Login Volley

import android.app.ProgressDialog;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.EditText;

import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.d4mdp.plesir.R;
import com.d4mdp.plesir.app.AppController;
import com.d4mdp.plesir.entity.User;
import com.d4mdp.plesir.util.CustomRequest;
import com.d4mdp.plesir.util.Utilities;

import org.json.JSONArray;
import org.json.JSONObject;

import java.util.HashMap;
import java.util.Map;

public class Login extends AppCompatActivity {

    Button btnLogin, btnRegister;
    EditText etUsername, etPassword;

    Utilities util = new Utilities();
//    String phpFile = "login.php";
//    String URL = util.getUrl(phpFile);

    String URL = "http://apps.mdp.ac.id/simasbar/apisimasbar/loginuser.php";
    User user = new User();

    public static final String KEY_USERNAME = "username";
    public static final String KEY_PASSWORD = "password";

    private static final String TAG = Login.class.getSimpleName();

    ProgressDialog progressDialog;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.activity_login);

        etUsername = (EditText) findViewById(R.id.etUsername);
        etPassword = (EditText)findViewById(R.id.etPassword);

        btnLogin = (Button)findViewById(R.id.btnLogin);
        btnRegister = (Button)findViewById(R.id.btnRegister);

        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                loginUser();
            }
        });

        btnRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(getApplicationContext(), Register.class));
            }
        });
    }

    private void loginUser(){
        final String username = etUsername.getText().toString();
        final String password = etPassword.getText().toString();

        progressDialog = new ProgressDialog(Login.this);
        progressDialog.setMessage("Loading...");
        progressDialog.show();

        Log.d(TAG, "Start request...");

        Map<String, String> params = new HashMap<String, String>();
        params.put(KEY_USERNAME, username);
        params.put(KEY_PASSWORD, password);

        System.out.println(URL);


        CustomRequest jsonObj = new CustomRequest(Request.Method.POST,URL, params,
                new Response.Listener<JSONObject>() {

                    @Override
                    public void onResponse(JSONObject response) {
                        try {
                            Log.d(TAG, response.toString());
                            JSONArray jsonArray = response.getJSONArray("data");
                            JSONObject c = jsonArray.getJSONObject(0);
                            String akses = c.getString("akses");
                            System.out.println("akses: " + akses);
                            user.setUsername(getApplicationContext(), username);
                            startActivity(new Intent(getApplicationContext(), MainActivity.class));
                            finish();
                            progressDialog.dismiss();
                        } catch (Exception e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                            progressDialog.dismiss();
                        }
                    }
                }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                progressDialog.dismiss();
            }
        });

        AppController.getInstance().addToRequestQueue(jsonObj);
    }
}