Listview is doubled when returning to it

Question

I have five list views that are fragments in view pager tabs. When you click on the items in the list view it launches a new activity. But when I press the back-button to get back to the tabbed list view, the list view has doubled and if I open the activity and go back again it doubles again and it will keep doing that.I think the problem lies with this line of code

private List<Movie> movieList = new ArrayList<Movie>();

initiating on every return to the fragment however I am unsure on how to go about resolving it.

...

public class TabOneFragment extends ListFragment {

    private static final String TAG = AccommodationFragment.class.getSimpleName();

    // Movies json url
    private static final String url = "http://api.mywebsite.com/json/json.php";
    private ProgressDialog pDialog;
    private List<Movie> movieList = new ArrayList<Movie>();<----i think this is the cause???
    private ListView listView;
    private CustomListAdapter adapter;
    private View mheaderView;
//private TextView txtFragmentone;
public static TabOneFragment newInstance() {
    Bundle bundle = new Bundle();

    TabOneFragment fragment = new TabOneFragment();
    fragment.setArguments(bundle);

    return fragment;
}


    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {


        View rootView = inflater.inflate(R.layout.accommodation_fragment, container, false);
        rootView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT ));

        listView = (ListView) getActivity().findViewById(android.R.id.list);

        adapter = new CustomListAdapter(getActivity(), movieList);
        setListAdapter(adapter);



        mheaderView = inflater.inflate(R.layout.list_header, null);

        pDialog = new ProgressDialog(getActivity());
        // Showing progress dialog before making http request
        pDialog.setMessage("Loading...");
        pDialog.show();

        // Creating volley request obj
        JsonArrayRequest movieReq = new JsonArrayRequest(url,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.d(TAG, response.toString());
                        hidePDialog();

                        // Parsing json
                        for (int i = 0; i < response.length(); i++) {
                            try {

                                JSONObject obj = response.getJSONObject(i);
                                Movie movie = new Movie();
                                movie.setTitle(obj.getString("title"));
                                movie.setThumbnailUrl(obj.getString("image"));
                                movie.seturl(obj.getString("url"));
                                /*movie.setRating(((Number) obj.get("rating"))
                                        .doubleValue());*/
                                movie.setYear(obj.getString("releaseYear"));

                                // Genre is json array
                                JSONArray genreArry = obj.getJSONArray("genre");
                                ArrayList<String> genre = new ArrayList<String>();
                                for (int j = 0; j < genreArry.length(); j++) {
                                    genre.add((String) genreArry.get(j));
                                }
                                movie.setGenre(genre);

                                // adding movie to movies array
                                movieList.add(movie);

                            } catch (JSONException e) {
                                e.printStackTrace();
                            }

                        }

                        // notifying list adapter about data changes
                        // so that it renders the list view with updated data
                        adapter.notifyDataSetChanged();
                    }
                }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                hidePDialog();

            }
        });






        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(movieReq);




        return rootView;


    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        hidePDialog();
        setListAdapter(null);
    }

    private void hidePDialog() {
        if (pDialog != null) {
            pDialog.dismiss();
            pDialog = null;
        }
    }

...

Any help would be appreciated . Thanks.

Answer 1

The reason for doubling the data is your arraylist is not intialising everytime. you need to initialize it at oncreateview() method instead of globally initialised.

Answer 2

Can you check every time you click the back button from the activity, will the onCreate method of this Fragment calls.

If that is the case, before you run the for loop inside the onResponse method

 movieList.clear();

If this is not resolving the issue, the the issue is in the createView method in the adapter.

Answer 3

you have to clear you list before adding new data if you are adding all data again.

and better practice is to add only additional data in list rather than adding all data set again to list

you can clear list before start adding data like this.

 JsonArrayRequest movieReq = new JsonArrayRequest(url,
            new Response.Listener<JSONArray>() {
                @Override
                public void onResponse(JSONArray response) {
                    Log.d(TAG, response.toString());
                    hidePDialog();

                    movieList.clear();

                    // Parsing json
                    for (int i = 0; i < response.length(); i++) {
                        try {