How to change Android O / Oreo / api 26 app language

I had the same problem: since Android 8.0+ some parts of my app did't change their language anymore. Updating of both application and activity context helps me. Here is an example of MainActivity function:

private void setApplicationLanguage(String newLanguage) {
    Resources activityRes = getResources();
    Configuration activityConf = activityRes.getConfiguration();
    Locale newLocale = new Locale(newLanguage);
    activityConf.setLocale(newLocale);
    activityRes.updateConfiguration(activityConf, activityRes.getDisplayMetrics());

    Resources applicationRes = getApplicationContext().getResources();
    Configuration applicationConf = applicationRes.getConfiguration();
    applicationConf.setLocale(newLocale);
    applicationRes.updateConfiguration(applicationConf, 
    applicationRes.getDisplayMetrics());
}

Yes in android Oreo localization is not working fine with updateconfiguration. But it is deprecated in android N itself. Instead of updateconfiguration use createconfiguration in each attachcontext. it is working fine for me. Try this...

In you activity add this..

@Override
protected void attachBaseContext(Context newBase) {
    if(Build.VERSION.SDK_INT > Build.VERSION_CODES.N_MR1) {
        super.attachBaseContext(MyContextWrapper.wrap(newBase, "ta"));
    }
    else {
        super.attachBaseContext(newBase);
    }
}

In MyContextWrapper.java

 public static ContextWrapper wrap(Context context, String language) {
    Resources res = context.getResources();
    Configuration configuration = res.getConfiguration();
    Locale newLocale = new Locale(language);

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        configuration.setLocale(newLocale);
        LocaleList localeList = new LocaleList(newLocale);
        LocaleList.setDefault(localeList);
        configuration.setLocales(localeList);
        context = context.createConfigurationContext(configuration);

    } else if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
        configuration.setLocale(newLocale);
        context = context.createConfigurationContext(configuration);

    } else {
        configuration.locale = newLocale;
        res.updateConfiguration(configuration, res.getDisplayMetrics());
    }

    return new ContextWrapper(context);
}

updateConfiguration is deprecated and you should use createConfigurationContext. I solved it this way:

    @Override
    protected void attachBaseContext(Context newBase) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            Configuration config = newBase.getResources().getConfiguration();
            //Update your config with the Locale i. e. saved in SharedPreferences
            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(newBase);
            String language = prefs.getString(SP_KEY_LANGUAGE, "en_US");
            Locale.setDefault(locale);
            config.setLocale(new Locale(language));
            newBase = newBase.createConfigurationContext(config);
        }
        super.attachBaseContext(newBase);
    }

Updated For All android versions till Oreo

Create a class like this

public class LocaleUtils {

@Retention(RetentionPolicy.SOURCE)
@StringDef({ENGLISH, FRENCH, SPANISH})
public @interface LocaleDef {
    String[] SUPPORTED_LOCALES = {ENGLISH, FRENCH, SPANISH};
}

public static final String ENGLISH = "en";
public static final String FRENCH = "fr";
public static final String SPANISH = "es";


public static void initialize(Context context) {
    setLocale(context, ENGLISH);
}

public static void initialize(Context context, @LocaleDef String defaultLanguage) {
    setLocale(context, defaultLanguage);
}


public static boolean setLocale(Context context, @LocaleDef String language) {
    return updateResources(context, language);
}

private static boolean updateResources(Context context, String language) {
    Locale locale = new Locale(language);
    Locale.setDefault(locale);
    Resources resources = context.getResources();
    Configuration configuration = resources.getConfiguration();
    context.createConfigurationContext(configuration);
    configuration.locale = locale;
    resources.updateConfiguration(configuration, resources.getDisplayMetrics());
    return true;
}

}

Now when you select the language from your app, Save the language code in Shared Preference like below

private static SharedPreferences getDefaultSharedPreference(Context context) {
    if (PreferenceManager.getDefaultSharedPreferences(Application.getInstance().getApplicationContext()) != null)
        return PreferenceManager.getDefaultSharedPreferences(Application.getInstance().getApplicationContext());
    else
        return null;
}

 public static void setSelectedLanguageId(String id){
    final SharedPreferences prefs = getDefaultSharedPreference(Application.getInstance().getApplicationContext());
    SharedPreferences.Editor editor = prefs.edit();
    editor.putString("app_language_id", id);
    editor.apply();
}

public static String getSelectedLanguageId(){
    return getDefaultSharedPreference(Application.getInstance().getApplicationContext())
            .getString("app_language_id", "en");
}

These three functions should be written inside a Utiltiy class(your preference). Then when you select the app language from the app, call the setSelectedLanguageId() function and pass the language id as parameter.

This way you have saved the selected language in your app. Now in your application class write a function like this

public void initAppLanguage(Context context){
    LocaleUtils.initialize(context, PreferenceUtil.getSelectedLanguageId() );
}

Here the PreferenceUtil is my Utiltiy class. You should replace it with your utility class function.

You should also create a variable in your application class

private static Application applicationInstance;

and in your Application class's onCreate method, initialise applicationInstance to be the applications context like this

applicationInstance = this; 

Now write a getter function in your application class

public static synchronized Application getInstance() {
    return applicationInstance;
}

And now when you start your first activity, call this method in your activity's onCreate

Application.getInstance().initAppLanguage(this);

Remember that we are passing the activity's context to the initAppLanguage() function, not the application context. Passing the Application context won't make it work in Oreo(atleast for me).

So when you select the language try to restart your application completely. You can acheive this by

Intent i = getBaseContext().getPackageManager().getLaunchIntentForPackage(getBaseContext().getPackageName());

startActivity(i);

Hope this helps you!

It is possible, however i would not recommend to set the language programatically

Android is designed so the System UI and your App have the same language, if you change it programmatically you would be fighting the system

Instead what you can do is enable multilanguage support by adding different strings.xml languages, this will change the language automatically

I reccommend reading through this Google Developers article:

Supporting Different Languages and Cultures

If you really need to change it programatically you can do the following

Locale locale = new Locale("en");
Locale.setDefault(locale);

Configuration config = context.getResources().getConfiguration();
config.setLocale(locale);
context.createConfigurationContext(config);
context.getResources().updateConfiguration(config, context.getResources().getDisplayMetrics());

On SDK >= 21, you need to call 'Resources.updateConfiguration()', otherwise resources will not be updated.

Hope it helps.