public class MainActivity extends
  AppCompatActivity {

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

    final EditText id = (EditText) findViewById(R.id.loginid);
    final EditText pass = (EditText) findViewById(R.id.loginpass);

    Button b1 = (Button) findViewById(R.id.buttonlogin);
    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            String username = id.getText().toString();
            String password = pass.getText().toString();
            if (isNetworkAvailable()) {
                RequestBody formBody = new FormBody.Builder()
                        .add("username", username)
                        .add("password", password)
                        .build();


                    try {
                        post(ConstantValues.BASE_URL, formBody, new Callback() {
                            @Override
                            public void onFailure(Call call, IOException e) {
                                Log.e("JSONDemo", "IOException", e);
                            }

                            @Override
                            public void onResponse(Call call, Response response) throws IOException {
                                String res = response.body().string();

                                Log.e("res", " " + res);
                                try {

                                    JSONArray jsonarr = new JSONArray(res);

                                    for (int i = 0; i < jsonarr.length(); i++) {


                                        JSONObject jsonobj = jsonarr.getJSONObject(i);
                                        final String namee = jsonobj.getString("FIRST_NAME");




                                        Log.e("name", " " + namee);

                                    }
                                    runOnUiThread(new Runnable() {
                                        @Override
                                        public void run() {
                                            // you can access all the UI componenet


                                        }
                                    });


                                } catch (Exception e) {
                                    Log.e("JSONDemo", "onResponse", e);


                                }
                            }
                        });
                    } catch (Exception e) {
                        Log.e("JSONDemo", "Post Exception", e);
                    }


            }
        }
    });
}


private boolean isNetworkAvailable() {
    ConnectivityManager connectivityManager
            = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
    return activeNetworkInfo != null && activeNetworkInfo.isConnected();
}


private final OkHttpClient client = new OkHttpClient();

Call post(String url, RequestBody formBody, Callback callback) throws IOException {

    Request request = new Request.Builder()
            .url(url)
            .post(formBody)
            .build();

    Call call = client.newCall(request);
    call.enqueue(callback);
    return call;
}

public void showAlertDialog(String title, String message) {
    final AlertDialog.Builder builder1 = new AlertDialog.Builder(MainActivity.this);
    builder1.setTitle(title);
    builder1.setMessage(message);
    builder1.setCancelable(true);
    builder1.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
            dialogInterface.cancel();
        }
    });
    runOnUiThread(new Runnable() {
        @Override
        public void run() {
            builder1.show();

        }

    });
}
}