Problem with RecyclerView update

I have a RecyclerView on Android that downloads data with a PHP and Volley, and then displays a list of images with text. When I call another Activity that serves to filter searches for those objects in the DB, I press the apply flitro button, and return to the Main Activity again where the RecyclerView was. It is assumed that this should update and show only the new records with the filters applied, however, it shows as the first object the one that finds the filter applied, and then it continues showing the other objects that the application initially showed. I do not know if it's a problem updating the RecyclerView or not. This is the code of the method that fills the list with the filtered objects.

public static boolean filter=false;
private List<PlumImage> listPlums;

    //Creating Views
    private RecyclerView recyclerView;
    private RecyclerView.LayoutManager layoutManager;
    private RecyclerView.Adapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    context=this;

    //Initializing Views
    recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);

    recyclerView.setLayoutManager(layoutManager);

    listPlums = new ArrayList<>();
    requestQueue = Volley.newRequestQueue(this);

    //Toast.makeText(MainActivity.this, String.valueOf(filter), Toast.LENGTH_SHORT).show();
    if (filter==false){ //If filter is not enabled
        getData();
    }
    else{
        //Toast.makeText(MainActivity.this, String.valueOf(FiltersActivity.CATEGORY), Toast.LENGTH_SHORT).show();
        getDataFilter();
    }

    recyclerView.setOnScrollChangeListener(this);

    adapter = new PlumAdapter(listPlums, this);

    recyclerView.setAdapter(adapter);
 }

private void getDataFilter() {
    //Adding the method to the queue by calling the method getDataFromServer
    requestQueue.add(getDataFromServerFilter(requestCount));
    //Incrementing the request counter
    requestCount++;
}

private JsonArrayRequest getDataFromServerFilter(int requestCount) {
    //Initializing ProgressBar
    final ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressBar1);

    //Displaying Progressbar
    progressBar.setVisibility(View.VISIBLE);
    setProgressBarIndeterminateVisibility(true);

    //JsonArrayRequest of volley
    JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(AppConfig.FILTER_URL + String.valueOf(requestCount)+"&category="+FiltersActivity.CATEGORY,
            new Response.Listener<JSONArray>() {
                @Override
                public void onResponse(JSONArray response) {
                    //Calling method parseData to parse the json response
                    parseDataFilter(response);
                    //Hiding the progressbar
                    progressBar.setVisibility(View.GONE);
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    progressBar.setVisibility(View.GONE);
                    //If an error occurs that means end of the list has reached
                    Toast.makeText(MainActivity.this, "No More Items Available", Toast.LENGTH_SHORT).show();
                }
            });

    //Returning the request
    return jsonArrayRequest;
}

private void parseDataFilter(JSONArray array) {
    for (int i = 0; i < array.length(); i++) {
        //Creating the plum object
        PlumImage plum = new PlumImage();
        JSONObject json = null;
        try {
            //Getting json
            json = array.getJSONObject(i);

            //Adding data to the plum object
            plum.setPhoto(json.getString(AppConfig.TAG_IMAGE_URL));
            plum.setName(json.getString(AppConfig.TAG_NAME));
        } catch (JSONException e) {
            e.printStackTrace();
        }
        //Adding the plum object to the list
        listPlums.add(plum);
    }

    //Notifying the adapter that data has been added or changed
    recyclerView.destroyDrawingCache();
    adapter.notifyDataSetChanged();
}