JavaFX cannot draw line in BarChart - javafx

Question

I want a draw a line in a Barchart. the line reflects a certain value to which other values are compared. I applied the solution for a LineChart to my situation (see code). However, no line is drawn.
public XYChart buildBarChart ()
{
Line valueMarker = new Line ();
CategoryAxis xAxis = new CategoryAxis();
NumberAxis yAxis = new NumberAxis();
BarChart<String,Number> barChart = new BarChart<String,Number> (xAxis,yAxis);
barChart.setBarGap (-10);
barChart.setCategoryGap (0);
barChart.getYAxis().setTickLabelsVisible(false);
barChart.getYAxis().setOpacity(0);
yAxis.setLabel ("Score");
// update marker
Node chartArea = barChart.lookup (".chart-plot-background");
Bounds chartAreaBounds = chartArea.localToScene (chartArea.getBoundsInLocal ());
// remember scene position of chart area
yShift = chartAreaBounds.getMinY();
// set x parameters of the valueMarker to chart area bounds
valueMarker.setStartX (chartAreaBounds.getMinX());
valueMarker.setEndX (chartAreaBounds.getMaxX());
// find pixel position of that value
double displayPosition = yAxis.getDisplayPosition (valNederland);
// update marker
valueMarker.setStartY (yShift + displayPosition);
valueMarker.setEndY (yShift + displayPosition);
BarChart.Series<String,Number> series1 = new BarChart.Series<String,Number> ();
BarChart.Series<String,Number> series2 = new BarChart.Series<String,Number> ();
BarChart.Series<String,Number> series3 = new BarChart.Series<String,Number> ();
BarChart.Series<String,Number> series4 = new BarChart.Series<String,Number> ();
series1.getData ().add (new XYChart.Data<String,Number> (sRegio, valRegio_2015));
series2.getData ().add (new XYChart.Data<String,Number> (sOmgeving, valOmgeving));
series3.getData ().add (new XYChart.Data<String,Number> (sRest, valRest));
series4.getData ().add (new XYChart.Data<String,Number> (sNl, valNederland));
barChart.getData().addAll (series1, series2, series3, series4);
return barChart;
} /*** buildBarChart ***/
Essential for this situation is to have the coordinates of the ChartArea. When I inspect the properties of ChartArea in the debugger I find that all values of _geomBounds are 'unlogic', i.e. maxX/Y = -1 and minX/Y = -1. I inspect just one line after chartASreaBounds is assigned a value.
To me it seems that the barChart lookup fails as I had a similar problem before. Does anyone have a suggestion of how to correct this situation?
Edit
The BarChart is created in the constructor as follows:
public Charter (int nTimes, int nCategories, float [] years, String [] titles, String label, Indicator ind, float [] past)
{
this ();
// all kind of code to do somethong with the parameters omitted
// ...
// Setting up the BarChart. Note that past == null in my experiments
HBox hBox = new HBox ();
XYChart bar = buildBarChart ();
bar.setPrefHeight (height);
bar.setPrefWidth (width);
VBox buttons = buildButtonView ();
if (past != null)
{
XYChart line = buildLineChart ();
line.setPrefHeight (height);
line.setPrefWidth (width);
hBox.getChildren ().addAll (bar, line);
} else
{
hBox.getChildren ().addAll (bar);
} // if
Label dsecription = new Label (label);
this.getProperties ().put ("--Indicator", ind.getName ());
this.getChildren ().addAll (dsecription, hBox);
} /*** Charter ***/
After a Charter has been created it is added to the VBox and therewith shows on the screen as VBox is already added to the scene.

Answer 1

It looks like you want to calculate the position of the bar chart on the screen before it is added to the scene. Since at that point it is not yet on the screen that position is -1 or not defined.
I tend to make my layouts in fxml, therefore such problems don't appear. If you need to do it in code, I think first adding it to the children of hBox before drawing the line could solve the issue.