Android volley 库，方法返回空对象

Question

我想向我的服务器传递一个 id，它让我查询并向我发送一些信息，但看起来服务器没有捕获我发送的值。 这是我的代码：

private void makeJsonObjectRequest() {



    JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET,
            Config.url_info, null, new Response.Listener<JSONObject>() {

        @Override
        public void onResponse(JSONObject response) {
            Log.d("INFO RESPONSE: ", response.toString());

            try {
                int success = response.getInt(TAG_SUCCESS);
                if(success == 1) {
                    // successfully received details
                    JSONArray infoObj = response.getJSONArray(TAG_INFO); // JSON Array

                    // get first course object from JSON Array
                    info = infoObj.getJSONObject(0);
                    showResult();

                }
            }catch (JSONException e){
                e.printStackTrace();
                Toast.makeText(getApplicationContext(),"Error: " + e.getMessage(),
                        Toast.LENGTH_LONG).show();
            }


        }
    }, new Response.ErrorListener() {

        @Override
        public void onErrorResponse(VolleyError error) {
            VolleyLog.d("VOLLEY ERROR: ", "Error: " + error.getMessage());
            Toast.makeText(getApplicationContext(),
                    error.getMessage(), Toast.LENGTH_SHORT).show();


        }
    }){
    @Override
    protected Map<String, String> getParams() throws AuthFailureError {
        Map<String,String> params = new HashMap<>();
        //Adding parameters to request
        params.put("id", id);
        //returning parameter
        return params;
    }
};

    // Adding request to request queue
    //AppController.getInstance().addToRequestQueue(jsonObjReq);
    RequestQueue requestQueue = Volley.newRequestQueue(this);
    requestQueue.add(jsonObjReq);
}

错误在变量信息中，错误日志说是空值。 “java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法'java.lang.String org.json.JSONObject.getString(java.lang.String)'”

这是我的php代码：

<?php

// array for JSON response
$response = array();

// include db connect class
require_once __DIR__ . '/db_connect.php';
//include query class
require_once __DIR__ . '/query.php';

// connecting to db
$db = new DB_CONNECT();

// check for post data

if (isset($_GET["id"])) {
    $id = $_GET['id'];

    // get a product from products table
    $result = $db ->sth -> query("SELECT * FROM info WHERE id = $id");

    if (!empty($result)) {
      // check for empty result
      if (mysqli_num_rows($result) > 0) {

        $result = mysqli_fetch_array($result);
        $dett = array();
        $dett["where"] = $result["where"];
        $dett["when"] = $result["when"];
        $dett["cost"] = $result["cost"];
        $dett["link"] = $result["link"];

        // success
        $response["success"] = 1;

        // user node
        $response["info"] = array();

        array_push($response["info"], $dett);

        // echoing JSON response
        echo json_encode($response);
    } else {
        // no product found
        $response["success"] = 0;
        $response["message"] = "No course found";

        // echo no users JSON
        echo json_encode($response);
    }
} else {
    // no product found
    $response["success"] = 0;
    $response["message"] = "No course found";

    // echo no users JSON
    echo json_encode($response);
}
} else {
// required field is missing
$response["success"] = 0;
$response["message"] = "Required field(s) is missing";

// echoing JSON response
echo json_encode($response);
}
?>

感谢阅读。

编辑。我尝试更改我的 php 文件，如果我使用特定数字设置变量 $id 它可以工作，所以问题可能出在 $_get for php 中（但我不认为因为以前我使用的是旧库并且它有效)，我尝试在 map 方法中插入一条 toast 消息，但没有显示出来。 屏幕保持白色，成功值为0

Answer 1

试着做这样的代码..

public void sendContactMessage(final String sfullname, final String semail, final String smessage){
    class DownloadJSONsendContactMessage extends AsyncTask<String, Void, String> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            mProgressDialog = ProgressDialog.show(getActivity(), null, null, true, false);
            mProgressDialog.setContentView(R.layout.progressdialog);
        }

        @Override
        protected String doInBackground(String... params) {
            ArrayList<NameValuePair> dataToSend = new ArrayList<>();
            dataToSend.add(new BasicNameValuePair("fullname", sfullname));
            dataToSend.add(new BasicNameValuePair("email", semail));
            dataToSend.add(new BasicNameValuePair("message", smessage));

            HttpParams httpRequestParams = new BasicHttpParams();
            HttpConnectionParams.setConnectionTimeout(httpRequestParams, CONNECTION_TIMEOUT);
            HttpConnectionParams.setSoTimeout(httpRequestParams, CONNECTION_TIMEOUT);

            DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams());
            HttpPost httppost = new HttpPost(SERVER_ADDRESS + "sendcontactmessage.php");

            // Depends on your web service
            //httppost.setHeader("Content-type", "application/json");

            InputStream inputStream = null;
            String sendcontactresult = null;
            try {
                httppost.setEntity(new UrlEncodedFormEntity(dataToSend));
                HttpResponse response = httpclient.execute(httppost);
                HttpEntity entity = response.getEntity();

                inputStream = entity.getContent();
                // json is UTF-8 by default
                BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
                StringBuilder sb = new StringBuilder();

                String line = null;
                while ((line = reader.readLine()) != null)
                {
                    sb.append(line + "\n");
                }
                sendcontactresult = sb.toString();
            } catch (Exception e) {
                // Oops
            }
            finally {
                try{if(inputStream != null)inputStream.close();}catch(Exception squish){}
            }
            return sendcontactresult;
        }

        @Override
        protected void onPostExecute(String sendcontactresult){
            // Close the progressdialog
            mProgressDialog.dismiss();
            sendcontactsuccessful();
        }
    }
    DownloadJSONsendContactMessage g = new DownloadJSONsendContactMessage();
    g.execute();
}