a.java

public class DetailFragment extends Fragment {
    // public List<Step> step;
    public ArrayList < Step > stepList;
    public Step currentStep;
    public ExoPlayer mExoPlayer;
    public SimpleExoPlayerView mPlayerView;
    public int position;
    public String videoURL;
    public Uri videoUri;
    public TextView textView;
    public String thumbnailURL;
    public String description;
    public Button nextButton;
    public DetailFragment() {
        // Required empty public constructor
    }
    public void showCurrentStep(Step currentStep) {
        videoURL = currentStep.getVideoURL();
        videoUri = Uri.parse(videoURL);
        initializePlayer(videoUri);
        Log.i("videoUrl", currentStep.getVideoURL());
        thumbnailURL = currentStep.getThumbnailURL();
        description = currentStep.getDescription();
    }
    @Override
    public View onCreateView(LayoutInflater inflater, final ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_detail, container, false);
        mPlayerView = (SimpleExoPlayerView) rootView.findViewById(R.id.video);
        nextButton = (Button) rootView.findViewById(R.id.next);
        textView = (TextView) rootView.findViewById(R.id.steps);
        textView.setText(description);
        // Inflate the layout for this fragment
        // Step steps = getArguments().getParcelable("Step");
        stepList = getArguments().getParcelableArrayList("Steps");
        position = getArguments().getInt("position");
        currentStep = stepList.get(position);
        nextButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                position++;
                currentStep = stepList.get(position);
                if (position >= stepList.size()) {
                    nextButton.setEnabled(true);
                    showCurrentStep(currentStep);
                    initializePlayer(videoUri);
                }
            }
        });
        return rootView;
    }
    public void initializePlayer(Uri videoURL) {
        if (mExoPlayer == null) {
            TrackSelector trackSelector = new DefaultTrackSelector();
            LoadControl loadControl = new DefaultLoadControl();
            mExoPlayer = ExoPlayerFactory.newSimpleInstance(getActivity(), trackSelector, loadControl);
            mPlayerView.setPlayer((SimpleExoPlayer) mExoPlayer);
            String userAgent = Util.getUserAgent(getContext(), "Baking App");
            MediaSource mediaSource = new ExtractorMediaSource(videoURL,
                new DefaultDataSourceFactory(getContext(), userAgent),
                new DefaultExtractorsFactory(), null, null);
            mExoPlayer.prepare(mediaSource);
            mExoPlayer.setPlayWhenReady(true);
        }
    }
    private void releasePlayer() {
        mExoPlayer.stop();
        mExoPlayer.release();
        mExoPlayer = null;
    }
}