Sample Source for vtt in ExoPlayer

HTTPSampleSource.java

package vcuplayer;

import android.media.MediaPlayer;
import android.os.AsyncTask;
import android.util.Log;

import com.google.android.exoplayer.MediaFormat;
import com.google.android.exoplayer.MediaFormatHolder;
import com.google.android.exoplayer.SampleHolder;
import com.google.android.exoplayer.SampleSource;
import com.google.android.exoplayer.TrackRenderer;
import com.google.android.exoplayer.util.Assertions;
import com.google.android.exoplayer.util.MimeTypes;


import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.nio.ByteBuffer;

/**
 * Created by aguru on 01/01/16.
 */
public class HttpSampleSource extends AsyncTask<Void, Void, Void> implements SampleSource, SampleSource.SampleSourceReader {

    private ByteBuffer byteBuffer;
    private int byteBufferSize;
    private URL url;
    private String mimeType;
    private MediaPlayer.TrackInfo trackInfo;
    private boolean readNeeded = true;

    HttpSampleSource(URL url, String mimeType){
      this.url = url;
      this.mimeType = mimeType;
    }

    @Override
    protected Void doInBackground(Void... params) {
        try
        {
            URLConnection conn = url.openConnection();
            InputStream inputStream = conn.getInputStream();

            ByteArrayOutputStream byteArrayOS = new ByteArrayOutputStream();

            byte[] buffer = new byte[1024];
            int len;
            while ((len = inputStream.read(buffer)) != -1 && !isCancelled())
            {
                byteBufferSize += len;
                byteArrayOS.write(buffer, 0, len);
            }
            byteBuffer = ByteBuffer.wrap(byteArrayOS.toByteArray());
        } catch (Exception e)
        {
            Log.d("VCU Log", e.getMessage());
        }
        return null;
    }

    @Override
    public SampleSourceReader register() {
        return null;
    }

    @Override
    public void maybeThrowError() throws IOException {

    }

    @Override
    public boolean prepare(long positionUs) {
        if (getStatus() == AsyncTask.Status.PENDING) {
            execute();
        }

        return true;
    }

    @Override
    public int getTrackCount() {
        return 1;
    }

    @Override
    public MediaFormat getFormat(int track) {

        return  MediaFormat.createTextFormat(Integer.toString(track), mimeType,
                MediaFormat.NO_VALUE, TrackRenderer.MATCH_LONGEST_US, "en");
    }

    @Override
    public void enable(int track, long positionUs) {
        readNeeded = true;
    }

    @Override
    public boolean continueBuffering(int track, long positionUs) {
        return false;
    }

    @Override
    public int readData(int track, long positionUs, MediaFormatHolder formatHolder,
                        SampleHolder sampleHolder, boolean onlyReadDiscontinuity) {

        if (byteBuffer == null)
        {
            return NOTHING_READ;
        }

        if (sampleHolder != null && readNeeded){
            sampleHolder.size = byteBufferSize;
            sampleHolder.data = byteBuffer;
            readNeeded = false;
            return SAMPLE_READ;
        }

        return END_OF_STREAM;
    }

    @Override
    public void seekToUs(long positionUs) {
        //return positionUs;
    }

    @Override
    public long getBufferedPositionUs() {
        return TrackRenderer.END_OF_TRACK_US;
    }

    @Override
    public void disable(int track) {

    }

    @Override
    public void release() {

    }
}