JavaFX - Get Actual Computed-Size of HBOX - javafx

Question

I have a simple HBOX control which uses USE_COMPUTED_SIZE in Pref-Height, hence the size is all calculated and adjusted by the controls inside, which are a couple VBOX.
The issue comes when I try to add a new Pane as a children to the HBOX and draw a vertical line from top to bottom of the HBOX, so I write my line:
int startX = 5;
int startY = 0;
int endX = 5;
Line line = new Line(startX,startY,endX,hbox.getHeight());
Here, I need the hbox.getHeight(), but surprise: it is =-1, because it is using USE_COMPUTED_SIZE. So, how can I get the real (computed) value of hbox.getHeight()?

Answer 1

Not tested, but I think you can do something like:
public class HBoxWithLine extends HBox {
// Example of configurable property:
private final DoubleProperty lineOffset = new SimpleDoubleProperty(5);
public DoubleProperty lineOffsetProperty() {
return lineOffset ;
}
public final double getLineOffset() {
return lineOffsetProperty().get();
}
public final void setLineOffset(double lineOffset) {
lineOffsetProperty().set(lineOffset);
}
private final Line line = new Line();
public HBoxWithLine() {
getChildren().add(line);
// request layout when offset is invalidated:
lineOffset.addListener(obs -> requestLayout());
}
#Override
protected void layoutChildren() {
line.setStartX(getLineOffset());
line.setEndX(getLineOffset());
line.setStartY(0);
line.setEndY(getHeight());
super.layoutChildren();
}
}
Now you can just create a HBoxWithLine and add (additional) child nodes to it, set it's pref width and height to either fixed values, or Region.USE_COMPUTED_SIZE, etc., and it should just work.