JavaFX Separator depend not on the Width of the Class - properties

Question

i would like to get a Separator, which changes his Size with the Size of the Mother-Component.
In my Example, i have a JavaFX Popup and there i add a VBox. To this VBox i add a HBox. And this HBox has a Label, a Speparator and a Button.
Now i would like to have that the Button is on the Right End and the Label is on the Left End of the HBox. I think i have to use a Separator between these components to get the Space.
How can i handle it...
I made something like this, but it does not work.
// Box for the Headline
HBox headLine = new HBox();
headLine.setPadding(new Insets(5, 5, 5, 5));
// Label with the HeadLine Description in
final Label heading = new Label(headLineText);
heading.getStyleClass().addAll("popup-label-name");
// Close Button
close = new Button("X");
close.setVisible(false);
closeButtonHandler();
// Creates an invisble Separator1
Separator sep = new Separator(Orientation.HORIZONTAL);
sep.setVisible(false);
sep.widthProperty().add(m_container.widthProperty().get());
close.getStyleClass().addAll("popup-button", "popup-button-color");
// Adds to the Headline the Data
headLine.getChildren().addAll(heading, sep, close);
The Variable m_container is the VBox! How can i handle it?
Thanks for your help :)

Answer 1

The simplest way (if not using a different container like AnchorPane) is to insert an invisible, but expandible 'space' object:
void testLabelSpace(HBox box) {
Text first = new Text("first");
Text second = new Text("second");
Node space = new HBox();
HBox.setHgrow(space, Priority.ALWAYS);
box.getChildren().addAll(first, space, second);
}

Answer 2

If I understand the question correctly, you just want blank space between the label and the button. Just tell the Label always to grow horizontally, and set its maximum width to allow it to grow to any size:
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.stage.Stage;
public class HBoxExample extends Application {
#Override
public void start(Stage primaryStage) {
HBox hbox = new HBox();
Label label = new Label("Label");
Button button = new Button("Button");
HBox.setHgrow(label, Priority.ALWAYS);
label.setMaxWidth(Double.MAX_VALUE);
hbox.getChildren().addAll(label, button);
primaryStage.setScene(new Scene(hbox, 350, 75));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}