Reading mp3 from expansion file

Question

Reading mp3 file from expansion file

I have create and expansion file with name

"main.1.com.example.app.obb"

which contains and audio file name "about_eng.mp3"

Now the issue i have written the following code to read and play the mp3 file

    private final static String EXP_PATH = "/Android/obb/";

static String[] getAPKExpansionFiles(Context ctx, int mainVersion, int patchVersion) {
    String packageName = ctx.getPackageName();
    Vector<String> ret = new Vector<String>();
    if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
        // Build the full path to the app's expansion files
        File root = Environment.getExternalStorageDirectory();
        File expPath = new File(root.toString() + EXP_PATH + packageName);

        // Check that expansion file path exists
        if (expPath.exists()) {
            if ( mainVersion > 0 ) {
                String strMainPath = expPath + File.separator + "main." +
                        mainVersion + "." + packageName + ".obb";
                File main = new File(strMainPath);
                if ( main.isFile() ) {
                        ret.add(strMainPath);
                }
            }
            if ( patchVersion > 0 ) {
                String strPatchPath = expPath + File.separator + "patch." +
                        mainVersion + "." + packageName + ".obb";
                File main = new File(strPatchPath);
                if ( main.isFile() ) {
                        ret.add(strPatchPath);
                }
            }
        }
    }
    String[] retArray = new String[ret.size()];
    ret.toArray(retArray);
    return retArray;
}
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    // Get a ZipResourceFile representing a merger of both the main and patch files

    try {
        ZipResourceFile expansionFile = APKExpansionSupport.getAPKExpansionZipFile(this,1,1);
        if(expansionFile!=null){

            AssetFileDescriptor fd = expansionFile.getAssetFileDescriptor("about_eng.mp3");
                //or
            MediaPlayer mediaPlayer = new MediaPlayer();
            mediaPlayer.setDataSource( fd.getFileDescriptor(), 
                    fd.getStartOffset(),fd.getLength());
            mediaPlayer.prepare();
            mediaPlayer.start();

            }




    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    // Get an input stream for a known file inside the expansion file ZIPs


}

But it is always throwing exception at this line

 mediaPlayer.setDataSource( fd.getFileDescriptor(), 
                    fd.getStartOffset(),fd.getLength());
            mediaPlayer.prepare();

because the variable fd is null.

Can any body help me to solve this

Answer 1

i have googled and found that we shold have to make .zip with 0% (No compression) that is mention in http://developer.android.com/google/play/expansion-files.html

Tip: If you're packaging media files into a ZIP, you can use media playback calls on the files with offset and length controls (such as MediaPlayer.setDataSource() and SoundPool.load()) without the need to unpack your ZIP. In order for this to work, you must not perform additional compression on the media files when creating the ZIP packages. For example, when using the zip tool, you should use the -n option to specify the file suffixes that should not be compressed: zip -n .mp4;.ogg main_expansion media_files

so How to make 0% compression zip using winrar?

here see the compression method

so we should have to upload this zip in play store.

so you not need to use ZipHelper.java that is mentioned in other SO answer

just simply use

ZipResourceFile expansionFile=null;

            try {
                expansionFile = APKExpansionSupport.getAPKExpansionZipFile(getApplicationContext(),3,0);

                     AssetFileDescriptor fd = expansionFile.getAssetFileDescriptor("test.mp3");
                     MediaPlayer mPlayer = new MediaPlayer();
                     mPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
                     mPlayer.setDataSource(fd.getFileDescriptor(),fd.getStartOffset(),fd.getLength());
                     mPlayer.prepare();
                     mPlayer.start();

            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }