Javafx: Reusable collections using FXML

Question

I'd like to bind a single collection to multiple ChoiceBox's in FXML. However the only way I know how is using:

<ChoiceBox fx:id="cb00" prefWidth="150.0" GridPane.rowIndex="0" GridPane.columnIndex="0">
    <items>
        <FXCollections fx:id="test" fx:factory="observableArrayList">
            <String fx:value="1" />
            <String fx:value="2" />
            <String fx:value="3" />
            <String fx:value="4" />
            <String fx:value="5" />
            <String fx:value="6" />
            <String fx:value="7" />
            <String fx:value="8" />
            <String fx:value="9" />
        </FXCollections>
    </items>
</ChoiceBox>

Is it possible to declare the collection in the controller and refer to it in FXML instead of copying the collection for each ChoiceBox?

Answer 1

You can define the items in the controller:

public class Controller {

    private ListProperty<String> choiceBoxItems = new SimpleListProperty(FXCollections.observableArrayList());

    public Controller() {
        IntStream.range(1,10).mapToObj(i -> Integer.toString(i))
            .forEach(choiceBoxItems::add);
    }

    public ListProperty<String> choiceBoxItemsProperty() {
        return choiceBoxItems ;
    }

    public ObservableList<String> getChoiceBoxItems() {
        return choiceBoxItemsProperty().get() ;
    }

    public void setComboBoxItems(ObservableList<String> choiceBoxItems) {
        choiceBoxItemsProperty().set(choiceBoxItems) ;
    }

    // ...
}

and then (this is not tested, but I think it will work):

<ChoiceBox fx:id="cb00" items="${controller.choiceBoxItems}" prefWidth="150.0" GridPane.rowIndex="0" GridPane.columnIndex="0">

See expression binding in the FXML documentation. (It's not actually documented that the controller is available in the FXML namespace with key controller , but I think it is safe to use this.)

You can also just define the list in the FXML using fx:define :

<fx:define>

    <FXCollections fx:id="choiceBoxItems" fx:factory="observableArrayList">
        <String fx:value="1"/>
        <String fx:value="2"/>
        <String fx:value="3"/>
        <!-- ... -->
    </FXCollections>

</fx:define>

and then refer to it in each choice box:

<ChoiceBox fx:id="cb00" items="${choiceBoxItems}" prefWidth="150.0" GridPane.rowIndex="0" GridPane.columnIndex="0">

Answer 2

It can be in the controller or any other class like (the example is for a combobox. The same can be applied to a choicebox):

combo.fxml

<?import javafx.scene.control.ComboBox?>
<ComboBox  fx:id="combo1" items="${itemLoader.items}"  prefWidth="150.0"  
xmlns:fx="http://javafx.com/fxml/1" >
</ComboBox>

Loader class

public class ComboLoader {

    private ObservableList<String> obsStrings;

    public ComboLoader() {

        obsStrings = FXCollections.observableArrayList(createStrings());
    }

    private List<String> createStrings() {
            return IntStream.rangeClosed(0, 5)
                    .mapToObj(i -> "String "+i)
                    .map(String::new)
                    .collect(Collectors.toList());
    }
    //name of this method corresponds to itemLoader.items in xml.
    //if xml name was itemLoader.a this method should have been
    //getA(). A bit odd
    public ObservableList<String> getItems(){

        return obsStrings;
    }
}

test it with:

public class ComboTest extends Application {

    @Override
    public void start(Stage primaryStage) throws IOException {

        primaryStage.setTitle("Populate combo from custom builder");

        Group group = new Group();
        GridPane grid = new GridPane();
        grid.setPadding(new Insets(25, 25, 25, 25));
        group.getChildren().add(grid);

        FXMLLoader loader = new FXMLLoader(getClass().getResource("combo.fxml"));
        loader.getNamespace().put("itemLoader", new ComboLoader());
        ComboBox<String>combo = loader.load();
        grid.add(combo, 0, 0);

        Scene scene = new Scene(group, 450, 175);

        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

Answer 3

You can use <fx:reference> to reference existing objects by their fx:id . Using this tag you can reuse the ObservableList :

<HBox xmlns:fx="http://javafx.com/fxml/1" spacing="10">
    <children>
        <ChoiceBox prefWidth="150.0">
            <items>
                <FXCollections fx:id="test" fx:factory="observableArrayList">
                    <String fx:value="1" />
                    <String fx:value="2" />
                    <String fx:value="3" />
                    <String fx:value="4" />
                    <String fx:value="5" />
                    <String fx:value="6" />
                    <String fx:value="7" />
                    <String fx:value="8" />
                    <String fx:value="9" />
                </FXCollections>
            </items>
        </ChoiceBox>
        <ChoiceBox prefWidth="150.0">
            <items>
                <fx:reference source="test" /> <!-- reuse other list here -->
            </items>
        </ChoiceBox>
    </children>
</HBox>