public class FotoActivity extends Activity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_filter);

        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new FotoFragment())
                    .commit();
        }
    }


    public static class FotoFragment extends AbsListViewBaseFragment implements AbsListView.OnScrollListener {

        private static final String CLIENT_ID = "7f38ead5152e46f1a42284c2d84b0862";
        private static final String API_REQUEST = "cat";
        private static final String API_URL = "https://api.instagram.com/v1";

        static String downloadJsonUrl = API_URL + "/tags/" + API_REQUEST + "/media/recent?client_id=" + CLIENT_ID;

        private ImageAdapter picAdapter;

        ArrayList<String> picUrls = new ArrayList<String>();

        GetImages getInstagramImages;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            picAdapter = new ImageAdapter();

            getInstagramImages = new GetImages();
            getInstagramImages.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);

        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fr_image_grid, container, false);
            listView = (GridView) rootView.findViewById(R.id.grid);
            ((GridView) listView).setAdapter(picAdapter);
            listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                }
            });

            listView.setOnScrollListener(this);

            return rootView;
        }

        @Override
        public void onScrollStateChanged(AbsListView absListView, int i) {

        }

        @Override
        public void onScroll(AbsListView absListView, int firstVisible, int visibleCount, int totalCount) {
            boolean loadMore = firstVisible + visibleCount >= totalCount;

            if (loadMore == true && getInstagramImages.getStatus() == AsyncTask.Status.FINISHED) {
                getInstagramImages = new GetImages();
                getInstagramImages.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
            }
        }


        protected class GetImages extends AsyncTask<Void, Void, ArrayList> {

            @Override
            protected ArrayList doInBackground(Void... voids) {
                try {
                    picUrls = parseJson();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (JSONException e) {
                    e.printStackTrace();
                }
                return picUrls;
            }

            @Override
            protected void onPostExecute(ArrayList result) {
                super.onPostExecute(result);
                picAdapter.notifyDataSetChanged();
            }
        }


        private InputStream downloadJSON(String stringUrl) throws IOException {
            URL url = new URL(stringUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.setDoInput(true);
            connection.connect();
            return connection.getInputStream();
        }


        private ArrayList parseJson() throws IOException, JSONException {
            InputStream inputStream = downloadJSON(downloadJsonUrl);
            JSONObject jsonObject = (JSONObject) new JSONTokener(responseJSON).nextValue();
            JSONArray jsonArray = jsonObject.getJSONArray("data");
            for(int i = 0; i < jsonArray.length(); i ++){
                JSONObject imageJsonObject = jsonArray.getJSONObject(i).getJSONObject("images").getJSONObject("standard_resolution");
                picUrls.add(imageJsonObject.getString("url"));
            }
            downloadJsonUrl = jsonObject.getJSONObject("pagination").getString("next_url");

            return picUrls;
        }

}