C++ accessing object, QT - c++

Question

I'd appreciate it, when someone could help me. I am not used to C++. I am new to it.
My problem: I want to make an object "player" usable for another class. I don't get how to archive this.
main.cpp
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
mainwindow.h
#include <QMainWindow>
#include <QMediaPlayer>
#include <QDebug>
#include "Leap.h"
#include <leapmotionlistener.h>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
QMediaPlayer* player;
private slots:
....
private:
Ui::MainWindow *ui;
void initialize();
Controller controller;
LeapMotionListener leapMotionListener;
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QSound>
#include <iostream>
#include <QfileDialog>
using namespace std;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
player = new QMediaPlayer(this);
connect(player, &QMediaPlayer::positionChanged, this, &MainWindow::on_positionChanged);
connect(player, &QMediaPlayer::durationChanged, this, &MainWindow::on_durationChanged);
initialize();
}
QString path;
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::initialize(){
controller.addListener(leapMotionListener);
leapMotionListener.setPlayer(player);
controller.setPolicy(Leap::Controller::POLICY_BACKGROUND_FRAMES);
}
...
leapmotionlistener.h
#ifndef LEAPMOTIONLISTENER
#define LEAPMOTIONLISTENER
#include <iostream>
#include <cstring>
#include "Leap.h"
#include <QFile>
#include <QAudioOutput>
#include <QMediaPlayer>
using namespace Leap;
class LeapMotionListener : public Listener {
public:
LeapMotionListener();
void setPlayer(QMediaPlayer&);
//... some more methods
private:
QMediaPlayer player;
};
#endif // LEAPMOTIONLISTENER
leapmotionlistener.cpp
//calls the player object in one method like the following
player.stop();
My main questions are: What am I doing wrong while referencing and instantiating? And how can leapmotionlistener access the same player object (I want to influence the audio)?
I get the Error:
MusicPlayer\mainwindow.cpp:32: Error: C2664: 'void LeapMotionListener::setPlayer(QMediaPlayer &)' : converting from argument 1 'QMediaPlayer *' in 'QMediaPlayer &' not possible
This little project is downloadable for a quick view with the following link:
https://www.dropbox.com/s/igr7ywnvicdlxxd/MusicPlayer.zip?dl=0
Thanks in advance!

Answer 1

All you need to do is
leapMotionListener.setPlayer(*player);
An lvalue reference binds to an object, not to the pointer to the object. In order to get the object from a pointer to it, you need to dereference the pointer using the *.

Answer 2

Among other problems, the QMediaPlayer you're trying to pass to setPlayer is a pointer, not a reference to an object.
You can either instantiate your player object like this:
QMediaPlayer player;
Or you can change your setPlayer function signature to this:
void setPlayer(QMediaPlayer* mplayer);
If you update your function signature, you'll also need fix other function signatures and leave the ampersands out of your connect() statements when you're referencing the player.

Answer 3

the following worked now:
in MainWindow.h:
public:
QMediaPlayer* player;
in MainWindow.cpp:
player = new QMediaPlayer(this);
leapMotionListener.setPlayer(player);
controller.addListener(leapMotionListener);
in LeapMotionListener.h:
private:
QMediaPlayer *player;
public:
void setPlayer(QMediaPlayer *mplayer);
in LeapMotionListener.cpp:
LeapMotionListener::LeapMotionListener()
: player(0)
{}
void LeapMotionListener::setPlayer(QMediaPlayer *mplayer){
player = mplayer;
}