Detect if Java Swing component has been hidden

Question

Assume we have the following Swing application:

    final JFrame frame = new JFrame();

    final JPanel outer = new JPanel();
    frame.add(outer);

    JCompon         


        

Answer 1

To listen for this kind of events occuring in the hierarchy, you could do the following.

class SomeSpecialComponent extends JComponent implements HierarchyListener {

    private boolean amIVisible() {
        Container c = getParent();
        while (c != null)
            if (!c.isVisible())
                return false;
            else
                c = c.getParent();
        return true;
    }

    public void addNotify() {
        super.addNotify();
        addHierarchyListener(this);
    }

    public void removeNotify() {
        removeHierarchyListener(this);
        super.removeNotify();
    }

    public void hierarchyChanged(HierarchyEvent e) {
        System.out.println("Am I visible? " + amIVisible());
    }

}

You could even be more precise in the treatement of HierarchyEvents. Have a look at

http://java.sun.com/javase/6/docs/api/java/awt/event/HierarchyEvent.html