Mouse scrolling in Java FX

I want to use mouse scroll to make circle bigger (mouse-scroll-up) and circle smaller (mouse-scroll-down).

I have existing code to change circle radius smaller already with mouse middle button, but my question would be:

How can I use mouse-scroll-up and mouse-scroll-down to do the same thing?

I have googled, it could be done somehow with ScrollEvent, but I can’t understand this very well.

Answer

Answering to your question

How can I use mouse-scroll-up and mouse-scroll-down to do the same thing?

  • Use a ScrollListener on the circle and use the ScrollEvent reference to get the DeltaY.
  • Create a zoomfactor to calculate the zoom factor you want to have.
  • Apply this factor to the Scale property of your node.

Complete Example

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.input.ScrollEvent;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;

public class ZoomInOutCircles extends Application {

    @Override
    public void start(Stage primaryStage) {
        Group root = new Group();
        Scene scene = new Scene(root, 350, 300);
        primaryStage.setTitle("Dots");
        primaryStage.setScene(scene);

        Circle circle = new Circle(175, 150, 10, Color.BLUE);
        addMouseScrolling(circle);
        root.getChildren().add(circle);

        primaryStage.show();
    }

    public void addMouseScrolling(Node node) {
        node.setOnScroll((ScrollEvent event) -> {
            // Adjust the zoom factor as per your requirement
            double zoomFactor = 1.05;
            double deltaY = event.getDeltaY();
            if (deltaY < 0){
                zoomFactor = 2.0 - zoomFactor;
            }
            node.setScaleX(node.getScaleX() * zoomFactor);
            node.setScaleY(node.getScaleY() * zoomFactor);
        });
    }
}

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