private void volley() {

        String url = "http://x...content-available-to-author-only...x.xxx/A.php";

      /* 不同Button 對應不同 PHP
        String url = "http://x...content-available-to-author-only...x.xxx/B.php";
        String url = "http://x...content-available-to-author-only...x.xxx/C.php";
      */

        JSONObject object = new JSONObject();
        try {
            object.put("水果", "蘋果");

        } catch (JSONException e) {
            e.printStackTrace();
        }

        JsonObjectRequest mJsonObjectRequest = new JsonObjectRequest
                (Request.Method.POST, url, object, new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {
                        try {
                             retStr.setText( response.toString()) ;

                        } catch (Exception e) {

                        }
                    }
                },
                        new Response.ErrorListener() {
                            @Override
                            public void onErrorResponse(VolleyError error) {
                                if (null != error) {
                                    Log.i("Volley", "錯誤訊息:" + error.toString()
                                    );

                                }
                            }
                        });

        mRequestQueue.add(mJsonObjectRequest);

    }