JavaFX Slider : How to drag the thumb only by increments - javafx

Question

I am trying to implement the Slider such that user can drag only by given increments. I tried in different ways by using the Slider API, but didnt get the desired results. Below is a quick demo of what I had tried. I am expecting to drag the thumb only in increments of 10 not with intermediate values. snapToTicks is doing what I required, but only after finishing the drag. I am trying to not move the thumb till the next desired block increment is reached.
Can anyone let me know how can i achieve this. Below is the screenshot while dragging.
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.Slider;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class SliderDemo extends Application {
public static void main(String... args){
Application.launch(args);
}
#Override
public void start(Stage stage) throws Exception {
Label label = new Label();
label.setStyle("-fx-font-size:30px");
Slider slider = new Slider(5,240,5);
slider.setBlockIncrement(10);
slider.setMajorTickUnit(10);
slider.setMinorTickCount(0);
slider.setShowTickLabels(true);
slider.setShowTickMarks(true);
slider.setSnapToTicks(true);
slider.valueProperty().addListener((obs,old,val)->label.setText((int)Math.round(val.doubleValue())+""));
VBox root = new VBox(slider,label);
root.setAlignment(Pos.CENTER);
root.setPadding(new Insets(20));
root.setSpacing(20);
Scene scene = new Scene(root,600,200);
stage.setScene(scene);
stage.show();
}
}

Answer 1

The solution is to set the value of the slider directly inside of the listener. The listener will not be called again
final ChangeListener<Number> numberChangeListener = (obs, old, val) -> {
final double roundedValue = Math.floor(val.doubleValue() / 10.0) * 10.0;
slider.valueProperty().set(roundedValue);
label.setText(Double.toString(roundedValue));
};
slider.valueProperty().addListener(numberChangeListener);
If you use Math.floor() instead of round you get a more intuatuive behavior of the thumb.