Question

btnnew.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent e) {
            try {
                System.out.println("Hello");
                packetListener.listener();
            } catch (Exception e1) {
                // TODO Auto-generated catch block
                e1.printStackTrace();
            }
        }
    });

I get a black screen when it runs. But when the packetListener.listener(); calls in the constructor it shows.

Can you please explain why this is happening?

Answer 1

I think the packetListener.listener(); method performs some complex operation which blocks your UI.

Better create a thread for listening the packet.
ie,use it like this

 try {
    System.out.println("Hello");
    new Thread(new Runnable() {
        public void run() {
packetListener.listener();
            }
    }).start();         

        } catch (Exception e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

Hope this helps you