How do I fix aligning issues when using JFXPanel?

Question

My problem is, that i have a normal JavaFX fxml file, which automatically realigns its elements when i start it normally and resize it. But i when i start it with the JFXPanel suddenly nothing realigns anymore. And i have no idea what the reason could be. (I have to use this method to start my gui, there is no other way)

My code:

final JFXPanel panel = new JFXPanel();
panel.addComponentListener(new ComponentAdapter() {
    @Override
    public void componentResized(ComponentEvent e) {
        super.componentResized(e);
        // Maybe here some code?
    }
});

JFrame frame = new JFrame();

Platform.runLater(() -> {
    try {
        Group root = new Group();
        Scene scene = new Scene(root);

        FXMLLoader loader = new FXMLLoader(getClass().getResource("myGui.fxml"));
        Node node = loader.load();

        root.getChildren().add(node);
        panel.setScene(scene);
    } catch (IOException e) {
        e.printStackTrace();
    }
});

frame.add(panel);
frame.pack();
frame.setVisible(true);

I researched for hours and don't really find a solution to my problem. Maybe i searched wrong? i would be really grateful if someone could help me.

Im a bit suspicious with the Group object "root" but i have no clue what it does. (I have this code from a website, because im inexperienced with JFXPanels so im not entirely sure what every line does)

My whole class:

public class Test {
    public static void main(String[] args) {
        Test test = new Test();
        test.startGui();
    }

    public void startGui() {
        final JFXPanel panel = new JFXPanel();
        panel.setPreferredSize(new Dimension(600, 400));
        panel.addComponentListener(new ComponentAdapter() {
            @Override
            public void componentResized(ComponentEvent e) {
                super.componentResized(e);
                // Maybe here some code?
            }
        });

        JFrame frame = new JFrame();

        Platform.runLater(() -> {
            try {
                Group root = new Group();
                Scene scene = new Scene(root);

                FXMLLoader loader = new FXMLLoader(getClass().getResource("myGui.fxml"));
                Node node = loader.load();

                root.getChildren().add(node);
                panel.setScene(scene);
            } catch (IOException e) {
                e.printStackTrace();
            }
        });

        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }
}

And my fxml file

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Label?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.layout.StackPane?>


<HBox maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/10.0.1" xmlns:fx="http://javafx.com/fxml/1">
   <children>
      <StackPane prefHeight="150.0" prefWidth="200.0" HBox.hgrow="ALWAYS">
         <children>
            <Label text="left" />
         </children>
      </StackPane>
      <StackPane prefHeight="150.0" prefWidth="200.0" HBox.hgrow="ALWAYS">
         <children>
            <Label text="right" />
         </children>
      </StackPane>
   </children>
</HBox>

When you start the gui and resize it the left and right label should go further away. They should have the same distance to the borders of the gui.

Answer 1

You are adding the JFXPanel to a JFrame which uses BorderLayout by default.
To change the resizing and positioning of the JFXPanel set other layout manager.
For example:

frame.setLayout(new GridBagLayout());