import java.awt.*;
import java.awt.event.*;

public class EscapeDialog extends Dialog implements ContainerListener, KeyListener
{

     public EscapeDialog(Frame frame, String title, boolean modal)
     {
          super(frame, title, modal);
          addKeyAndContainerListenerRecursively(this);
     }


//The following function is recursive and is intended for internal use only. It is private to prevent anyone calling it from other classes
//The function takes a Component as an argument and adds this Dialog as a KeyListener to it.
//Besides it checks if the component is actually a Container and if it is, there  are 2 additional things to be done to this Container :
// 1 - add this Dialog as a ContainerListener to the Container
// 2 - call this function recursively for every child of the Container.

     private void addKeyAndContainerListenerRecursively(Component c)
     {
//To be on the safe side, try to remove KeyListener first just in case it has been added before.
//If not, it won't do any harm
          c.removeKeyListener(this);
//Add KeyListener to the Component passed as an argument
          c.addKeyListener(this);

          if(c instanceof Container){

//Component c is a Container. The following cast is safe.
               Container cont = (Container)c;

//To be on the safe side, try to remove ContainerListener first just in case it has been added before.
//If not, it won't do any harm
               cont.removeContainerListener(this);
//Add ContainerListener to the Container.
               cont.addContainerListener(this);

//Get the Container's array of children Components.
               Component[] children = cont.getComponents();

//For every child repeat the above operation.
               for(int i = 0; i < children.length; i++){
                    addKeyAndContainerListenerRecursively(children[i]);
               }
          }
     }


//The following function is the same as the function above with the exception that it does exactly the opposite - removes this Dialog
//from the listener lists of Components.

    private void removeKeyAndContainerListenerRecursively(Component c)
    {
          c.removeKeyListener(this);

          if(c instanceof Container){

               Container cont = (Container)c;

               cont.removeContainerListener(this);

               Component[] children = cont.getComponents();

               for(int i = 0; i < children.length; i++){
                    removeKeyAndContainerListenerRecursively(children[i]);
               }
          }
     }


//ContainerListener interface
/**********************************************************/

//This function is called whenever a Component or a Container is added to another Container belonging to this Dialog
     public void componentAdded(ContainerEvent e)
     {
          addKeyAndContainerListenerRecursively(e.getChild());
     }

//This function is called whenever a Component or a Container is removed from another Container belonging to this Dialog
     public void componentRemoved(ContainerEvent e)
     {
          removeKeyAndContainerListenerRecursively(e.getChild());
     }

/**********************************************************/


//KeyListener interface
/**********************************************************/
//This function is called whenever a Component belonging to this Dialog (or the Dialog itself) gets the KEY_PRESSED event
     public void keyPressed(KeyEvent e)
     {
          int code = e.getKeyCode();
          if(code == KeyEvent.VK_ESCAPE){
//Key pressed is the ESCAPE key. Hide this Dialog.
               setVisible(false);
          }
          else if(code == KeyEvent.VK_ENTER){
//Key pressed is the ENTER key. Redefine performEnterAction() in subclasses to respond to depressing the ENTER key.
               performEnterAction(e);
          }

//Insert code to process other keys here
     }

//We need the following 2 functions to complete imlementation of KeyListener
     public void keyReleased(KeyEvent e)
     {
     }

     public void keyTyped(KeyEvent e)
     {
     }

/************************************************************/

     void performEnterAction(KeyEvent e)
     {
//Default response to ENTER key pressed goes here
//Redefine this function in subclasses to respond to ENTER key differently
     }

}