ListView repeating same JSON items on every Button click

Question

I have a ListView on my main Activity and a button to fetch the JSON.
If I repeat the Button click, the same JSON elements is added to the ListView.

How can I clear the ListView if I click the Button again ?

CustomListAdapter

public class CustomListAdapter extends BaseAdapter {
    private Activity activity;
    private LayoutInflater inflater;
    private List<Vehicle> vehicleItems;
    ImageLoader imageLoader = AppController.getInstance().getImageLoader();

    public CustomListAdapter(Activity activity, List<Vehicle> vehicleItems) {
        this.activity = activity;
        this.vehicleItems = vehicleItems;
    }

    @Override
    public int getCount() {
        return vehicleItems.size();
    }

    @Override
    public Object getItem(int location) {
        return vehicleItems.get(location);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        if (inflater == null)
            inflater = (LayoutInflater) activity
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null)
            convertView = inflater.inflate(R.layout.list_row, null);

        if (imageLoader == null)
            imageLoader = AppController.getInstance().getImageLoader();
        NetworkImageView thumbNail = (NetworkImageView) convertView
                .findViewById(R.id.thumbnail);
        TextView title = (TextView) convertView.findViewById(R.id.title);
        TextView rating = (TextView) convertView.findViewById(R.id.rating);
        TextView genre = (TextView) convertView.findViewById(R.id.genre);
        TextView year = (TextView) convertView.findViewById(R.id.releaseYear);

        // getting movie data for the row
        Vehicle m = vehicleItems.get(position);

        // thumbnail image
        thumbNail.setImageUrl(m.getThumbnailUrl(), imageLoader);

        // title
        title.setText(m.getTitle());

        // rating
        rating.setText("Rating: " + String.valueOf(m.getRating()));

        // genre
        String genreStr = "";
        for (String str : m.getGenre()) {
            genreStr += str + ", ";
        }
        genreStr = genreStr.length() > 0 ? genreStr.substring(0,
                genreStr.length() - 2) : genreStr;
        genre.setText(genreStr);

        // release year
        year.setText(String.valueOf(m.getYear()));

        return convertView;
    }
}

SearchActivity

public class SearchActivity extends Activity implements View.OnClickListener {

    // Log tag
    private static final String TAG = SearchActivity.class.getSimpleName();

    // Vehicles json url
    private static final String url = "https://api.myjson.com/bins/3u7ty";
    private SweetAlertDialog pDialog;
    private List<Vehicle> vehicleList = new ArrayList<Vehicle>();
    private ListView listView;
    private CustomListAdapter adapter;
    private Button buttonGet2;


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


        buttonGet2 = (Button) findViewById(R.id.buttonGet2);
        buttonGet2.setOnClickListener(this);



    }

    private void getData() {
        listView=(ListView) findViewById(R.id.list2);
        adapter=new CustomListAdapter(this,vehicleList);
        listView.setAdapter(adapter);
        final SweetAlertDialog pDialog = new SweetAlertDialog(this, SweetAlertDialog.PROGRESS_TYPE);
        pDialog.getProgressHelper().setBarColor(Color.parseColor("#A5DC86"));
        pDialog.setTitleText("Loading");
        pDialog.setCancelable(true);

        // Showing progress dialog before making http request
        pDialog.show();

        // changing action bar color
        getActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#1b1b1b")));

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

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

                                JSONObject obj = response.getJSONObject(i);
                                Vehicle vehicle = new Vehicle();
                                vehicle.setTitle(obj.getString("title"));
                                vehicle.setThumbnailUrl(obj.getString("image"));
                                vehicle.setRating(((Number) obj.get("rating"))
                                        .doubleValue());
                                vehicle.setYear(obj.getInt("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));
                                }
                                vehicle.setGenre(genre);

                                // adding vehicle to vehicles array
                                vehicleList.add(vehicle);

                            } 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());
                pDialog.dismissWithAnimation();

            }
        });

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

    }

    @Override
    public void onClick(View v) {
        getData();
    }
}

Answer 1

Along with clearing the data, just make that method only responsible for getting the data, not repeating initializing the adapter and list.

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

    buttonGet2 = (Button) findViewById(R.id.buttonGet2);
    buttonGet2.setOnClickListener(this);

    // Moved these lines
    listView = (ListView) findViewById(R.id.list2);
    adapter = new CustomListAdapter(this,vehicleList);
    listView.setAdapter(adapter);


}


private void getData() {

    vehicleList.clear();  // Added this

    final SweetAlertDialog pDialog = new SweetAlertDialog(this, SweetAlertDialog.PROGRESS_TYPE);
    pDialog.getProgressHelper().setBarColor(Color.parseColor("#A5DC86"));
    pDialog.setTitleText("Loading");
    pDialog.setCancelable(true);

Answer 2

You are adding the content of Json object to your vehicleList again and again. The vehicleList still holds the old values. Then you catch the values from the Json object again and add it again to the vehicleList. To get rid of this, clear the list:

    private void getData() {
    vehicleList.clear();
    listView=(ListView) findViewById(R.id.list2);
    adapter=new CustomListAdapter(this,vehicleList);

//rest of your code
}