How to set Axis range in Java FX using SampleController?

Question

I have created an fxml layout using scene builder v2.0. I am modifying the chart in the controller file i.e, SampleController.java file. I was able to set the chart title using .setTitle method. I need to set the range of xAxis (Start, End, Ticks) and yAxis dynamically. In CSS it is easy to set using lowerBound and upperBound Property. But it is a permanent solution. Please provide your valuable suggestions and solutions.

Main.java:

package application;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.SplitPane;
import javafx.stage.Stage;
public class Main extends Application{
    @Override
    public void start(Stage primaryStage) { 
        try {
            SplitPane root = (SplitPane)FXMLLoader.load(getClass().getResource("Sample.fxml"));
            Scene scene = new Scene(root,800,400);          
            scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
            primaryStage.setScene(scene);
            primaryStage.show();            
        } catch(Exception e) {
            e.printStackTrace();
        }
    }   
    public static void main(String[] args) {
        launch(args);



    }
}

Sample.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.chart.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.BorderPane?>

<SplitPane dividerPositions="0.7892976588628763" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="400.0" minWidth="800.0" prefHeight="400.0" prefWidth="800.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="application.SampleController">
  <items>
    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="160.0" prefWidth="100.0">
         <children>
            <LineChart fx:id="Ch" alternativeColumnFillVisible="true" layoutX="14.0" prefHeight="398.0" prefWidth="500.0">
              <xAxis>
                <NumberAxis side="BOTTOM" />
              </xAxis>
              <yAxis>
                <NumberAxis layoutX="10.0" side="LEFT" />
              </yAxis>
            </LineChart>
         </children></AnchorPane>
    <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="160.0" prefWidth="100.0">
         <children>
            <Button fx:id="sine" layoutX="21.0" layoutY="101.0" mnemonicParsing="false" text="Sinusoidal" />
            <Button fx:id="triangle" layoutX="21.0" layoutY="148.0" mnemonicParsing="false" prefHeight="25.0" prefWidth="70.0" text="Triangle" />
            <Button fx:id="square" layoutX="21.0" layoutY="187.0" mnemonicParsing="false" prefHeight="25.0" prefWidth="70.0" text="Square" />
            <Label layoutX="20.0" layoutY="40.0" prefHeight="17.0" prefWidth="83.0" text="Controls" />
         </children></AnchorPane>
  </items>
</SplitPane>

SampleController.java

package application;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.chart.Axis;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.scene.chart.XYChart.Series;
import javafx.scene.control.Button;
import javafx.util.Duration;


public class SampleController implements Initializable {

     final NumberAxis xAxis = new NumberAxis(0,24,3);

     final NumberAxis yAxis = new NumberAxis(0,1,0.1);

    @FXML //  fx:id="Ch"
    private LineChart<Number, Number> Ch= new LineChart<>(xAxis, yAxis); // No use of using a constructor.
    @FXML//  fx:id="sine"
    private Button sine; // Value injected by FXMLLoader
    @FXML//  fx:id="triangle"
    private Button triangle; // Value injected by FXMLLoader
    @FXML//  fx:id="Square"
    private Button square; // Value injected by FXMLLoader




    @Override // This method is called by the FXMLLoader when initialization is complete
    public void initialize(URL fxmlFileLocation, ResourceBundle resources) {
        assert Ch != null : "fx:id=\"Ch\" was not injected: check your FXML file 'sample.fxml'.";

        // initialize your logic here: all @FXML variables will have been injected
        sine.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                System.out.println("Sinusoidal Signal Selected /n/n");
            }
        });

        triangle.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                System.out.println("Triangle Signal Selected /n/n");
            }
        });

        square.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                System.out.println("Square Signal Selected /n/n");
            }
        });



        //Ch = new LineChart<>(xAxis, yAxis); // This sadly loads a new chart but is not visible

        Ch.setTitle("PiScope Demo");

        //Need to set xAxis range Dynamically

        //Need to set yAxis range Dynamically

        /*
         * In CSS we can use lowerBound and upperBound Property.
         *          */     

    }
}

Answer 1

Inject the axes into the controller:

        <LineChart fx:id="Ch" alternativeColumnFillVisible="true" layoutX="14.0" prefHeight="398.0" prefWidth="500.0">
          <xAxis>
            <NumberAxis side="BOTTOM" fx:id="xAxis" />
          </xAxis>
          <yAxis>
            <NumberAxis layoutX="10.0" side="LEFT" fx:id="yAxis" />
          </yAxis>
        </LineChart>

and

public class SampleController implements Initializable {

    @FXML
    private NumberAxis xAxis ;

    @FXML
    private NumberAxis yAxis ;

    // never initialize fields that are injected by @FXML:
    // they are initialized by the FXMLLoader
    @FXML //  fx:id="Ch"
    private LineChart<Number, Number> Ch ;

    // ...
}

Then you can just set the range in the initialize() method:

public void initialize() {

    // ...

    xAxis.setAutoRanging(false);
    xAxis.setLowerBound(0);
    xAxis.setUpperBound(24);
    xAxis.setTickUnit(3);

    yAxis.setAutoRanging(false);
    yAxis.setLowerBound(0);
    yAxis.setUpperBound(1);
    yAxis.setTickUnit(0.1);

    // ...
}

Answer 2

There are several flavors of "axis" relevant to the javafx chart. I found that the LineChart initialization in fxml resulted in Axis< Number >. The Axis< T > class does not have set methods for lower and upper bounds. So I found a solution by casting explicitly to NumberAxis which does have these set methods.

public void setAxisBounds(LineChart<Number, Number> myChart, double min, double max, boolean isXAxis) {
    NumberAxis axis;
    if (isXAxis)
        axis=(NumberAxis) myChart.getXAxis();
    else
        axis=(NumberAxis) myChart.getYAxis();
    axis.setAutoRanging(false);
    axis.setLowerBound(min);
    axis.setUpperBound(max);
}