this, SIGNAL(volumeChanged(int)));
connect(volumeSlider, SIGNAL(volumeChanged(int)), player, SLOT(setVolume(int)));

..

    int MainWindow::volume() const
{
    return volumeSlider->value();
}


void MainWindow::setVolume(int volume)
{
    player->setVolume(volume);
}

Answer 1

Eh...I mean just one line

connect(volumeSlider, SIGNAL(valueChanged(int)),player, SLOT(setVolume(int)));

and that's all you need to make it work.

---

Your original code:

connect(volumeSlider, SIGNAL(valueChanged(int)), this, SIGNAL(volumeChanged(int)));
connect(volumeSlider, SIGNAL(volumeChanged(int)), player, SLOT(setVolume(int)));  
      //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Error here

is wrong because there is no volumeChanged(int) signal in QSlider , and there should be some notification about failed connection from Qt Creator as you compiled the code (shown in the console of Qt Creator).

I guess the volumeChanged(int) is a custom signal defined in the main widget, and if you change the original code to

connect(volumeSlider, SIGNAL(valueChanged(int)), this, SIGNAL(volumeChanged(int)));
connect(this, SIGNAL(volumeChanged(int)), player, SLOT(setVolume(int)));
     // ^^^^

and it should work because you connect A to B and then connect B to C, but it's verbose. Hence I asked you why not just connect A to C.

As for your last modification:

connect(volumeSlider, SIGNAL(valueChanged(int)), this, SIGNAL(volumeChanged(int))); // Does nothing
connect(volumeSlider, SIGNAL(valueChanged(int)), player, SLOT(setVolume(int)));

It's like connect A to B, and connect A to C but only the connection of A to C works (mentioned above). The first connection is not necessary (since B is a SIGNAL )

Answer 2

I'm dumb, it was as simple as changing:

connect(volumeSlider, SIGNAL(valueChanged(int)), this, SIGNAL(volumeChanged(int)));
connect(volumeSlider, SIGNAL(volumeChanged(int)), player, SLOT(setVolume(int)));

to

connect(volumeSlider, SIGNAL(valueChanged(int)), this, SIGNAL(volumeChanged(int)));
connect(volumeSlider, SIGNAL(valueChanged(int)), player, SLOT(setVolume(int)));

Thank you Tay2510: "Why not just connect valueChanged(int) to setVolume(int)? – Tay2510"