If I set the stage's dimensions then show it, the controls and layouts are sized appropriately to fit it.

But if I switch the scene later, the new scene's layouts are sized at their defaults instead of the stage's current dimensions. If I resize the window with the mouse after switching the scene, the layout ends up getting adjusted to the stage's new dimensions accordingly. This seems a little inconsistent.

The application below demonstrates this if you click the button to switch the scene:

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextArea;
import javafx.scene.layout.BorderPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

/**
 *
 *
 */
public class Main extends Application {
    
    @Override
    public void start(final Stage primaryStage) {
        BorderPane root = new BorderPane();
        
        //Top of the scene.
        Button button = new Button("Click Me!");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent t) {
                BorderPane root = new BorderPane();
                TextArea textArea = new TextArea();
                textArea.setText("Hello World!");
                root.setCenter(textArea);
                
                Scene scene = new Scene(root);
                scene.setFill(Color.AQUA);
                primaryStage.setScene(scene);
            }
        });
        root.setTop(button);
        
        //Middle.
        TextArea textArea = new TextArea();
        textArea.setText("Hello World!");
        root.setCenter(textArea);
        
        Scene scene = new Scene(root, 300, 250);
        
        primaryStage.setTitle("Hello World!");
        primaryStage.setScene(scene);
        primaryStage.setWidth(500);
        primaryStage.setHeight(300);
        primaryStage.show();
    }

    /**
     * The main() method is ignored in correctly deployed JavaFX application.
     * main() serves only as fallback in case the application can not be
     * launched through deployment artifacts, e.g., in IDEs with limited FX
     * support. NetBeans ignores main().
     *
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }
}