Using javafx using circle.setCenterX and circle.setCenterY not working - javafx

Question

I am working through some coursework and am running into an odd issue. I'm working with javafx learning how to build shapes and work with alignment. Anyway my circle object will not respond to setCenterX or setCenterY commands (the radius definition statement does work) in the original definition statements nor in the commands issued by my event handlers which should be redefining these set x and set y values. I cannot figure out why. Please see my code below. When working correctly my code would allow me to move the circle object around the screen with the buttons and event handlers I've created. If I can figure out why the setCenterX and setCenterY don't work, I'm sure I can get the rest. Thanks for your help in advance.
package bravo15;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;
import javafx.scene.Scene;
public class FifteenDotThreeVersionThree extends Application {
#Override // Override the start method in the Application class
public void start(Stage primaryStage) {
Circle circle = new Circle();
circle.setCenterX(300);
circle.setCenterY(300);
circle.setRadius(50);
// Hold four buttons in an HBox
// Define hbox
HBox hBox = new HBox();
hBox.setSpacing(10);
hBox.setAlignment(Pos.CENTER);
// define buttons
Button btLeft = new Button("Left");
Button btRight = new Button("Right");
Button btUp = new Button("Up");
Button btDown = new Button("Down");
// add defined buttons into the hbox
hBox.getChildren().add(btLeft);
hBox.getChildren().add(btRight);
hBox.getChildren().add(btUp);
hBox.getChildren().add(btDown);
// Create and register the handlers for the four buttons
btLeft.setOnAction(e -> circle.setCenterX(circle.getCenterX() - 10));
btRight.setOnAction(e -> circle.setCenterX(circle.getCenterX() + 10));
btUp.setOnAction(e -> circle.setCenterY(circle.getCenterY() + 10));
btDown.setOnAction(e -> circle.setCenterY(circle.getCenterY() - 10));
BorderPane borderPane = new BorderPane();
borderPane.setTop(circle);
borderPane.setBottom(hBox);
BorderPane.setAlignment(hBox, Pos.CENTER);
// Create a scene and place it in the stage
Scene scene = new Scene(borderPane, 200, 200);
primaryStage.setTitle("ControlCircle Version 3"); // Set the stage title
primaryStage.setScene(scene); // Place the scene in the stage
primaryStage.show(); // Display the stage
}
/**
* The main method is only needed for the IDE with limited
* JavaFX support. Not needed for running from the command line.
*/
public static void main(String[] args) {
launch(args);
}
}

Answer 1

A BorderPane manages the layout of its components, so it positions the circle for you by setting its layoutX and layoutY properties so that it appears at the top left.
Wrap it in a Pane, which performs no layout, and place the Pane in the top of the border pane:
borderPane.setTop(new Pane(circle));
Note that you have things set up so that it is initially off-screen. You probably want to increase the size of the scene:
Scene scene = new Scene(borderPane, 600, 600);

Answer 2

You can do it this way to shift the circle:
btLeft.setOnAction(e -> circle.setTranslateX(circle.getTranslateX() - 10));
btRight.setOnAction(e -> circle.setTranslateX(circle.getTranslateX() + 10));
btUp.setOnAction(e -> circle.setTranslateY(circle.getTranslateY() - 10));
btDown.setOnAction(e -> circle.setTranslateY(circle.getTranslateY() + 10));
setTranslateX():
Defines the x coordinate of the translation that is added to this
Node's transform. The node's final translation will be computed as
layoutX + translateX, where layoutX establishes the node's stable
position and translateX optionally makes dynamic adjustments to that
position. This variable can be used to alter the location of a node
without disturbing its layoutBounds, which makes it useful for
animating a node's location.
And it looks better with borderPane.setCenter(circle); than borderPane.setTop(circle);.
I have also removed the following lines:
circle.setCenterX(300);
circle.setCenterY(300);