public class MainActivity extends ActionBarActivity {

    EditText UsernameEt, PasswordEt;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        UsernameEt = (EditText)findViewById(R.id.etUserName);
        PasswordEt = (EditText)findViewById(R.id.etPassword);

    }


    public void OnLogin(View view) {
        String username = UsernameEt.getText().toString();
        String password = PasswordEt.getText().toString();
        String type = "login";
        BackgroundWorker backgroundWorker = new BackgroundWorker(this);
        backgroundWorker.execute(type, username, password);



    }

}

public class BackgroundWorker extends AsyncTask<String,Void,String> {

    Context context;

    AlertDialog alertDialog;

    BackgroundWorker (Context ctx) {
        context = ctx;

    }

    @Override
    protected String doInBackground(String... params) {
        String type = params[0];

        String login_url = "http://10.127.127.1/ws/login.php";

        if(type.equals("login")) {
            try {

                String user_name = params[1];
                String password = params[2];
                URL url = new URL(login_url);
                HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
                httpURLConnection.setRequestMethod("POST");
                httpURLConnection.setDoOutput(true);
                httpURLConnection.setDoInput(true);
                OutputStream outputStream = httpURLConnection.getOutputStream();
                BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
                String post_data = URLEncoder.encode("user_name","UTF-8")+"="+URLEncoder.encode(user_name,"UTF-8")+"&"
                        +URLEncoder.encode("password","UTF-8")+"="+URLEncoder.encode(password,"UTF-8");
                bufferedWriter.write(post_data);
                bufferedWriter.flush();
                bufferedWriter.close();
                outputStream.close();
                InputStream inputStream = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));
                String result="";
                String line="";

                while((line = bufferedReader.readLine())!= null) {
                    result += line;
                }

                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();
                return result;


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

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

            }
        }


        return null;
    }


    @Override
    protected void onPreExecute() {
        alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setTitle("Status do login");

    }

    @Override
    protected void onPostExecute(String result) {
        alertDialog.setMessage(result);
        alertDialog.show();

    }

    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }


}

<?php
require "conn.php";
$user_name = $_POST["user_name"];
$user_pass = $_POST["password"];
$mysql_qry = "select * from login where username like '$user_name' and password like '$user_pass';";
$result = mysqli_query($conn ,$mysql_qry);
if(mysqli_num_rows($result) > 0) {
echo "login success !!!!! Welcome user";
}
else {
echo "login not success";
}

?>