JavaFX Events Using Local Variables

Question

I have a method that creates an ImageView, called createImageView(), which uses EventHanlders to call vaious events. I would like to be able to use local variables in this method. What I usually do is assign final variables to use within the handle(Event) method.

In the method described below, when I go to use final I get the following errors:

The final local variable initY cannot be assigned, since it is defined in an enclosing type
The final local variable initY cannot be assigned, since it is defined in an enclosing type
The final local variable dragAnchor cannot be assigned, since it is defined in an enclosing type

Of course, removing final gives me this message:

Cannot refer to a non-final variable initX inside an inner class defined in a different method

So what do I have to do to make this method work?

private ImageView createImageView() {
    double initX;
    double initY;
    Point2D dragAnchor;

    imgView.setOnMousePressed(new EventHandler < MouseEvent > () {
        public void handle(MouseEvent me) {
            //when mouse is pressed, store initial position
            initX = imgView.getTranslateX();
            initY = imgView.getTranslateY();
            dragAnchor = new Point2D(me.getSceneX(), me.getSceneY());
            me.consume();
        }
    });

    imgView.setOnMouseDragged(new EventHandler < MouseEvent > () {
        public void handle(MouseEvent me) {
            double dragX = me.getSceneX() - dragAnchor.getX();
            double dragY = me.getSceneY() - dragAnchor.getY();

            double newXPosition = initX + dragX;
            double newYPosition = initY + dragY;
            imgView.setTranslateX(newXPosition);
            imgView.setTranslateY(newYPosition);
            me.consume();
        }
    });

    imgView.setOnMouseEntered(new EventHandler < MouseEvent > () {
        public void handle(MouseEvent event) {
            imgView.setEffect(new Glow(0.5));
            event.consume();
        }
    });

    imgView.setOnMouseExited(new EventHandler < MouseEvent > () {
        public void handle(MouseEvent event) {
            imgView.setEffect(new Glow(0.0));
            event.consume();
        }
    });
    return imgView;
}

jewelsea · Accepted Answer · 2013-04-13T17:48:24.600

1

Use JavaFX properties instead of primitive types.

For example:

final DoubleProperty initX = new SimpleDoubleProperty();
final ObjectProperty<Point2D> dragAnchor = new SimpleObjectProperty<>();
...
// in event handler
initX.set(
  imageView.getTranslateX()
);
dragAnchor.set(
  new Point2D(
    me.getSceneX(), 
    me.getSceneY()
  )
);

edited Apr 13 '13 at 17:48

answered Apr 13 '13 at 01:45

jewelsea

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Thanks jewelsea. This works great for doubles, but the dragAnchor still gives me the same problem. No biggie, my solution below seems to be working for now. – Matt Apr 13 '13 at 02:21
1

Updated example to show how you can use an `ObjectProperty` for the `dragAnchor`. – jewelsea Apr 13 '13 at 17:49

score 0 · Answer 2 · answered Apr 13 '13 at 00:43

0

I removed the 3 local variables and made them class variables and it worked. If anyone doesn't mind offering a quick explanation as of why I would appreciate it.

answered Apr 13 '13 at 00:43

Matt

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JavaFX Events Using Local Variables

2 Answers2