Listening to key events for a component hierarchy

Question

I have a Swing app that needs to display different sets of controls based on whether the control or alt keys are pressed. I added a KeyListener to the main component, but i

Answer 1

You may consider using the InputMap and ActionMap of some swing components. You can specify with JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT to indicate you want to respond to the given keystroke when either the component or its subcomponents are in focus.

If you don't want to use the InputMap or ActionMap, you could just add the KeyListener to all the child components:

for (Component child : parent.getComponents())
{
 child.addKeyListener(keyListener);
}