Updating a textField when size of shape changes - JavaFX - javafx

Question

Suppose I have the following:
Creating A Rectangle(With A Top Left Handler):
public Group createDraggableRectangle(double x, double y, double width, double height) {
final double handleRadius = 20 ;
final double handleRadius2 = 30 ;
Rectangle rect = new Rectangle(x, y, width, height);
// top left resize handle:
Circle resizeHandleNW = new Circle(handleRadius, Color.RED);
resizeHandleNW.setOpacity(0);
// bind to top left cornerof Rectangle:
resizeHandleNW.centerXProperty().bind(rect.xProperty());
resizeHandleNW.centerYProperty().bind(rect.yProperty());
resizeHandleNW.setStyle("-fx-cursor: NW_RESIZE; ");
Group group = new Group(rect, resizeHandleNW);
Wrapper<Point2D> mouseLocation = new Wrapper<>();
setUpDragging(resizeHandleNW, mouseLocation) ;
resizeHandleNW.setOnMouseDragged(event -> {
if (mouseLocation.value != null) {
double deltaX = event.getSceneX() - mouseLocation.value.getX();
double deltaY = event.getSceneY() - mouseLocation.value.getY();
double newX = rect.getX() + deltaX ;
if (newX >= handleRadius
&& newX <= rect.getX() + rect.getWidth() - handleRadius) {
rect.setX(newX);
rect.setWidth(rect.getWidth() - deltaX);
}
double newY = rect.getY() + deltaY ;
if (newY >= handleRadius
&& newY <= rect.getY() + rect.getHeight() - handleRadius) {
rect.setY(newY);
rect.setHeight(rect.getHeight() - deltaY);
}
mouseLocation.value = new Point2D(event.getSceneX(), event.getSceneY());
}
return group;
});
Controller Class(Method For Selecting Object):
#FXML
private TextField heightField;
if (!selectedShapes.contains(shape)) {
shape.setStyle("-fx-effect: dropshadow(three-pass-box, #cece02, 6, 6, 0, 0);");
selectedShapes.add(shape);
rotate.setDisable(false);
deletebutton.setDisable(false);
}
I know that writing System.out.println(rect.getHeight()) in the Rectangle class will give me the height every-time the size is changed.
However my question is that how would I add this value to the textField, held in my controller class? I have tried various ways, however I keep getting a null pointer exception.
Thanks

Answer 1

Somewhere you presumably do
Group draggableRect = createDraggableRectangle(...);
So then you just do
heightField.textProperty().bind(Bindings.createStringBinding(
() -> String.format("%.1f", draggableRect.getBoundsInLocal().getHeight()),
draggableRect.boundsInLocalProperty());
or, if you want the height field's text to change in other ways (e.g. if it is editable),
draggableRect.boundsInLocalProperty().addListener((obs, oldBounds, newBounds) ->
heightField.setText(String.format("%.1f", newBounds.getHeight())));