Pass mouse events to applications behind from a Java UI

Question

Hi, The question I have is exactly same in requirement as http://stackoverflow.com/questions/173579/how-to-pass-mouse-events-to-applications-behind-mine-in-c-vista , but I need the same for a Transparent Java UI. I can easily create a transparent Java UI using 6.0 but couldn't get any info about passing events through the app to any applications(say a browser) behind.

Answer 1

You could try using the Robot Class http://java.sun.com/javase/6/docs/api/java/awt/Robot.html which allows you to specify system events to the low level operating system, specifically things like mouse events.

Answer 2

I believe this will answer your question. To run it you will need Java 6 update 10 and above. I tested it on Windows Vista

import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class CickThrough {

    public static void main(String[] args) {
     JFrame.setDefaultLookAndFeelDecorated(true);
     JFrame f = new JFrame("Test");
     f.setAlwaysOnTop(true);
     Component c = new JPanel() {
      @Override
      public void paintComponent(Graphics g) {
       Graphics2D g2 = (Graphics2D)g.create();
       g2.setColor(Color.gray);
       int w = getWidth();
       int h = getHeight();
       g2.fillRect(0, 0, w,h);
       g2.setComposite(AlphaComposite.Clear);
       g2.fillRect(w/4, h/4, w-2*(w/4), h-2*(h/4));
      }
     };
     c.setPreferredSize(new Dimension(300, 300));
     f.getContentPane().add(c);
     f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     f.pack();
     f.setVisible(true);
     com.sun.awt.AWTUtilities.setWindowOpaque(f,false);
    }

}

Note that you need to either have an undecorated window or one that is decorated by Java alone (not the default OS decoration) otherwise the code won't work.