Adding listeners in Netbeans

Question

My question is very simple: I'm trying to add a WindowListener and an onClose Listener (or Listener in general), but what I don't know how to do is where to add the code in Netbeans 8.0.

I have this doubt because Netbeans creates the JFrame entirely by itself, and hides that code. I have to add the Listener somewhere in this custom code created by Netbeans or in the Class Constructor, or any other place?

Answer 1

You can add many listeners to the JFrame using JFrame's Properties -> Events and Properties (Bindings can help you sometimes too).

If you don't get what you need, just place your code into the constructor or - if it's a lot - make private method you call in the ctor.

I mostly prefer a private method than putting all into ctor, but that's really something of your choice.

Example:

public class Example extends javax.swing.JFrame
{
    public Example()
    {
        initComponents(); // This is generated by NB - do NOT remove!

        addListeners(); // add listeners here
    }


    /**
     * Adds listeners to the frame
     */ 
    private void addListeners()
    {
        // Add your listeners here as usual
        this.addWindowListener(new WindowListener()
        {
            @Override
            public void windowOpened(WindowEvent e)
            {
                /* ... */
            }

            /* Other methods of WindowListener ... */
        });
    }

    /* ... */
}

Just one thing here: Add your listeners after initComponents() - that's the generated method witch initializes all components - otherwise some components may not be ready.