MusicManager.java

package tests.sound;

import java.util.ArrayList;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.audio.Music;
import com.badlogic.gdx.files.FileHandle;
import com.badlogic.gdx.utils.Disposable;
import com.olo.spam_the_spacebar.GameClass;

/**
 * A service that manages the background music.
 * <p>
 * Only one music may be playing at a given time.
 */
public class MusicManager implements Disposable {

    //available music files.
    public enum STSMusic{
        CAMPFIRE( "audio/music/campfire.ogg" ),
        HARDWIND( "audio/music/hardwind.ogg" ),
        RAIN_HARDWIND( "audio/music/rain&hardwind.ogg" ),
        TREES_WEAVING( "audio/music/trees_weaving.ogg" );

        private final String fileName;

        private STSMusic(String fileName){
            this.fileName = fileName;
        }

        public String getFileName(){
            return fileName;
        }
    }

    private ArrayList<Music> musicsBeingPlayed;
    private float volume = 1f;
    private boolean enabled = false;

    public static MusicManager instance;
    static{
        if(instance == null) new MusicManager();
    }

    public MusicManager(){
         if(instance != null){
            volume = instance.volume;
            enabled = instance.enabled;
            if(instance.isAnyMusicPlaying())
                instance.stop();
            else
                musicsBeingPlayed = instance.musicsBeingPlayed;
            instance.setEnabled(false);
            instance = null;
         }else{
             musicsBeingPlayed = new ArrayList<Music>();
         }

         instance = this;
    }

    //Plays the given music (starts the streaming).
    //If there is already a music being played it is stopped automatically.
    public void play(STSMusic music){
        if( ! enabled ) return;

        // stop any music being played
        Gdx.app.log( GameClass.LOG, "Playing music: " + music.name() );

        // start streaming the new music
        FileHandle musicFile = Gdx.files.internal( music.getFileName() );
        Music musicBeingPlayed = Gdx.audio.newMusic( musicFile );
        musicBeingPlayed.setVolume( volume );
        musicBeingPlayed.setLooping( true );
        musicBeingPlayed.play();
        musicsBeingPlayed.add(musicBeingPlayed);
    }

    public boolean isAnyMusicPlaying(){
        for(Music music : musicsBeingPlayed)
            if(music.isPlaying())
                return true;
        return false;
    }

    //Stops and disposes the current music being played, if any.
    public void stop(){
        if(isAnyMusicPlaying()){
            Gdx.app.log( GameClass.LOG, "Stopping current music" );
            for(Music music : musicsBeingPlayed){
                music.stop();
                music.dispose();
            }
            musicsBeingPlayed.clear();
        }
    }

    //Sets the music volume which must be inside the range [0,1].
    public void setVolume(float volume){
        Gdx.app.log( GameClass.LOG, "Adjusting music volume to: " + volume );

        // check and set the new volume
        if( volume < 0 || volume > 1f ) {
            throw new IllegalArgumentException( "The volume must be inside the range: [0,1]" );
        }
        this.volume = volume;

        // if there is a music being played, change its volume
        if(isAnyMusicPlaying()) {
           for(Music music : musicsBeingPlayed){
               music.setVolume(volume);
           }
        }
    }

    public void setEnabled(boolean enabled){
        this.enabled = enabled;

        // if the music is being deactivated, stop any music being played
        if(!enabled){
            stop();
        }
    }

    public void dispose(){
        Gdx.app.log( GameClass.LOG, "Disposing music manager" );
        stop();
    }

    public float getVolume(){
        return volume;
    }
}