val appLocale: LocaleListCompat = LocaleListCompat.forLanguageTags("xx-YY")

// Call this on the main thread as it may require Activity.restart()
AppCompatDelegate.setApplicationLocales(appLocale)


// Call this to get the selected locale and display it in your App
val selectedLocale = AppCompatDelegate.getApplicationLocales()[0]

// Specify the constants to be used in the below code snippets
companion object {

    // Constants for SharedPreference File
    const val PREFERENCE_NAME = "shared_preference"
    const val PREFERENCE_MODE = Context.MODE_PRIVATE

    // Constants for SharedPreference Keys
    const val FIRST_TIME_MIGRATION = "first_time_migration"
    const val SELECTED_LANGUAGE = "selected_language"

    // Constants for SharedPreference Values
    const val STATUS_DONE = "status_done"
}

// Utility method to put a string in a SharedPreference
private fun putString(key: String, value: String) {
    val editor = getSharedPreferences(PREFERENCE_NAME, PREFERENCE_MODE).edit()
    editor.putString(key, value)
    editor.apply()
}

// Utility method to get a string from a SharedPreference
private fun getString(key: String): String? {
    val preference = getSharedPreferences(PREFERENCE_NAME, PREFERENCE_MODE)
    return preference.getString(key, null)
}

// Check if the migration has already been done or not
if (getString(FIRST_TIME_MIGRATION) != STATUS_DONE) {
    
    // Fetch the selected language from wherever it was stored. In this case it’s SharedPref
    // In this case let’s assume that it was stored in a key named SELECTED_LANGUAGE
    getString(SELECTED_LANGUAGE)?.let { it →
        
        // Set this locale using the AndroidX library that will handle the storage itself
        val localeList = LocaleListCompat.forLanguageTags(it)
        AppCompatDelegate.setApplicationLocales(localeList)
            
        // Set the migration flag to ensure that this is executed only once
        putString(FIRST_TIME_MIGRATION, STATUS_DONE)
    }
}