Pagination with GSON (ANDROID)

I need to make a load on the end of the list, I have 20 items, when I get to the end, I need 20 more.

Currently my Fragment that loads the ads is as follows below.

        new AsyncHttpClient().get(Constantes.URL_WS_BASE + "anuncio/list", new JsonHttpResponseHandler() {
        @Override
        public void onSuccess(int statusCode, Header[] headers, JSONArray response) {
            if(response != null) {
                Type type = new TypeToken<List<Anuncio>>() {}.getType ();
                 anuncios = new Gson().fromJson(response.toString(), type);

                AnuncioRecyclerAdapter adapter = new AnuncioRecyclerAdapter(anuncios);
                rv.setAdapter(adapter);

            } else {
                Toast.makeText(getActivity(), "Houve um erro ao carregar a lista de anúncios.", Toast.LENGTH_LONG).show();
            }
            lytLoading.setVisibility(View.GONE);
        }

        @Override
        public void onFailure(int statusCode, Header[] headers, String responseString, Throwable throwable) {
            super.onFailure(statusCode, headers, responseString, throwable);
            Toast.makeText(getActivity(), "Falha: " + responseString, Toast.LENGTH_LONG).show();
        }
    });