JavaFX 2.0 - How to change legend color of a LineChart dynamically?

Question

I am trying to style my JavaFX linechart but I have some trouble with the legend.

I know how to change the legend color of a line chart in the css file:

Answer 1

It seems that this guy is able to lookup the nodes used for legend using their class, and then calling setStyle() on those nodes. (I don't think his problem is relevant for yours)

Answer 2

For future reference, this problem can be solved by wrapping your relevant code in a call to Platform.runLater(). For example:

LineChart<Number, Number> plot;
....
Platform.runLater(() -> {
    Node nl = plot.lookup(".default-color0.chart-series-line");
    Node ns = plot.lookup(".default-color0.chart-line-symbol");

    nl.setStyle("-fx-stroke: #333;");
    ns.setStyle("-fx-background-color: #333, white;");
}); 

Answer 3

I ran into this issue as well. The issue seems to be that when data series are added to the chart, the legend isn't updated at the same time, so when you lookup components with that seriesN style class they don't exist yet. Came up with a work-around that detects when the legend items are created so that dynamic styling can be added to them.

I added a ListChangeListener to the chart legend's "getChildrenUnmodifiable()" ObservableList, which in turn adds a ListChangeListener to each of the legend's children as they get added. From within this listener, we can tell when new items are being added to the legend (or removed). This allow us to then make the dynamic style changes.

for (Node n : lineChart.getChildrenUnmodifiable())
    {
        if (n instanceof Legend)
        {
            final Legend legend = (Legend) n;

            // remove the legend
            legend.getChildrenUnmodifiable().addListener(new ListChangeListener<Object>()
            {
                @Override
                public void onChanged(Change<?> arg0)
                {
                    for (Node node : legend.getChildrenUnmodifiable())
                    {
                        if (node instanceof Label)
                        {
                            final Label label = (Label) node;
                            label.getChildrenUnmodifiable().addListener(new ListChangeListener<Object>()
                            {
                                @Override
                                public void onChanged(Change<?> arg0)
                                {
                                    //make style changes here
                                }

                            });
                        }
                    }
                }
            });
        }
    }

Answer 4

This solution is based on @Chris' solution

 if (checkCombo.getCheckModel().isChecked(0)) {
    lineChart.getData().add(seriesTest1);
    changeColorSeries(lineChart.getData().size() - 1, "darkgreen");
 }

 if (checkCombo.getCheckModel().isChecked(3)) {
    lineChart.getData().add(seriesTest2);
    changeColorSeries(lineChart.getData().size() - 1, "darkred");
 }

 private void changeColor(int position, String color) {
        Platform.runLater(() -> {
            Node nl = lineChart.lookup(".default-color" + position + ".chart-series-line");
            Node ns = lineChart.lookup(".default-color" + position + ".chart-line-symbol");
            Node nsl = lineChart.lookup(".default-color" + position + ".chart-legend-item-symbol");

            nl.setStyle("-fx-stroke: " + color + ";");
            ns.setStyle("-fx-background-color: " + color + ", white;");
            nsl.setStyle("-fx-background-color: " + color + ", white;");
        });
 }