java - JavaFX: Change application language on the run

Question

I am making JavaFX desktop application with core components described in FXML and I would like to offer user the option to change the language. However I have not find any direct way how to change the language once the component has been loaded from the FXML.

The question is is there any standard way how to deal with switching the language in JavaFX.

Answer 1

You can do something like this. As in your answer, you would either want to implement this as a singleton, or use a DI framework to inject a single instance wherever you need it:

public class ObservableResourceFactory {

    private ObjectProperty<ResourceBundle> resources = new SimpleObjectProperty<>();
    public ObjectProperty<ResourceBundle> resourcesProperty() {
        return resources ;
    }
    public final ResourceBundle getResources() {
        return resourcesProperty().get();
    }
    public final void setResources(ResourceBundle resources) {
        resourcesProperty().set(resources);
    }

    public StringBinding getStringBinding(String key) {
        return new StringBinding() {
            { bind(resourcesProperty()); }
            @Override
            public String computeValue() {
                return getResources().getString(key);
            }
        };
    }
}

Now you can do things like:

ObservableResourceFactory resourceFactory = .... ;

resourceBundle.setResources(...);

Label greetingLabel = new Label();
greetingLabel.textProperty().bind(resourceFactory.getStringBinding("greeting"));

And any time you update the resource with

resourceFactory.setResources(...);

will cause the label to update its text.

Here's an SSCCE (with apologies for the extremely ugly way of forcing a ResourceBundle into a single runnable class...)

import java.util.ListResourceBundle;
import java.util.Locale;
import java.util.ResourceBundle;

import javafx.application.Application;
import javafx.beans.binding.StringBinding;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Label;
import javafx.scene.control.ListCell;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class ResourceBundleBindingExample extends Application {

    private static final String RESOURCE_NAME = Resources.class.getTypeName() ;

    private static final ObservableResourceFactory RESOURCE_FACTORY = new ObservableResourceFactory();

    static {
        RESOURCE_FACTORY.setResources(ResourceBundle.getBundle(RESOURCE_NAME));
    }

    @Override
    public void start(Stage primaryStage) {
        ComboBox<Locale> languageSelect = new ComboBox<>();
        languageSelect.getItems().addAll(Locale.ENGLISH, Locale.FRENCH);
        languageSelect.setValue(Locale.ENGLISH);
        languageSelect.setCellFactory(lv -> new LocaleCell());
        languageSelect.setButtonCell(new LocaleCell());

        languageSelect.valueProperty().addListener((obs, oldValue, newValue) -> {
            if (newValue != null) {
                RESOURCE_FACTORY.setResources(ResourceBundle.getBundle(RESOURCE_NAME, newValue));
            }
        });

        Label label = new Label();
        label.textProperty().bind(RESOURCE_FACTORY.getStringBinding("greeting"));

        BorderPane root = new BorderPane(null, languageSelect, null, label, null);
        root.setPadding(new Insets(10));
        Scene scene = new Scene(root, 400, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static class LocaleCell extends ListCell<Locale> {
        @Override
        public void updateItem(Locale locale, boolean empty) {
            super.updateItem(locale, empty);
            if (empty) {
                setText(null);
            } else {
                setText(locale.getDisplayLanguage(locale));
            }
        }
    }

    public static class ObservableResourceFactory {

        private ObjectProperty<ResourceBundle> resources = new SimpleObjectProperty<>();
        public ObjectProperty<ResourceBundle> resourcesProperty() {
            return resources ;
        }
        public final ResourceBundle getResources() {
            return resourcesProperty().get();
        }
        public final void setResources(ResourceBundle resources) {
            resourcesProperty().set(resources);
        }

        public StringBinding getStringBinding(String key) {
            return new StringBinding() {
                { bind(resourcesProperty()); }
                @Override
                public String computeValue() {
                    return getResources().getString(key);
                }
            };
        }

    }

    public static class Resources extends ListResourceBundle {

        @Override
        protected Object[][] getContents() {
            return new Object[][] {
                    {"greeting", "Hello"}
            };
        }

    }

    public static class Resources_fr extends ListResourceBundle {

        @Override
        protected Object[][] getContents() {
            return new Object[][] {
                    {"greeting", "Bonjour"}
            };
        }

    }

    public static void main(String[] args) {
        launch(args);
    }
}