Android - Volley JSON request to remote server only works correctly once

Question

I am developing an Android app where I need to fetch results from a MySQL database in a remote server. I have written some PHP scripts to query the database and output the results in JSON format.

The problem is that the request fetches expected results only for the first time. When I send the same request with different POST params, it returns the first result all over again. I modified the PHP script to attach the POST param in the JSON result and tried logging the POST param. It is also the same first param. If I uninstall the app from the device and re-install, again it returns the correct JSON only for the first time.

NOTE: When i run the same code with the same PHP scripts and same database on localhost (WAMPP), everything works perfect. I tried using the Google Chrome extension Postman to check the output from the remote server, it worked as expected. So, I can confirm that the problem is with my app/code.

Here's my CustomJSONObjectRequest class :

public class CustomJSONObjectRequest extends Request<JSONObject> {

private Listener<JSONObject> listener;
private Map<String, String> params;

public CustomJSONObjectRequest(String url, Map<String, String> params,
                     Listener<JSONObject> reponseListener, ErrorListener errorListener) {
    super(Method.GET, url, errorListener);
    this.listener = reponseListener;
    this.params = params;
}

public CustomJSONObjectRequest(int method, String url, Map<String, String> params,
                     Listener<JSONObject> reponseListener, ErrorListener errorListener) {
    super(method, url, errorListener);
    this.listener = reponseListener;
    this.params = params;
}

protected Map<String, String> getParams()
        throws com.android.volley.AuthFailureError {
    return params;
};

@Override
protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) {
    try {
        String jsonString = new String(response.data,
                HttpHeaderParser.parseCharset(response.headers));
        return Response.success(new JSONObject(jsonString),
                HttpHeaderParser.parseCacheHeaders(response));
    } catch (UnsupportedEncodingException e) {
        return Response.error(new ParseError(e));
    } catch (JSONException je) {
        return Response.error(new ParseError(je));
    }
}

@Override
protected void deliverResponse(JSONObject response) {
    listener.onResponse(response);
}
}

And this is how I am sending the request :

            String item_name = getIntent().getExtras().getString("item_name");
            String url = getString(R.string.remote_server)+"fetch-item-list.php";

            CustomJSONObjectRequest jsObjRequest = new CustomJSONObjectRequest(Request.Method.POST, url, null, new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {


                    try {
                        Log.d("item name from intent extra", item_name); //intent extra
                        Log.d("response", response.toString()); //json response
                        Log.d("item name from response", response.getString("item_name")); //post parameter. This and the intent extra should be same

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    Toast.makeText(getApplicationContext(), error.toString(), Toast.LENGTH_SHORT).show();
                }
            }) {
                @Override
                protected Map<String, String> getParams() throws AuthFailureError {
                    Map<String, String> params = new HashMap<>();

                    params.put("item_name", item_name);

                    return params;
                }

                @Override
                public Map<String, String> getHeaders() throws AuthFailureError {
                    Map<String, String> header = new HashMap<String, String>();
                    header.put("Content-Type", "application/json; charset=utf-8");
                    return header;
                }
            };



            MyVolleySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsObjRequest);

This is the logcat :

D/item name from intent extra: apple
D/Response: {"data":[{"item_discount":"0.00","item_price":"50.00","unique_id":"181................
D/item name from response: orange

Answer 1

I think I found the solution

Looks like the JSON response was getting cached, so the response for the first request got cached and the next requests were never sent to the server. The cached JSON response was returned for every other requests.

All I had to do was disable caching. I added the line jsObjRequest.setShouldCache(false); before adding it to the request queue.

jsObjRequest.setShouldCache(false);
MyVolleySingleton.getInstance(getApplicationContext()).addToRequestQueue(jsObjRequest);

Thanks to this question.

But I still do not get it why it worked on localhost without this setting.