Java trackpad 2-finger scroll listener

Question

how can i detect a 2-finger scroll on a laptop trackpad in java? I've been searching google and here but can't find anything on scrolling using a trackpad let alone how to listen for it. any help would be greatly appreciated. thanks.

Answer 1

I made this sample program

import java.awt.event.MouseWheelEvent;
import java.awt.event.MouseWheelListener;

import javax.swing.JFrame;

public class ScrollTest {

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(200,200);
        frame.addMouseWheelListener(new MouseWheelListener() {

            @Override
            public void mouseWheelMoved(MouseWheelEvent event) {
                if (event.isShiftDown()) {
                    System.err.println("Horizontal " + event.getWheelRotation());
                } else {
                    System.err.println("Vertical " + event.getWheelRotation());                    
                }
            }
        });
        frame.setVisible(true);
    }
}

It will print if the scroll is horizontal or vertical and how much the scroll was when you scroll within the opened window on a mac with a touchpad.