btnlogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String username = txt_username.getText().toString();
                String password = txt_password.getText().toString();
                ConnectionDetector conn = new ConnectionDetector();

                // mengecek kolom yang kosong
                if (username.trim().length() > 0 && password.trim().length() > 0) {
                    if (conMgr.getActiveNetworkInfo() != null
                            && conMgr.getActiveNetworkInfo().isAvailable()
                            && conMgr.getActiveNetworkInfo().isConnected()) {
                        if(conn.webTerhubung()){
                            Toast.makeText(getApplicationContext() ,"Gagal terhubung ke server!", Toast.LENGTH_LONG).show();
                        }else {
                            checkLogin(username, password);
                        }

                    } else {
                        Toast.makeText(getApplicationContext() ,"No Internet Connection", Toast.LENGTH_LONG).show();
                    }
                } else  {
                    // Prompt user to enter credentials
                    Toast.makeText(getApplicationContext() ,"Kolom tidak boleh kosong", Toast.LENGTH_LONG).show();
                }
            }

        });