Nsryjdtyk

I'm kind of a newbie in Java programming and I'm trying to develope a class that can retrieve Media Tags (such as title, artist, ...) from imported MP3 files, this way I can store them in a personal MySQL database.

I've got this problem I've been trying to solve for a couple days now, but I couldn't really find a solution online.

This is my class:

public class FileImportClass extends Application {



    private static final Object obj = new Object();

    private static List<File> songList;

    private static ArrayList<String> title;

    private static ArrayList<String> artist;

    private static ArrayList<Integer> year;

    private static ArrayList<String> genre;

    private static ArrayList<String> duration;

    private static ArrayList<String> album;

    private static ArrayList<String> extension;

    private static ArrayList<String> size;

    private static ObservableMap<String, Object> songTags;



    public static void FileImport(Node node){

        title = new ArrayList<>();

        artist = new ArrayList<>();

        year = new ArrayList<>();

        genre = new ArrayList<>();

        duration = new ArrayList<>();

        album = new ArrayList<>();

        extension = new ArrayList<>();

        size = new ArrayList<>();



        FileChooser fileImport = new FileChooser();

        fileImport.setTitle("Importazione di File Audio");

        fileImport.getExtensionFilters().addAll(new ExtensionFilter("MP3 Files: ", "*.mp3"));

        Stage currentStage = (Stage) node.getScene().getWindow();

        songList = fileImport.showOpenMultipleDialog(currentStage);

        if (songList.size() > 50) {

            Alert alert = new Alert(Alert.AlertType.ERROR);

            alert.setTitle("Errore!");

            alert.setHeaderText("Errore nell'inserimento dei file audio!");

            alert.setContentText("È stato superato il massimo di 50 file audio importabili alla volta.");



            alert.showAndWait(); 

            return;

        }

        else{

            for(int i = 0; i < songList.size(); i++) {

                File file = songList.get(i);

                Media mediaFile = new Media(file.toURI().toString());

                double FILE_SIZE_D = file.length();

                int FILE_SIZE_I = (int) FILE_SIZE_D;

                int FILE_SIZE = FILE_SIZE_I / 1024;

                size.add(String.valueOf(FILE_SIZE) + " kB");



                final MediaPlayer mediaPlayer = new MediaPlayer(mediaFile);

                mediaPlayer.setOnReady(new Runnable(){

                    @Override

                    public void run() {

                        songTags = mediaPlayer.getMedia().getMetadata();

                        title.add(songTags.get("title").toString());

                        artist.add(songTags.get("artist").toString());



                        double DURATA_MINUTI_D = mediaFile.getDuration().toSeconds() / 60;

                        double DURATA_MINUTI_I = (int) DURATA_MINUTI_D;

                        double DURATA_SECONDI_D = (DURATA_MINUTI_D - DURATA_MINUTI_I) * 60;

                        double DURATA_SECONDI_I = (int) DURATA_SECONDI_D;



                        duration.add(String.valueOf(DURATA_MINUTI_I) + " min " + DURATA_SECONDI_I + " s");

                        if (songTags.get("genre") != null) {

                            genre.add(songTags.get("genre").toString());

                        }

                        else {

                            genre.add("Genere sconosciuto");

                        }



                        if (songTags.get("album") != null) {

                            album.add(songTags.get("album").toString());

                        }

                        else {

                            album.add("Album sconosciuto");

                        }

                        year.add((Integer) songTags.get("year"));

                        synchronized(obj){

                            obj.notify();

                        }

                    }

                });

            }

        }

        System.out.println(title);

        System.out.println(artist);

        System.out.println(genre);

        System.out.println(size);

        System.out.println(duration);

        System.out.println(album);

        System.out.println(year);

    }



    @Override

    public void start(Stage primaryStage) throws Exception {

        throw new UnsupportedOperationException("Not supported yet.");

    }

}

The problem is that, when I try to print the ArrayLists which contain the Tags, they aresult empty ("").
But if I try to print them from inside the mediaPlayer.setOnReady() function, then it works fine.

Is there anybody who could help me figure this out?

Thank you all in advance!

You're adding the tags inside 'MediaPlayer.setOnReady', which gets called when the status of the MediaPlayer object changes to READY. This doesn't happen immediately after you call the method but after some unknown time. What this means is your print statements are executed before the status change events, so the lists are still empty by then.

As Gnas says, there's a synchronicity issue here. You'll have to do something like this:

In your loop:

for(int i = 0; i < songList.size(); i++) {

    final int finalI = i;

    ...

At the end of the run() method:

if (finalI == songList.size() - 1) {

    System.out.println(title);

    System.out.println(artist);

    System.out.println(genre);

    System.out.println(size);

}