Getting Android Volley null error after calling specific php functions, other functions work fine

Question

I've got an android application which communicates with a webserver using PHP and Volley. My app sends a Post request to a Listener.php file on my webserver and chooses different functions in a Functions.php. The problem is: some functions lead to a volley null error although the code is executed. Theres no error in apache erroglog and I can see the data change in my database. But I want to process a response in my app which is not possible when I get this error. The webserver is running on my raspberry pi now and I get this error all the time when calling specific functions, other functions are working as expected. When I test the same code on Windows its working fine (although these null errors are happening too from time to time at the same functions). I really hope theres someone to put me in the right direction, I have no idea how to proceed with that kind of problem..

Java/Volley Post

  public static void importNewMedia(final Context context) {


    final String TAG = "importMedia";
    String tag_string_req = "admin_control";
    StringRequest strReq = new StringRequest(com.android.volley.Request.Method.POST,
            AppConfig.URL_SERVER, new Response.Listener<String>() {



        @Override
        public void onResponse(String response) {
            Log.d(TAG, response.toString());
            try {
                JSONObject jObj = new JSONObject(response);
                boolean error = jObj.getBoolean("error");
                if (!error) {

                    Toast.makeText(context, "Database has been updated!", Toast.LENGTH_SHORT).show();

                } else {

                    Toast.makeText(context,
                            "Database has not been updated!", Toast.LENGTH_SHORT).show();

                }
            } catch (JSONException e) {


                Toast.makeText(context, "0"+
                        " Database has not been updated!", Toast.LENGTH_SHORT).show();


                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Log.e(TAG, "Connection Error: " + error.getMessage());

        }
    }) {
        protected Map<String, String> getParams() {
            HashMap<String ,String> params=new HashMap<String, String>();
            params.put("tag", "getNewMedia");
            return params;
        }
    };
    // Adding request to request queue
    AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
    System.out.println(strReq + tag_string_req);


}

Listener.php

else if ($tag == 'getNewMedia') {    

    $db_functions->copyNewMediaToSongs($mysqli);
        
     if ($test ) {

        $response["error"] = FALSE;
        echo json_encode($response);
        
        
    } else {
   
        $response["error"] = TRUE;
        $response["error_msg"] = "Server Error";
        echo json_encode(array_values($response));
    }
}

One of the Functions that causes null error

  public function copyNewMediaToSongs($mysqli) {


   shell_exec('sudo sh /var/www/html/musicbox/include/findmp3.sh');
   return 1;

   }

What Logcat shows me ...

08-09 04:16:01.420 2812-2979/com.ruecgames.sengproject.musicbox I/System.out: [ ] http://192.168.2.123/musicbox/include/Listener.php 0x85ca2597 NORMAL 18admin_control 08-09 04:16:09.008 2812-2812/com.ruecgames.sengproject.musicbox E/getConfig: Connection Error: null

Hey thanks for your hint, I updated it. But its not much what logcat shows me — Mori Ruec, Aug 09 '16 at 04:22
dunno if it helps but I get the same error if I enter an IP which is not available — Mori Ruec, Aug 09 '16 at 04:25
why don't you put a printstacktrace there and let it show you more. — muratgu, Aug 09 '16 at 04:27
where exactly do you mean? the only thing I get back is just null — Mori Ruec, Aug 09 '16 at 04:37
I found a fix posted below, which lead me to another problem posted here: http://stackoverflow.com/questions/38877348/query-very-slow-30s-in-php-but-fast-when-running-the-query-in-phpmyadmin — Mori Ruec, Aug 10 '16 at 15:18

score 0 · Accepted Answer · answered Aug 10 '16 at 14:42

Not sure what really solved it (I think its the retry policy I added), but with this code the null error is gone. What found out now, they query im executing takes waay to long, and I dont know why. I post it in another question, link will be in the comments

 public static  void registerUser(final Context context){


    StringRequest stringRequest = new   StringRequest(Request.Method.POST,   AppConfig.URL_SERVER,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    Toast.makeText(context,response,Toast.LENGTH_LONG).show();
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    Toast.makeText(context,error.toString(),Toast.LENGTH_LONG).show();
                }
            }){
        @Override
        protected Map<String,String> getParams(){
            Map<String,String> params = new HashMap<String, String>();
            params.put("tag", "getNewMedia");
            return params;
        }

    };

    stringRequest.setRetryPolicy(new DefaultRetryPolicy(
            100000,
            DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
            DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));

    RequestQueue requestQueue = Volley.newRequestQueue(context);
    requestQueue.add(stringRequest);
}

Getting Android Volley null error after calling specific php functions, other functions work fine

Java/Volley Post

Listener.php

One of the Functions that causes null error

What Logcat shows me ...

1 Answers1