title: Can't add Volley parameter
body: <p>I can't get it done...</p>
  
  <p>I need to download json with Volley library, and I need to put inside header and body in POST parameter: </p>
  
  <pre><code>usr = "example@ciao.com";
  pwd = "123Prova!";
  
  String url = "http://localhost:8080/...";
  
  RequestQueue queue = Volley.newRequestQueue(getApplicationContext());
  
  JsonObjectRequest jsonRequest = new JsonObjectRequest(Request.Method.POST, url, null, new Response.Listener&lt;JSONObject&gt;() {
      @Override
      public void onResponse(JSONObject response) {
  
          Log.i("VOLLEY", response.toString());
      }
  }, new Response.ErrorListener() {
      @Override
      public void onErrorResponse(VolleyError error) {
  
          Log.e("VOLLEY", error.toString());
          Toast.makeText(MainActivity.this, "qualche errore", Toast.LENGTH_LONG).show();
      }
  }){
      @Override
      public Map&lt;String, String&gt; getHeaders() {
          Map&lt;String, String&gt; params = new HashMap&lt;&gt;(); 
          params.put("Content-Type", "application/json; charset=utf-8");
          params.put("wellu-client-id", "a056fe5c-1dac-4c12-8b57-8189e45c0b58");
  
          return params;
      }
      @Override
      public Map&lt;String, String&gt; getParams() {
          Map&lt;String, String&gt; params = new HashMap&lt;&gt;(); 
          params.put("email", usr);
          params.put("password", pwd);
  
          return params;
      }
  };
  Volley.newRequestQueue(getApplicationContext()).add(jsonRequest);
  </code></pre>
  
  <p>this parameter work in Postman chrome app... but here brings me in <code>.ErrorListener()</code> and I really don't know why.</p>