/* From http://java.sun.com/docs/books/tutorial/index.html */
/*
 * ContainerEventDemo.java is a 1.4 example that requires no other files.
 */

import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ContainerEvent;
import java.awt.event.ContainerListener;
import java.util.Vector;

import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class ContainerEventDemo extends JPanel implements ContainerListener,
    ActionListener {
  JTextArea display;

  JPanel buttonPanel;

  JButton addButton, removeButton, clearButton;

  Vector buttonList;

  static final String ADD = "add";

  static final String REMOVE = "remove";

  static final String CLEAR = "clear";

  static final String newline = "\n";

  public ContainerEventDemo() {
    super(new GridBagLayout());
    GridBagLayout gridbag = (GridBagLayout) getLayout();
    GridBagConstraints c = new GridBagConstraints();

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

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

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

    buttonPanel = new JPanel(new GridLayout(1, 1));
    buttonPanel.setPreferredSize(new Dimension(200, 75));
    buttonPanel.addContainerListener(this);

    display = new JTextArea();
    display.setEditable(false);
    JScrollPane scrollPane = new JScrollPane(display);
    scrollPane.setPreferredSize(new Dimension(200, 75));

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

    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(scrollPane, c);
    add(scrollPane);

    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);

    setPreferredSize(new Dimension(400, 400));
    setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
  }

  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(((JButton) e.getChild()).getText() + " was" + action
        + e.getContainer().getClass().getName() + newline);
    display.setCaretPosition(display.getDocument().getLength());
  }

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

    if (ADD.equals(command)) {
      JButton newButton = new JButton("JButton #"
          + (buttonList.size() + 1));
      buttonList.addElement(newButton);
      buttonPanel.add(newButton);
      buttonPanel.revalidate(); //Make the button show up.

    } else if (REMOVE.equals(command)) {
      int lastIndex = buttonList.size() - 1;
      try {
        JButton nixedButton = (JButton) buttonList.elementAt(lastIndex);
        buttonPanel.remove(nixedButton);
        buttonList.removeElementAt(lastIndex);
        buttonPanel.revalidate(); //Make the button disappear.
        buttonPanel.repaint(); //Make the button disappear.
      } catch (ArrayIndexOutOfBoundsException exc) {
      }
    } else if (CLEAR.equals(command)) {
      display.setText("");
    }
  }

  /**
   * Create the GUI and show it. For thread safety, this method should be
   * invoked from the event-dispatching thread.
   */
  private static void createAndShowGUI() {
    //Make sure we have nice window decorations.
    JFrame.setDefaultLookAndFeelDecorated(true);

    //Create and set up the window.
    JFrame frame = new JFrame("ContainerEventDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create and set up the content pane.
    JComponent newContentPane = new ContainerEventDemo();
    newContentPane.setOpaque(true); //content panes must be opaque
    frame.setContentPane(newContentPane);

    //Display the window.
    frame.pack();
    frame.setVisible(true);
  }

  public static void main(String[] args) {
    //Schedule a job for the event-dispatching thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
      public void run() {
        createAndShowGUI();
      }
    });
  }
}