/*
 * 1.1 code.
 */

import java.applet.Applet;
import java.awt.*;
import java.awt.event.ContainerEvent;
import java.awt.event.ContainerListener;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Vector;

public class ContainerEventDemo extends Applet 
			        implements ContainerListener,
				           ActionListener {
    TextArea display;
    Panel buttonPanel;
    Button addButton, removeButton, clearButton;
    Vector buttonList;
    static final String ADD = "add";
    static final String REMOVE = "remove";
    static final String CLEAR = "clear";
    String newline;

    public void init() {
	newline = System.getProperty("line.separator");

	//Initialize an empty list of buttons.
	buttonList = new Vector(10, 10);

	//Create all the components.
	addButton = new Button("Add a button");
	addButton.setActionCommand(ADD);
	addButton.addActionListener(this);

	removeButton = new Button("Remove a button");
	removeButton.setActionCommand(REMOVE);
	removeButton.addActionListener(this);

	buttonPanel = new Panel();
	buttonPanel.addContainerListener(this);

	display = new TextArea(5, 20);
	display.setEditable(false);

	clearButton = new Button("Clear text area");
	clearButton.setActionCommand(CLEAR);
	clearButton.addActionListener(this);

	//Lay out the components.
	GridBagLayout gridbag = new GridBagLayout();
	GridBagConstraints c = new GridBagConstraints();
	setLayout(gridbag);
	c.fill = GridBagConstraints.BOTH; //Fill entire cell.

        c.weighty = 1.0;  //Button area and message area have equal height.
	c.gridwidth = GridBagConstraints.REMAINDER; //end of row
	gridbag.setConstraints(display, c);
	add(display);

        c.weighty = 0.0;  
	gridbag.setConstraints(clearButton, c);
	add(clearButton);

        c.weightx = 1.0;  //Add/remove buttons have equal width.
	c.gridwidth = 1;  //NOT end of row
	gridbag.setConstraints(addButton, c);
	add(addButton);

	c.gridwidth = GridBagConstraints.REMAINDER; //end of row
	gridbag.setConstraints(removeButton, c);
	add(removeButton);

        c.weighty = 1.0;  //Button area and message area have equal height.
	gridbag.setConstraints(buttonPanel, c);
	add(buttonPanel);
    }

    public void componentAdded(ContainerEvent e) {
	displayMessage(" added to ", e);
    }

    public void componentRemoved(ContainerEvent e) {
	displayMessage(" removed from ", e);
    }

    void displayMessage(String action, ContainerEvent e) {
	display.append(((Button)e.getChild()).getLabel()
		       + " was"
		       + action
		       + e.getContainer().getClass().getName()
		       + newline);
    }

    /*
     * This could have been implemented as two or three
     * classes or objects, for clarity.
     */
    public void actionPerformed(ActionEvent e) {
	String command = e.getActionCommand();

	if (command == ADD) {
	    Button newButton = new Button("Button #"
	                                  + (buttonList.size() + 1));
	    buttonList.addElement(newButton);
	    buttonPanel.add(newButton);
	    buttonPanel.validate(); //Make the button show up.
	} else if (command == REMOVE) {
	    int lastIndex = buttonList.size() - 1;
	    try {
	        Button nixedButton = (Button)buttonList.elementAt(lastIndex);
	        buttonPanel.remove(nixedButton);
		buttonList.removeElementAt(lastIndex);
	        buttonPanel.validate(); //Make the button disappear.
	    } catch (ArrayIndexOutOfBoundsException exc) {
	    }
	} else if (command == CLEAR) {
	    display.setText("");
	}
    }
}