Question

I’ve been experimenting around with JavaFX and I was looking to perform some operations on the substructure of a Slider, such as get the size and position of the thumb, fire off my own mouse-over events, etc, without having to extrapolate that information based on the position and value of the slider itself. Is it possible to programmatically access this substructure and glean some basic information about it?

Answer 1

Slider is a regular JavaFX Node, so you can traverse rendering tree for it. Subnodes can be identified, for example, by styleClass. See next example, which prints Slider structure.
From Node with style-class “thumb” you can get screen position of thumb.

public class DoSlider extends Application {
@Override
public void start(Stage stage) {
    Slider slider = SliderBuilder.create().min(0).max(100).value(50).showTickLabels(true).showTickMarks(true).build();

    stage.setScene(new Scene(new Group(slider)));
    stage.show();

    traverse(slider);
}

public void traverse(Parent node) {
    for (Node subNode : node.getChildrenUnmodifiable()) {
        System.out.println(subNode.getClass().getSimpleName() + " " + subNode.getStyleClass());
        if (subNode instanceof Parent) {
            traverse((Parent)subNode);
        }
    }
}

public static void main(String[] args) {
    launch(DoSlider.class, args);
}

Output will be next:

SliderSkin slider
NumberAxis axis
Label label axis-label
LabelSkin label axis-label
Text 
Path axis-tick-mark
Path axis-minor-tick-mark
Text tick-mark
Text tick-mark
Text tick-mark
Text tick-mark
Text tick-mark
StackPane track
StackPane thumb