How to retrieve data based on current user logged in on android

Question

Sections.class

private void loadSection() {
  final String username = SharedPrefManager.getInstance(getActivity()).getUsername();
final String userSection_URL = Constants.USER_SECTION + "?username=" + username;
  JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, userSection_URL, null, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            try {
                JSONArray jsonArray = response.getJSONArray("data");
                for (int i = 0; i < jsonArray.length(); i++) {
                    JSONObject sections = (JSONObject) jsonArray.get(i);
                    sectionList.add(new ListGradeData(
                            sections.getInt("id"),
                            sections.getString("section"),
                            sections.getString("year_level"),
                            sections.getString("school_year")
                    ));

                    //creating adapter object and setting it to recyclerview
                    LatestGradeAdapter adapter = new LatestGradeAdapter(getActivity(), sectionList);
                    recyclerView.setAdapter(adapter);
                }
            } catch (JSONException e) {
                e.printStackTrace();
                Toast.makeText(getContext(), "No Data", Toast.LENGTH_LONG).show();
            }
            // Stopping swipe refresh
            mSwipeRefreshLayout.setRefreshing(false);
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            // Stopping swipe refresh
            mSwipeRefreshLayout.setRefreshing(false);

            headerSection.setVisibility(View.GONE);
            noConnectionLayout.setVisibility(View.VISIBLE);
        }
    });
    //adding our stringrequest to queue
    Volley.newRequestQueue(getActivity().getApplicationContext()).add(jsonObjectRequest);
}

userSection.php

require_once "../include/Constants.php";

$conn = new mysqli(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);

if($_SERVER['REQUEST_METHOD']=='GET'){ $uname = trim($_GET['username']);

if(isset($uname)){
    $query = "SELECT * FROM students WHERE s_id = '".$uname."' ";
    $tbl = mysqli_query($conn, $query);
    if(mysqli_num_rows($tbl)>0) {
        $row = mysqli_fetch_array($tbl, MYSQLI_ASSOC);
        $uid = $row['id'];
        $stmt = $conn->prepare("SELECT students.id, sections.name AS section_name, years.name AS year_level, CONCAT(academic_years.start, '-', academic_years.end) AS school_year FROM students INNER JOIN section_student ON students.id = section_student.student_id INNER JOIN sections ON section_student.section_id = sections.id INNER JOIN years ON sections.year_id = years.id INNER JOIN academic_years ON sections.academic_year_id = academic_years.id WHERE students.id = ?");
    $stmt->bind_param("s", $uname);
    $stmt->execute();
    $stmt->bind_result($id, $section, $year_level, $school_year);
    $sections = array(); 

    //traversing through all the result 
    while($stmt->fetch()){
      $temp = array();
      $temp['id'] = $id; 
      $temp['section'] = $section; 
      $temp['year_level'] = $year_level; 
      $temp['school_year'] = $school_year; 
      array_push($sections, $temp);
    }
        echo json_encode(array('data' => $sections));
    }else {
        echo json_encode(array('data' => "No Data"));
    }
}

} PROBLEM SOLVED!

I have a problem, When it comes to retrieving a data. I want to retrieve a information based on the username that current logged in. But it doesn't work. I already try to display all the data, but it is not based on the current user logged in. It will display all the data. the main problem is How I will retrieve a data based on the current user logged in. my current user logged in is based on this code final String username = SharedPrefManager.getInstance(getActivity()).getUsername();

Answer 1

No username in StringRequest

In your PHP code you are looking for a username url parameter at $uname = trim($_GET['username']);. But you are not sending it from Volley StringRequest. Your url is defined by Constants.USER_SECTION. If this is the endpoint for the request you should add the parameter to the url with something like this:

String url = Constants.USER_SECTION + '?username=' + username; //considering that Constants.USER_SECTION doesn't have any url params
StringRequest stringRequest = new StringRequest(Request.Method.GET, url ,
            new Response.Listener<String>() {
               ...

Debug your code

After fixing the errors above, debug your code with these steps:

1. Check final String username value. If it is wrong, verify where you have saved it to SharedPreferences.
2. Check url value before StringRequest. If it is wrong check where Constants.USER_SECTION is defined.
3. Check response from StringRequest. If it is wrong debug your server side code using a REST client of even a browser.

Answer 2

I will suggest using JSONObjectRequest. It will allow you to retrieve objects.

String url = YOUR_OWN_URL + "?username=" + username;
JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
    @Override
    public void onResponse(JSONObject response) {
        try {
            JSONArray jsonArray = response.getJSONArray("data");
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObject = (JSONObject) jsonArray.get(i);
                int id = jsonObject.getInt("id");
                String section = jsonObject.getString("section");
                String year_level = jsonObject.getString("year_level");
                String school_year = jsonObject.getString("school_year");
                // insert your own logic
            }
        } catch (JSONException e) {
        }
    }
}, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
    }
});

And, in the PHP, I will change the json_encode part into like this.

echo json_encode(array('data' => $sections));