Good solutions explained pretty well here. But Here is one more.
Create your own CustomContextWrapper class extending ContextWrapper and use it to change Locale setting for the complete application.
Here is a GIST with usage.
And then call the CustomContextWrapper with saved locale identifier e.g. 'hi' for Hindi language in activity lifecycle method attachBaseContext. Usage here:
@Override
protected void attachBaseContext(Context newBase) {
// fetch from shared preference also save the same when applying. Default here is en = English
String language = MyPreferenceUtil.getInstance().getString("saved_locale", "en");
super.attachBaseContext(MyContextWrapper.wrap(newBase, language));
}