Is it possible to create dynamic Bindings.OR in JavaFX?

Question

Lets consider the following situation. There is a Pane parentPane and there are Pane firstChildPane, secondChildPane, thirdChildPane .... Child panes a

Answer 1

You can try something along the following lines:

// list that fires updates if any members change visibility:
ObservableList<Node> children = 
    FXCollections.observableArrayList(n -> new Observable[] {n.visibleProperty()});
// make the new list always contain the same elements as the pane's child list:
Bindings.bindContent(children, parentPane.getChildren());
// filter for visible nodes:
ObservableList<Node> visibleChildren = children.filter(Node::isVisible);
// and now see if it's empty:
BooleanBinding someVisibleChildren = Bindings.isNotEmpty(visibleChildren);
// finally:
parentPane.visibleProperty().bind(someVisibleChildren);

Another approach is to create your own BooleanBinding directly:

Pane parentPane = ... ;

BooleanBinding someVisibleChildren = new BooleanBinding() {


    {
        parentPane.getChildren().forEach(n -> bind(n.visibleProperty()));

        parentPane.getChildren().addListener((Change<? extends Node> c) -> {
            while (c.next()) {
               c.getAddedSubList().forEach(n -> bind(n.visibleProperty()));
               c.getRemoved().forEach(n -> unbind(n.visibleProperty())) ;
            }
        });

        bind(parentPane.getChildren());
    }

    @Override
    public boolean computeValue() {
        return parentPane.getChildren().stream()
            .filter(Node::isVisible)
            .findAny()
            .isPresent();
    }
}

parentPane.visibleProperty().bind(someVisibleChildren);