aksd.java

public class LongPolling {
    private static final String BASE_URL = "http://serveraddress.com/";
    private static final String TAG = "LongPolling";
    private static LongPolling instance;
    private Context context;
    private PollingListener listener;
    private boolean poll;

    private LongPolling(final Context context) {
        this.context = context;
    }


    public static void init(final Context context) {
        if(instance == null) {
            instance = new LongPolling(context);
        }
    }
    public static LongPolling getInstance() {
        return instance;
    }

    public void setPollingListener(final PollingListener listener) {
        this.listener = listener;
    }

    public void startPolling() {
        poll = true;
        poll(context);
    }

    public void stopPolling() {
        poll = false;
    }

    private void poll(final Context context) {
        RequestQueue queue = Volley.newRequestQueue(context);

        final String url = BASE_URL + "events";
        Log.i(TAG, url);
        StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        ArrayList<Event> events = EventParser.parse(response);
                        if(listener != null) {
                            listener.onEventsReceived(events);
                        }
                        waitAndPoll();
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                if(error.networkResponse == null || error.networkResponse.statusCode != 708) { //Timeout
                    if(listener != null) {
                        listener.onPollingError();
                    }
                }
                waitAndPoll();
            }
        });

        queue.add(stringRequest);
    }

    private void waitAndPoll() {
        if(poll) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            poll(context);
        }
    }
}