/*
* Swing version
*/
import javax.swing.*;
import java.awt.Dimension;
import java.awt.GridBagLayout;
import java.awt.GridBagConstraints;
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 JApplet
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 void init() {
//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();
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);
//Lay out the components.
GridBagLayout gridbag = new GridBagLayout();
GridBagConstraints c = new GridBagConstraints();
JPanel contentPane = new JPanel();
contentPane.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(scrollPane, c);
contentPane.add(scrollPane);
c.weighty = 0.0;
gridbag.setConstraints(clearButton, c);
contentPane.add(clearButton);
c.weightx = 1.0; //Add/remove buttons have equal width.
c.gridwidth = 1; //NOT end of row
gridbag.setConstraints(addButton, c);
contentPane.add(addButton);
c.gridwidth = GridBagConstraints.REMAINDER; //end of row
gridbag.setConstraints(removeButton, c);
contentPane.add(removeButton);
c.weighty = 1.0; //Button area and message area have equal height.
gridbag.setConstraints(buttonPanel, c);
contentPane.add(buttonPanel);
setContentPane(contentPane);
}
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);
}
/*
* 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) {
JButton newButton = new JButton("JButton #"
+ (buttonList.size() + 1));
buttonList.addElement(newButton);
buttonPanel.add(newButton);
buttonPanel.revalidate(); //Make the button show up.
} else if (command == REMOVE) {
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 (command == CLEAR) {
display.setText("");
}
}
}
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