how can I define a method for slider change in controller of a javaFX program? - slider

Question

I want to create a method in a controller of a fxml file, I want this method acts when the slider is changing.
I have a fxml file like this:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.Slider?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane prefHeight="150.0" prefWidth="200.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1">
<children>
<Slider fx:id="mySlider" blockIncrement="0.1" layoutX="26.0" layoutY="32.0" majorTickUnit="0.5" max="1.0" minorTickCount="1" showTickLabels="true" showTickMarks="true" />
<TextField fx:id="textField" layoutX="100.0" layoutY="99.0" prefHeight="25.0" prefWidth="75.0" />
<Label layoutX="43.0" layoutY="103.0" text="Label" />
</children>
</AnchorPane>
and I want to have a controller like this
package paper.view;
import javafx.fxml.FXML;
import javafx.scene.control.Slider;
import javafx.scene.control.TextField;
public class RootController
{
#FXML
private Slider mySlider;
#FXML
private TextField textField;
mySlider.valueProperty().addListener((observable, oldValue, newValue) -> {
textFieldOfEp.setText(Double.toString(newValue.doubleValue()) );
});
});
}
I want reflect the changes of slider in the textField.
like this picture:
How can I do this through a controller?
I don't want to do this in a start method of main class.
my start methos is like this:
public void start(Stage primaryStage) throws IOException
{
FXMLLoader loader=new FXMLLoader();
loader.setLocation(mainApp.class.getResource("view/Root.fxml"));
AnchorPane ap=loader.load();
Scene scene=new Scene(ap);
primaryStage.setScene(scene);
primaryStage.show();
}
the proposed answer worked.

Answer 1

You should register the listener in the controller's initialize() method:
package paper.view;
import javafx.fxml.FXML;
import javafx.scene.control.Slider;
import javafx.scene.control.TextField;
public class RootController
{
#FXML
private Slider mySlider;
#FXML
private TextField textField;
public void initialize() {
mySlider.valueProperty().addListener((observable, oldValue, newValue) -> {
textField.setText(Double.toString(newValue.intValue()));
});
}
}
and make sure you either specify the controller in the FXML file:
<AnchorPane fx:controller="paper.view.RootController" prefHeight="150.0" prefWidth="200.0" xmlns="http://javafx.com/javafx/8.0.65" xmlns:fx="http://javafx.com/fxml/1">
or set the controller on the FXMLLoader directly in code.
This will automatically update the text field when the intValue() of the slider's value changes:

Answer 2

I just accidentally found that property onValueChange does the trick, needing a ChangeListener<Number> signature for the handler (Double works too):
<Slider onValueChange="#doStuff"/>
#FXML
private void doStuff(ObservableValue<Number> ovn, Number before, Number after) {
System.out.println(before+" "+after);
}