Sunday, March 31, 2013

Programmatically change language in Android-application

Programmatically change language in Android-application
Sometimes it is necessary in the application provide an opportunity the user to change the language of the application, regardless of the locale device. In this article I will show you how to do it.



Preparing resources

Create the string resources for four languages: English, Russian, French and German.
Source code values/strings.xml (English, Default)
<resources>
    <string name="app_name">ChangeLocaleExample</string>    
    <string name="hello_world">Hello World</string>
    <string name="btn_en">English</string>
    <string name="btn_ru">Russian</string>
    <string name="btn_de">German</string>
    <string name="btn_fr">French</string>
</resources>

Source code values-ru/strings.xml (Russian)
<resources>
    <string name="hello_world">Привет, Мир</string>
    <string name="btn_en">Английский</string>
    <string name="btn_ru">Русский</string>
    <string name="btn_de">Немецкий</string>
    <string name="btn_fr">Французский</string>
</resources>

Source code values-fr/strings.xml (French)
<resources>   
    <string name="hello_world">Bonjour monde</string>
    <string name="btn_en">Anglais</string>
    <string name="btn_ru">Russie</string>
    <string name="btn_de">Allemand</string>
    <string name="btn_fr">Français</string>
</resources>

Source code values-de/strings.xml (German)
<resources>   
    <string name="hello_world">Hallo Welt</string>
    <string name="btn_en">Englisch</string>
    <string name="btn_ru">Russisch</string>
    <string name="btn_de">Deutsch</string>
    <string name="btn_fr">Französisch</string>
</resources>

Layout application will consist of four buttons that change the language of the application and the text box to display the greeting line:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/txt_hello"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:gravity="center"
        android:text="@string/hello_world" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:orientation="horizontal"
        android:gravity="center">

        <Button
            android:id="@+id/btn_en"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/btn_en" />
       
        <Button
            android:id="@+id/btn_ru"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/btn_ru" />
       
        <Button
            android:id="@+id/btn_de"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/btn_de" />
       
        <Button
            android:id="@+id/btn_fr"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="@string/btn_fr" />
    </LinearLayout>

</LinearLayout>

Developing an application

Add attributes to our Activity.
  • UI elements:
private TextView txt_hello;
private Button btn_en, btn_ru, btn_fr, btn_de;
  • Current local application:
private Locale myLocale;
Develop necessary methods to change the language in the application.
  • Changing the language in the application:
public void changeLang(String lang)
{
    if (lang.equalsIgnoreCase(""))
     return;
    myLocale = new Locale(lang);
    saveLocale(lang);
    Locale.setDefault(myLocale);
    android.content.res.Configuration config = new android.content.res.Configuration();
    config.locale = myLocale;
    getBaseContext().getResources().updateConfiguration(config, getBaseContext().getResources().getDisplayMetrics());
    updateTexts();
}

  • Save the current locale:
public void saveLocale(String lang)
{
    String langPref = "Language";
    SharedPreferences prefs = getSharedPreferences("CommonPrefs", Activity.MODE_PRIVATE);
    SharedPreferences.Editor editor = prefs.edit();
    editor.putString(langPref, lang);
    editor.commit();
}

  • Loading a saved locale:
public void loadLocale()
{
    String langPref = "Language";
    SharedPreferences prefs = getSharedPreferences("CommonPrefs", Activity.MODE_PRIVATE);
    String language = prefs.getString(langPref, "");
    changeLang(language);
}

  • Updating the UI elements of the current screen (you need to update only the screen in which a change of locale): 
private void updateTexts()
{
 txt_hello.setText(R.string.hello_world);
 btn_en.setText(R.string.btn_en);
 btn_ru.setText(R.string.btn_ru);
 btn_fr.setText(R.string.btn_fr);
 btn_de.setText(R.string.btn_de);
}

Add events to the buttons. For this implement OnClickListener interface for our Activity (implements OnClickListener). And implement the method onClick().
public void onClick(View v) {
  String lang = "en";
  switch (v.getId()) {
  case R.id.btn_en:
   lang = "en";
   break;
  case R.id.btn_ru:
   lang = "ru";
   break;
  case R.id.btn_de:
   lang = "de";
   break;
  case R.id.btn_fr: 
   lang = "fr";
   break;   
  default:
   break;
  }
  changeLang(lang);
 }

Finally, consistent with the work with the change of language in the method onCreate () of our Activity:
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
  
  this.txt_hello = (TextView)findViewById(R.id.txt_hello);
  this.btn_en = (Button)findViewById(R.id.btn_en);
  this.btn_ru = (Button)findViewById(R.id.btn_ru);
  this.btn_fr = (Button)findViewById(R.id.btn_fr);
  this.btn_de = (Button)findViewById(R.id.btn_de);
  
  this.btn_en.setOnClickListener(this);
  this.btn_ru.setOnClickListener(this);
  this.btn_fr.setOnClickListener(this);
  this.btn_de.setOnClickListener(this);
  
  loadLocale();
 }

Links

  • The source codes of this project can be downloaded here: zip