How to use Internationalization in tornadofx - kotlin

Question

I am trying to use internationalization in a Kotlin application using the tornadofx framework.
I have created a properties file and depending on the selected language the correct file is loaded. But when I want to change the language in the running application the UI does not update accordingly.

Answer 1

For internationalization you should use a companion object to get the related translation anywhere in your application.
First of all your translation class should know which is the actual selected language/locale. For this I use an enum with the possible locales for the application:
fun setLocale(locale: SupportedLocale) {
if (SupportedLocale.supportedLocals.contains(locale)) {
Locale.setDefault(locale.local)
actualLocal = locale.local
//Good practice would be to store it in a properties file to have the information after restart
} else {
//Throw a warning or sth with your preferred logger
}
}
Then we need a method which gets the particular string value from your resource bundle like:
operator fun get(#PropertyKey(resourceBundle = BUNDLE_NAME) key: String, vararg args: Any): String {
val bundle = ResourceBundle.getBundle(BUNDLE_NAME, actualLocal)
return MessageFormat.format(bundle.getString(key), *args)
}
In JavaFx applications (also TornadoFX) you should use StringBindings (https://docs.oracle.com/javase/8/javafx/api/javafx/beans/binding/StringBinding.html) for example to bind a label text property to your translated string. For that we will implement a special method:
fun createStringBinding(#PropertyKey(resourceBundle = BUNDLE_NAME) key: String, vararg args: Any): StringBinding {
return Bindings.createStringBinding(Callable { get(key, *args) }, Settings.languageProperty())
}
Now you can use your object like this:
textProperty().bind(MyLang.createStringBinding("MyApp.MyTranslation"))
Here an runnable example:
MyLang.kt
enum class SupportedLocale(val local:Locale) {
ENGLISH(Locale.ENGLISH),
GERMAN(Locale.GERMAN);
companion object {
val supportedLocals: List<SupportedLocale>
get() = SupportedLocale.values().toList()
}
}
class MyLang {
companion object {
private const val BUNDLE_NAME = "Language" //prefix of your resource bundle
private var actualLocal = Locale.getDefault()
fun setLocale(locale: SupportedLocale) {
if (SupportedLocale.supportedLocals.contains(locale)) {
Locale.setDefault(locale.local)
actualLocal = locale.local
//Good practice would be to store it in a properties file to have the information after restart
} else {
//Throw a warning or sth with your preferred logger
}
}
operator fun get(#PropertyKey(resourceBundle = BUNDLE_NAME) key: String, vararg args: Any): String {
val bundle = ResourceBundle.getBundle(BUNDLE_NAME, actualLocal)
return MessageFormat.format(bundle.getString(key), *args)
}
fun createStringBinding(#PropertyKey(resourceBundle = BUNDLE_NAME) key: String, vararg args: Any): StringBinding {
return Bindings.createStringBinding(Callable { get(key, *args) }, Settings.languageProperty())
}
}
}
fun main() {
println("My translation: " + MyLang.createStringBinding("MyApp.MyTranslation").get())
//The get() here is only to get the string for assign a property its not needed like in the example
}
If you need any explanations or its unclear. Just ask! Its just written down maybe I forgot something to explain.