Android Volley Display JSON Data

Question

Okay I have this simple app to display data from json..unfortunatelly everytime I run the app, it closed immediately.

I have a working fine api in my server

<?php 
if($_SERVER['REQUEST_METHOD']=='GET'){

mysql_connect("localhost","k4371034_android","android123");
mysql_select_db("k4371034_android");

switch($_GET['case']){
case 'sekolah':
$sql = "SELECT * FROM lokasi_checkin";

$r = mysql_query($sql);

$return_arr = array();
while($row = mysql_fetch_array($r)){
    $row_array['id'] = $row['id'];
    $row_array['image'] = $row['image'];
    $row_array['nama'] = $row['nama'];
    $row_array['long'] = $row['long'];
    $row_array['lat'] = $row['lat'];

    array_push($return_arr,$row_array);
}

echo json_encode($return_arr);
die();
break;

case 'user':
$sql = "SELECT * FROM user";

$r = mysql_query($sql);

$return_arr = array();
while($row = mysql_fetch_array($r)){
    $row_array['id'] = $row['id'];
    $row_array['user'] = $row['user'];
    $row_array['image'] = $row['image'];

    array_push($return_arr,$row_array);
}
echo json_encode($return_arr);
die();
break;
  } 
}

It output just fine.

In java itself.

public class MainActivity extends AppCompatActivity {

// Log tag
private static final String TAG = MainActivity.class.getSimpleName();

// Movies json url
private static final String url = "http://www.lineitopkal.com/android/api.php?case=user";
private ProgressDialog pDialog;
private List<School> schoolList = new ArrayList<School>();
private ListView listView;
private CustomListAdapter adapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    listView = (ListView) findViewById(R.id.list);
    adapter = new CustomListAdapter(this, schoolList);
    listView.setAdapter(adapter);


    pDialog = new ProgressDialog(this);
    // Showing progress dialog before making http request
    pDialog.setMessage("Loading...");
    pDialog.show();

//Creating volley request obj
    JsonArrayRequest schoolReq = new JsonArrayRequest(url,
            new Response.Listener<JSONArray>() {
                @Override
                public void onResponse(JSONArray response) {
                    Log.d(TAG, response.toString());
                    hidePDialog();

                    // Parsing json
                    for (int i = 0; i < response.length(); i++) {
                        try {

                            JSONObject obj = response.getJSONObject(i);
                            School school = new School();
                            school.setThumbnailUrl(obj.getString("image"));
                            school.setName(obj.getString("user"));

                            // adding school to school array
                            schoolList.add(school);

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

                    }

                    // notifying list adapter about data changes
                    // so that it renders the list view with updated data
                    adapter.notifyDataSetChanged();
                }
            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            VolleyLog.d(TAG, "Error: " + error.getMessage());
            hidePDialog();

        }
    });

    // Adding request to request queue
    AppController.getInstance().addToRequestQueue(schoolReq);
}

@Override
public void onDestroy() {
    super.onDestroy();
    hidePDialog();
}

private void hidePDialog() {
    if (pDialog != null) {
        pDialog.dismiss();
        pDialog = null;
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    return true;
  }
}

Cannot see what cause the problem cuz my android studio didn't tell what exactly the problem is....it showed nothing in Logcat.

Any answer will be really appreciated. Thank u

EDIT

Okay it turns out that the problem comes from my AppController class...which giving null pointer exception.

The syntax

public class AppController extends Application {

public static final String TAG = AppController.class.getSimpleName();

private RequestQueue mRequestQueue;
private ImageLoader mImageLoader;

private static AppController mInstance;

@Override
public void onCreate() {
    super.onCreate();
    mInstance = this;
}
public static synchronized AppController getInstance() {
    return mInstance;
}

public RequestQueue getRequestQueue() {
    if (mRequestQueue == null) {
        mRequestQueue = Volley.newRequestQueue(getApplicationContext());
    }

    return mRequestQueue;
}

public ImageLoader getImageLoader() {
    getRequestQueue();
    if (mImageLoader == null) {
        mImageLoader = new ImageLoader(this.mRequestQueue,
                new LruBitmapCache());
    }
    return this.mImageLoader;
}

public <T> void addToRequestQueue(Request<T> req, String tag) {
    // set the default tag if tag is empty
    req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
    getRequestQueue().add(req);
}

public <T> void addToRequestQueue(Request<T> req) {
    req.setTag(TAG);
    getRequestQueue().add(req);
}

public void cancelPendingRequests(Object tag) {
    if (mRequestQueue != null) {
        mRequestQueue.cancelAll(tag);
    }
  }
}

Answer 1

The problem was caused because I didn't properly declared the name of application in Android Manifest.

I supposed to add AppController as the name of the application like below

<application
    android:name=".app.AppController"
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Answer 2

1. Use php code like bellow..

    $sql = "SELECT * FROM user";
   
   $result = $con->query($sql);
    //$con database Connection
   $response_arr = array();
    if ($result->num_rows > 0) {
   
   
    $userDetails = array();
     while ($row = $result->fetch_assoc()) {
        //  $response["id"] = $row["id"];
         $userData[] = array(
         "id" => $row["id"],
          "user" => $row["user"],         
   
        );
   
       }
   
     } else {
     echo "0 results";
   }
   
   $result1['userNodes'] = $userData;
   $json = json_encode($result1);
   echo $json;
   

2. Volley code use like

    private void doLoginAction() {
   
    pDialog.show();
     String url_login = "http://www.lineitopkal.com/android/api.php?case=user";
   
   
   StringRequest stringRequest = new StringRequest(Request.Method.POST, url_login,
           new Response.Listener<String>() {
               @Override
               public void onResponse(String response) {
                   //pDialog.dismiss();
   
   
                   try {
                       JSONObject jsonObject = new JSONObject(response);
                       JSONArray loginNodes = jsonObject.getJSONArray("userNodes");
                       for (int i = 0; i < loginNodes.length(); i++) {
                           JSONObject jo = loginNodes.getJSONObject(i);
                           String id = jo.getString("id");
                           Log.e("id ::",id);                                
                           String user = jo.getString("user");
                           Log.e("user ::",user);
   
   
                       }
                   } catch (JSONException e) {
                       e.printStackTrace();
                   }
   
   
               }
           },
           new Response.ErrorListener() {
               @Override
               public void onErrorResponse(VolleyError error) {
                   pDialog.dismiss();
                   try {
   
                       if (error instanceof TimeoutError ) {
                           //Time out error
   
                       }else if(error instanceof NoConnectionError){
                           //net work error
   
                       } else if (error instanceof AuthFailureError) {
                           //error
   
                       } else if (error instanceof ServerError) {
                           //Erroor
                       } else if (error instanceof NetworkError) {
                           //Error
   
                       } else if (error instanceof ParseError) {
                           //Error
   
                       }else{
                           //Error
                       }
                       //End
   
   
                   } catch (Exception e) {
   
   
                   }
   
               }
           }) {
       @Override
       protected Map<String, String> getParams() {
           Map<String, String> params = new HashMap<>();
           //Post parameter like bellow
           params.put("uname", "era@gmail.com");
           params.put("pass", "123456");
   
   
   
           return params;
       }
   
   };
   
     RequestQueue requestQueue = Volley.newRequestQueue(this);
     requestQueue.add(stringRequest);
    }