How to fetch album and artist info. I wanna know what does this code do?

Could someone please explain this to me line by line?I don't want to just copy paste stuffs without having proper knowledge about what i am actually doing

Uri sArtworkUri = Uri.parse("content://media/external/audio/albumart");
Uri uri = ContentUris.withAppendedId(sArtworkUri, album_id);
ContentResolver res = context.getContentResolver();
InputStream in = res.openInputStream(uri);
Bitmap artwork = BitmapFactory.decodeStream(in);

i am trying to use the code above in the code below to fetch music artists and album etc............................

.................................... ...................... ...........................

public ArrayList<SongDetails> getSongsFromDirectory(File f)
        {MediaMetadataRetriever mmr = new MediaMetadataRetriever();
            ArrayList<SongDetails> songs = new ArrayList<SongDetails>();
            if (!f.exists() || !f.isDirectory()) 

            {    
                return songs;
            }
            File[] files = f.listFiles(new Mp3Filter());
            for(int i=0; i<files.length; i++) 
            { 
                Uri uri = Uri.fromFile(files[i]);
                //mmr.setDataSource(null, uri);

            if (files[i].isFile()){ 
            SongDetails detail=new SongDetails(); 
            detail.setIcon(R.drawable.ic_launcher); 

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

            }

            return songs;



    } }

Solution

Uri sArtworkUri = Uri.parse("content://media/external/audio/albumart");

This line will, "Creates a Uri which parses the given encoded URI string." (from http://developer.android.com/reference/android/net/Uri.html) A URI is a uniform resource identifier which is unique indentifier for a web resource.

Uri uri = ContentUris.withAppendedId(sArtworkUri, album_id);

ContentUris is a, "Utility methods useful for working with Uri objects that use the "content" (content://) scheme." (http://developer.android.com/reference/android/content/ContentUris.html) with appender ID appends the album_id to the end of the passed in URI. Essentially you're making a new URI to point directly to the album.

ContentResolver res = context.getContentResolver();

Provides access to content model (http://developer.android.com/reference/android/content/ContentResolver.html)

InputStream in = res.openInputStream(uri);

This gives you access to content at URI via an InputStream. InputStreams allow you to read in data. http://developer.android.com/reference/java/io/InputStream.html

 Bitmap artwork = BitmapFactory.decodeStream(in);

Lastly this method will load the image at the URI from the input stream. So you now have the image available to you in memory.