Get duration of QMediaPlaylist object - qt

Question

I create a player for audiobooks - when you open a folder with mp3 file, whole list of them is added to playlist and List View. And i have a Label, which suppose to show duration of the whole book. But player->duration returns only a duration of current track, and if i go through the loop and do playlist->next() every step, player->duration returns 0. I know about Phonon and file metadata, but i need to do this without using it.

Answer 1

I am attaching a source code of a working project, you can use. When the player changes the file, the duration is changed and printed out. To loop within files, there is a need to wait till the decoder completes reading the media file. See the code below and the comments.
This is mainwindow.cpp
#include "mainwindow.h"
#include "mainwindow.h"
#include "ui_mainwindow.h"
bool done =false;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
player = new QMediaPlayer(this);
playlist = new QMediaPlaylist(player);
playlist->setPlaybackMode(QMediaPlaylist::Sequential);
player->setPlaylist(playlist);
connect(player, &QMediaPlayer::durationChanged, this, &MainWindow::on_durationchanged);
//connect(player,&QMediaPlayer::)
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::on_pushButton_clicked()
{
playlist->addMedia(QUrl::fromLocalFile("Ar_today.mp3"));
playlist->addMedia(QUrl::fromLocalFile("Ar_sunday.mp3"));
playlist->setCurrentIndex(0); //set the first file
while (done == false) //wait till the duration is read
{
QApplication::processEvents();
}
done = false; playlist->setCurrentIndex(1); //change to the second file
while (done == false) //wait till the duration is read
{
QApplication::processEvents();
} //this way you can loop through files
player->setVolume(80);
player->play();
qDebug() << player->errorString();
}
void MainWindow::on_pushButton_2_clicked()
{
player->stop();
}
void MainWindow::on_durationchanged(qint64 duration)
{
done = true;
qDebug() << "duration = " << player->duration();
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QMediaPlayer>
#include <QMediaPlaylist>
#include <QDebug>
extern bool done;
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();
private slots:
void on_pushButton_clicked();
void on_pushButton_2_clicked();
void on_durationchanged(qint64 duration);
private:
Ui::MainWindow *ui;
QMediaPlayer* player;
QMediaPlaylist* playlist;
};
#endif // MAINWINDOW_H
In the form, create 2 buttons, one called pushbutton to play and the other is pushButton_2 to stop