Java tutorial
/* * Copyright (c) 1995 - 2008 Sun Microsystems, Inc. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * - Neither the name of Sun Microsystems nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* * ContainerEventDemo.java 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<JButton> 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<JButton>(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 = 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() { // 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(); } }); } }