HttpUrlConnection - Use php to connect in Mysql

I am trying to fetch the data of a user saved in an external database to log in / register. But I run the system and there is no exception, but it does not connect. I tested the php that I'm consuming and it's working correctly. If anyone can help me, I'll be grateful.

Class that executes the connection / inserts:

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

Context context;
AlertDialog alertDialog;
String result="";

BackgroundWorker(Context context){
    this.context = context;
}

@Override
protected void onPreExecute () {
    super.onPreExecute();

}
@Override
protected String doInBackground(String... params) {
    String type = params[0];
    String register_url = "http://127.0.0.1/Tutorial/cadastrar.php";
    String login_url = "http://127.0.0.1/Tutorial/login.php";
    if (type.equals("login")) {
        try {
            String user = params[1];
            String pass = 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("username", "UTF-8") + "=" + URLEncoder.encode(user, "UTF-8") + "&"
                    + URLEncoder.encode("password", "UTF-8") + "=" + URLEncoder.encode(pass, "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 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();
        }
    }

MainActivity:

public class MainActivity extends AppCompatActivity {
EditText edtLogin;
EditText edtPass;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    edtLogin = (EditText) findViewById(R.id.edtLogin);
    edtPass = (EditText) findViewById(R.id.edtPassword);

}

public void onLogin(View view){
    String username = edtLogin.getText().toString();
    String password = edtPass.getText().toString();
    String type = "login";

    BackgroundWorker bkw = new BackgroundWorker(this);
    bkw.execute(type, username, password);

}

public void actCadastrar(View view){
    startActivity(new Intent(MainActivity.this, Cadastrar.class));
}
}

Php Connection and then php login:

<?php
try {
    $conexao = new PDO("mysql:host=127.0.0.1;dbname=escola", 'root', '') ;
    $conexao->exec("set names utf-8") ;
    $conexao->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION) ;
    echo 'Conectado';
} catch (PDOException $e) {
    echo 'ERRO: ' . $e->getMessage() ;
}
?>

<?php
session_start() ;

$user = $_POST["user"] ;
$pass = $_POST["pass"] ;

try {
    require('conexao.php') ;
    $sql = "SELECT * FROM escola_tabela Where username = :username And password = :password" ;
    $stmt = $conexao->prepare($sql) ;
    $stmt->execute(array('username' => $user, 'password' => $pass)) ;

    $logou = 0 ;

    while($consulta = $stmt->fetch()) {
        $user = $consulta["username"] ;
        $pass = $consulta["password"] ;

        $_SESSION['username'] = $user ;
        $_SESSION['password'] = $pass ;

        $logou = 1 ;

        echo 'Logado com sucesso';
    }

    if ($logou == 0) {
        echo 'Usuário/Senha inválido...: ' ;
    }


} catch (PDOException $e) {
    echo 'ERRO: ' . $e->getMessage() ;
}

?>