Primero que nada soy un novato y segundo, sé que existe una solución para "¿Cómo obtener canciones del álbum en Android?" pero eso es mediante el uso de cursor y MediaStore y yo hemos usado MediametadataRetriever y es totalmente diferente. No he usado hashmaps y todo ... así que se está poniendo un poco difícil ... por favor, ¿alguna solución para esto? hashmaps y mediastore ???

Aquí está el código que he usado para mostrar todas las canciones y sus artistas ..........

import java.io.File;
import java.io.FileFilter;
import java.io.FilenameFilter;
import java.io.Serializable;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.media.MediaMetadataRetriever;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.ListFragment;
import android.util.DisplayMetrics;
import android.util.TypedValue;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;


public class FragmentSongs extends  Fragment implements Serializable {
    AdapterView.AdapterContextMenuInfo info;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_song, container, false);
        ListView SngList = (ListView) view.findViewById(R.id.SongList);
        registerForContextMenu(SngList);
        File f=new File("/sdcard/Music");
        int j=0;int i=0;
        final ArrayList<SongDetails> Songinfo = getSongsFromDirectory(f);

        if (Songinfo.size()>0) {
            for( j=0; j<Songinfo.size();j++) {
                for ( i=j+1 ; i<Songinfo.size(); i++) { 
                    SongDetails a=Songinfo.get(i);
                    SongDetails b=Songinfo.get(j);
                    if (a.getSong().toLowerCase().compareTo(b.getSong().toLowerCase()) < 0) {
                        Songinfo.set(i,b );
                        Songinfo.set(j,a);
                    }
                 }
             }

             SngList.setOnItemClickListener(new OnItemClickListener() { 
                 public void onItemClick(AdapterView a, View v, int position, long id) {
                     Intent intent = new Intent(getActivity(), NowPlaying.class);
                     intent.putParcelableArrayListExtra("Data1",Songinfo);

                     intent.putExtra("Data2",position);
                     startActivity(intent);
                 }
             });

             SngList.setAdapter(new CustomAdapter(Songinfo));
             return view;
         } else {
             return null;
         }
   }

   public ArrayList<SongDetails> getSongsFromDirectory(File f) {
       MediaMetadataRetriever mmr = new MediaMetadataRetriever();
       ArrayList<SongDetails> songs = new ArrayList<SongDetails>();
       Bitmap bitmap2; 
       Bitmap bmp = BitmapFactory.decodeResource(getResources(), R.drawable.ab);

       float ht_px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 100, getResources().getDisplayMetrics());
       float wt_px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 100, getResources().getDisplayMetrics());

       Bitmap bitmap3 = Bitmap.createScaledBitmap(bmp, (int) ht_px, (int) wt_px, true);
       byte[] rawArt = null;
       Bitmap art;
       BitmapFactory.Options bfo=new BitmapFactory.Options();
       if (!f.exists() || !f.isDirectory()) {    
           return songs;
       }
       File[] files = f.listFiles(new Mp3Filter());
       for(int i=0; i<files.length; i++) { 
           if (files[i].isFile()) { 
               mmr.setDataSource(files[i].getPath());
               rawArt = mmr.getEmbeddedPicture();
               SongDetails detail=new SongDetails(); 
               if ( rawArt != null) {
                   bitmap2=BitmapFactory.decodeByteArray(rawArt, 0, rawArt.length, bfo);
                   bitmap2 = Bitmap.createScaledBitmap(bitmap2, (int) ht_px, (int) wt_px, true);
                   detail.setIcon(bitmap2);
               } else {  
                   detail.setIcon(bitmap3);
               }

               detail.setSong(files[i].getName()); 
               detail.setArtist(files[i].getName());
               detail.setArtist( mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_ARTIST)); 
               detail.setAlbum( mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_ALBUM)); 
               detail.setPath2( files[i].getPath()) ;
               songs.add(detail); 
            } else if (files[i].isDirectory()) { 
                songs.addAll(getSongsFromDirectory(files[i])); 
            } 

        }
        return songs;
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);      
        info = (AdapterContextMenuInfo) menuInfo;
        menu.add(Menu.NONE, v.getId(), 0, "Play");
        menu.add(Menu.NONE, v.getId(), 0, "Delete");
        menu.add(Menu.NONE, v.getId(), 0, "Queue Item");                  
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        if (item.getTitle() == "Play") {

        } else if (item.getTitle() == "Delete") {

        } else if (item.getTitle() == "Queue Item") {

        } else {
            return false;
        }
            return true;
    }
}

class Mp3Filter implements FileFilter {
    public boolean accept(File file) {
        return (file.isDirectory()||file.getName().endsWith(".mp3")|| file.getName().endsWith(".Mp3"));
    }
}