Why is the Circle hidden behind the Line?

Question

Yes, the title looks like the set up of a joke and yet it isn't.

The problem

I am writing a program using JavaFX. I add some drawings in a Pane (standard Line, Circle, Rectangle, and so on from javafx.scene.shape). I have set a onMouseEnter() on some circles to change their color. That works great, except when I place a line like in the image below:

The circle A changes color normally until I add the line B. When I hover the circle A then, nothing happens.

I figured out by testing that there was a problem when the circle was in the bounding box of the line (if the circle is halfway in the bounding box, the half that is out behaves correctly and the one inside doesn't).

Is it a normal behavious? What can I do to prevent it?

Partial code

In ConnectorWidget.java:

Circle circle = new Circle(...);
circle.setOnMouseEntered(event -> circle.setFill(Color.RED));
circle.setOnMouseExited(event -> circle.setFill(Color.WHITE));
getChildren().add(circle);

In TransistorWidget.java:

ConnectorWidget base = new ConnectorWidget(...);
getChildren().add(base);

In WireWidget:

Line line = new Line(...);
getChildren().add(line);

A new TransisorWidget can be added to the main pane on click.

A new WireWidget can be created in the main pane after a click on a ConnectorWidget followed by a click on another ConnectorWidget.

The rest of the code can be found on GitHub (permalink to the last commit I have when asking the question).

NOTE: To run the code from GitHub, you need this library.

The only way I can recreate that is if I call `line.setPickOnBounds(true);`. Did you have that set somewhere? — James_D, Oct 27 '16 at 16:26
Try to revers order of addition of the circle and the line, and you get opposite behavior. — talex, Oct 27 '16 at 16:26
@talex I can't, the line's coordinates depend on the circle coordinates. The circle must be added first. — SteeveDroz, Oct 27 '16 at 16:42
@SteeveDroz I assume he meant reverse in terms of the order in the `getChildren()` list, not first in terms of time. — James_D, Oct 27 '16 at 19:12

score 2 · Answer 1 · edited May 23 '17 at 10:34

2

You have already marked an answer as correct but I think this leads you in the wrong direction. It may solve your current problem but in general it will not always be possible to organize shapes in such a way.

James_D already metioned what is really going wrong here. This is described in detail in this post

edited May 23 '17 at 10:34

Community

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answered Oct 28 '16 at 07:23

mipa

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Actually i didn't even knew about `setPickOnBounds();` :). – GOXR3PLUS Oct 28 '16 at 10:43
Ok, I'm willing to change my answer to yours if you actually put the answer and not just a link to it. – SteeveDroz Oct 30 '16 at 06:26

score 1 · Accepted Answer · answered Oct 27 '16 at 21:04

Obviously it has to do with the fact that one Node overlays the other Node here.

Imagine that you are using StackPane as Layout.Adding first the Circle and then the Line,if the Line includes some pixels that the Circle already does then some parts of the Circle will not be visible.

Here i can imagine 3 possible solutions.

1)If you are using a Canvas , choose which is drawn first.The Circle or the Line?

2)If you are using some kind of Layout ,the you can play with getChilder.add/addAll methods.So you add first the Circle and then the Line as children to the Layout.

3 and better)

Using a StackPane you can add the children however you want.Then you can use already existing Node class methods(toFront(); and toBack();)

For example imagine that the Line is infront of the Circle, then call Circle.toFront(); and the Circle will come to front.

Well, I didn't think that would make a difference, thanks for the answer, it worked! — SteeveDroz, Oct 28 '16 at 05:19

Why is the Circle hidden behind the Line?

The problem

Partial code

2 Answers2