How to properly set up a media player javafx

Question

I have created a media player method is javafx which is called upon startup (below is the media player). My problem is that this pauses whenever I interact with a scroll pane by dragging or by zooming the player pauses and does not start again. Why is this the case and how may I fix this(included full application if you would to try it).

Method(Live code)

    private static void MusicPlayer() {
    if(musicList.peek() == null)
    {
        return;
    }
    MediaPlayer mediaPlayer = new MediaPlayer(new Media(new File(musicList.poll()).toURI().toString()));
    mediaPlayer.setOnReady(() -> {
        mediaPlayer.play();
        mediaPlayer.setOnEndOfMedia(() -> {
            mediaPlayer.dispose();
            MusicPlayer();
        });
    });
}

Minimal

package minimalist;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
import java.util.stream.Collectors;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.StackPane;
import javafx.scene.media.Media;
import javafx.scene.media.MediaPlayer;
import javafx.stage.Stage;

public class Minimal extends Application{

    private static Queue<String> musicList = new LinkedList<String>();

    public static void main(String[] args) throws IOException {
        List<String> result = Files.find(Paths.get(".\\music"), 100,
                (p, a) -> p.toString().toLowerCase().endsWith(".mp3"))
                .map(path -> path.toString())
                .collect(Collectors.toList());
        for(int a = 0; a < result.size(); a++)
        {
            musicList.add(result.get(a));
        }
        MusicPlayer();
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        ScrollPane scrollpane = new ScrollPane();
        Image image = new Image("https://upload.wikimedia.org/wikipedia/commons/7/70/Kusatma_Zonaro.jpg");
        ImageView imageView = new ImageView(image);
        scrollpane.setContent(imageView);
        scrollpane.setPannable(true);
        Scene scene = new Scene(new StackPane(scrollpane));
        primaryStage.setScene(scene);
        primaryStage.setFullScreen(true);
        primaryStage.show();
    }

    private static void MusicPlayer() {
        if(musicList.peek() == null)
        {
            return;
        }
        MediaPlayer mediaPlayer = new MediaPlayer(new Media(new File(musicList.poll()).toURI().toString()));
        mediaPlayer.setOnReady(() -> {
            mediaPlayer.play();
            mediaPlayer.setOnEndOfMedia(() -> {
                mediaPlayer.dispose();
                MusicPlayer();
            });
        });
    }
}

Answer 1

This all seems to behave in something of a fragile manner.

I would not recommend launching the media player from the main method. The documentation is a bit lacking on threading policy for MediaPlayer, but since you are launching a regular JavaFX application it would seem sensible to follow the usual rules and only call methods on it from the JavaFX Application Thread. On my system, I was unable to get any music playing the way you had it set up.

I also had sporadic issues getting it to start playing after changing that; I guessed that maybe I was leaving system resources tied up after exiting, so I modified the code to ensure the player was disposed when the application ended. After both those changes, it behaved as expected. At no point though did I have any issues associated with user input; my guess is that these are caused by launching the media player from the main thread instead of from the FX Application Thread, and are probably system-dependent.

Here's the code that worked fine for me. I also cleaned up some of the redundancy in your code (iterating through Paths to convert them to Strings which you then convert back to Files so you can convert to a string representation of a URL seems somewhat circuitous; you also create a completely unnecessary list in that process, etc) and renamed things so that it abides by proper naming conventations):

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.LinkedList;
import java.util.Queue;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.StackPane;
import javafx.scene.media.Media;
import javafx.scene.media.MediaPlayer;
import javafx.stage.Stage;

public class Minimal extends Application{

    private Queue<Path> musicList = new LinkedList<>();

    private MediaPlayer mediaPlayer ;

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) throws Exception {

        // Everyone should have this album. Edit the path if your musical taste is poor.
        Files.find(Paths.get(System.getProperty("user.home"),"Music/iTunes/iTunes Media/Music/Thievery Corporation/Saudade/"), 100,
                (p, a) -> p.toString().toLowerCase().endsWith(".m4a"))
                .forEach(musicList::add);

        playMusic();

        ScrollPane scrollpane = new ScrollPane();
        Image image = new Image("https://upload.wikimedia.org/wikipedia/commons/7/70/Kusatma_Zonaro.jpg");
        ImageView imageView = new ImageView(image);
        scrollpane.setContent(imageView);
        scrollpane.setPannable(true);
        Scene scene = new Scene(new StackPane(scrollpane));
        primaryStage.setScene(scene);
        primaryStage.setFullScreen(true);
        primaryStage.show();

    }

    @Override
    public void stop() {
        if (mediaPlayer != null) {
            mediaPlayer.stop();
            mediaPlayer.dispose();
        }
    }

    private void playMusic() {
        if(musicList.peek() == null)
        {
            return;
        }
        mediaPlayer = new MediaPlayer(new Media(musicList.poll().toUri().toString()));
        mediaPlayer.setOnReady(() -> {
            mediaPlayer.play();
            mediaPlayer.setOnEndOfMedia(() -> {
                mediaPlayer.dispose();
                playMusic();
            });
        });

    }
}