Reduce number of tick labels on JavaFX xAxis

Question

Up from a certain number of plotted ticks the labels on the xAxis are rotated by 90 degrees into a vertical position. I would like to keep them horizontal and only plot as many as are fitting to the xAxis.

This shows how it looks and how I would like it to look:

sample image

Trying xAxis.setTickLabelRotation() is not showing any effect if there is not enough space to rotate the labels it seems.

I did a work around hiding the xAxis labels, positioning a HBox below the chart and fill it with a few labels that are horizontal. But that is no clean solution and did lead to other issues I would like to avoid.

This example:

JavaFX manually set NumberAxis ticks

shows how to subclass a NumberAxis but I did not make it yet to transfer that to achieve my goal. My idea is to subclass the NumberAxis, overwrite the methods that are responsible for plotting the labels on the xAxis and use a formatter that turns the numbers into the date format to be plotted.

Would that be the right approach and what would be the methods to address? I spent a lot of time going through the sources without success. Any hint into the right direction would be highly appreciated.

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;


public class LineChartSample extends Application {

    @Override
    public void start(Stage stage) {

        final CategoryAxis xAxis = new CategoryAxis();
        final NumberAxis yAxis = new NumberAxis();
        final LineChart<String, Number> lineChart = new LineChart<String, Number>(xAxis, yAxis);
        lineChart.setAnimated(false);
        lineChart.setCreateSymbols(false);
        XYChart.Series series = new XYChart.Series();

        for (int i = 0; i < 100; i+=1)
            series.getData().add(new XYChart.Data(msToDateString(i), Math.random()));


        Scene scene = new Scene(lineChart, 800, 150);
        lineChart.getData().add(series);

        stage.setScene(scene);
        stage.show();
    }

    //msToDateString-----------------------------------------------------------------
    private static DateFormat df = new SimpleDateFormat("yyyy.MM.dd HH:mm:ss.SSS");
    private static Date result = new Date();

    public static String msToDateString(long milliseconds) {
        result.setTime(milliseconds);
        return df.format(result);
    }

    public static void main(String[] args) {
        launch(args);
    }
}

config control of the ticks is rather .. basic (very near to not available at all ;) Though, here it looks like it might be a problem of using a Category axis - how should it know the items to leave out? And that usage seems to wrong: what you might be a real Date/Time Axis with the notion of continuety - which you might implement yourself and/or search for examples out in the wild (and enhance if needed) — kleopatra, Sep 21 '21 at 16:03

score 0 · Answer 1 · answered Sep 21 '22 at 11:04

I know this is an old topic now, but I came across this question while trying to deal with the similar problem myself. I was using custom LineChart class (extended) and had to override layoutPlotChildren() method to be able to put additional shapes to the plot list. To make graph more readable, I wanted to show every second tick on the X axis. In the end, I solved this problem by iterating tick marks and making every second mark invisible. Here is the snippet of the code:

 public class MyLineChart extends LineChart<String, Double> {

 public MyLineChart (
        @NamedArg("xAxis") final Axis<String> xAxis,
        @NamedArg("yAxis") final Axis<Double> yAxis) {

    super(xAxis, yAxis);
 }

 ...

 @Override
 protected void layoutPlotChildren() {
    super.layoutPlotChildren();
    ...
    
    ObservableList<Axis.TickMark<String>> tickMarks = getXAxis().getTickMarks();
    for (int i = 0; i < tickMarks.size(); i++) {
        tickMarks.get(i).setTextVisible(i % 2 == 0);
    }
 }

Hope this helps...

Reduce number of tick labels on JavaFX xAxis

1 Answers1