JavaFX LineChart: Insert new data in the middle of the chart

Question

I'm using a line chart with JavaFX:

LineChart<Number, Number> lineChart = new LineChart<>(xAxis, yAxis);

XYChart.Series series = new XYChart.Series();

lineChart.getData().add(series);

I want to add data to the series successively, thereby the order in which the values arrive can not be predicted. For example, the index can be between 0 and the current size of the series.

series.getData().add(new XYChart.Data(index, value));

Consider the following scenario:

//initializing...
series.getData().add(new XYChart.Data(1, 400));
series.getData().add(new XYChart.Data(3, 500));
series.getData().add(new XYChart.Data(8, 100));
series.getData().add(new XYChart.Data(12, 120));
series.getData().add(new XYChart.Data(20, 300));

//later...
series.getData().add(new XYChart.Data(2, 450));
series.getData().add(new XYChart.Data(5, 300));
series.getData().add(new XYChart.Data(15, 200));

The problem is how the graph is depicted. In the example above, at index 20 the graph makes a loop back to index 2. It looks like this:

But I want it to look like this:

What settings are necessary to update the graph properly without additional lines crossing the graph?

Answer 1

I do something like this (my data is string, number). I can't help but thinking there must be a better way. I've put this all in a method so I can just call addSorted(series,newData);

final Comparator<XYChart.Data<String, Number>> comparator = 
        (XYChart.Data<String, Number> o1, XYChart.Data<String, Number> o2) -> 
                o1.getXValue().compareTo(o2.getXValue());
lineChart.getData().get(0).getData().add(new XYChart.Data<>("2020", 1));
XYChart.Series newSeries = new XYChart.Series(lineChart.getData().get(0).getData().sorted(comparator));
lineChart.getData().add(0,newSeries);

Answer 2

There is a new answer to this problem with JavaFX 9.

If you have JDK9, try

lineChart.setAxisSortingPolicy(LineChart.SortingPolicy.X_AXIS);

(this is the default setting for JavaFX 9)

If you want for data to be plotted in the order it was added use:

lineChart.setAxisSortingPolicy(LineChart.SortingPolicy.NONE);

See information here: http://download.java.net/jdk9/jfxdocs/javafx/scene/chart/LineChart.html#axisSortingPolicyProperty