Crea App multilenguaje con Android Studio

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="net.jc_mouse.appmultilenguaje.MainActivity">

    <TextView
        android:id="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Button"/>

</LinearLayout>

<resources>
    <string name="app_name">App Multilenguaje</string>
</resources>

<resources>
    <string name="app_name">App Multilenguaje</string>
    <string name="str_textview">Hello World!!!</string>
    <string name="str_button">Change Language</string>
</resources>

    <TextView
        android:id="@+id/textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/str_textview" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/str_button"/>

    <string name="str_en" >English</string>
    <string name="str_es" >Spanish</string>
    <string name="str_pt" >Portuguese</string>
    <string-array name="languages" >
        <item>@string/str_en</item>
        <item>@string/str_es</item>
        <item>@string/str_pt</item>
    </string-array>

package net.jc_mouse.appmultilenguaje;

import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.res.Configuration;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import java.util.Locale;

public class MainActivity extends AppCompatActivity {

    private Button button;
    private TextView textview;
    private Locale locale;
    private Configuration config = new Configuration();

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

        button = ((Button)findViewById(R.id.button));
        textview = ((TextView)findViewById(R.id.textview));

        button.setOnClickListener(
                new View.OnClickListener() {
                    public void onClick(View view) {
                        showDialog();
                    }});
    }

    /**
     * Muestra una ventana de dialogo para elegir el nuevo idioma de la aplicacion
     * Cuando se hace clic en uno de los idiomas, se cambia el idioma de la aplicacion
     * y se recarga la actividad para ver los cambios
     * */
    private void showDialog(){
        AlertDialog.Builder b = new AlertDialog.Builder(this);
        b.setTitle(getResources().getString(R.string.str_button));
        //obtiene los idiomas del array de string.xml
        String[] types = getResources().getStringArray(R.array.languages);
        b.setItems(types, new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int which) {

                dialog.dismiss();
                switch(which){
                    case 0:
                        locale = new Locale("en");
                        config.locale =locale;
                        break;
                    case 1:
                        locale = new Locale("es");
                        config.locale =locale;
                        break;
                    case 2:
                        locale = new Locale("pt");
                        config.locale =locale;
                        break;
                }
                getResources().updateConfiguration(config, null);
                Intent refresh = new Intent(MainActivity.this, MainActivity.class);
                startActivity(refresh);
                finish();
            }

        });

        b.show();
    }

}