Java tutorial
/* From http://java.sun.com/docs/books/tutorial/index.html */ /* * Copyright (c) 2006 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: * * -Redistribution of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * -Redistribution 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, Inc. or the names of contributors may * be used to endorse or promote products derived from this software without * specific prior written permission. * * This software is provided "AS IS," without a warranty of any kind. ALL * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN") * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. * * You acknowledge that this software is not designed, licensed or intended * for use in the design, construction, operation or maintenance of any * nuclear facility. */ /* * FocusEventDemo.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.Insets; import java.awt.event.FocusEvent; import java.awt.event.FocusListener; import java.util.Vector; import javax.swing.BorderFactory; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTextArea; import javax.swing.JTextField; public class FocusEventDemo extends JPanel implements FocusListener { final static String newline = "\n"; JTextArea display; public FocusEventDemo() { super(new GridBagLayout()); GridBagLayout gridbag = (GridBagLayout) getLayout(); GridBagConstraints c = new GridBagConstraints(); c.fill = GridBagConstraints.HORIZONTAL; c.weightx = 1.0; //Make column as wide as possible. JTextField textField = new JTextField("A TextField"); textField.setMargin(new Insets(0, 2, 0, 2)); textField.addFocusListener(this); gridbag.setConstraints(textField, c); add(textField); c.weightx = 0.1; //Widen every other column a bit, when possible. c.fill = GridBagConstraints.NONE; JLabel label = new JLabel("A Label"); label.setBorder(BorderFactory.createEmptyBorder(0, 5, 0, 5)); label.addFocusListener(this); gridbag.setConstraints(label, c); add(label); String comboPrefix = "ComboBox Item #"; final int numItems = 15; Vector vector = new Vector(numItems); for (int i = 0; i < numItems; i++) { vector.addElement(comboPrefix + i); } JComboBox comboBox = new JComboBox(vector); comboBox.addFocusListener(this); gridbag.setConstraints(comboBox, c); add(comboBox); c.gridwidth = GridBagConstraints.REMAINDER; JButton button = new JButton("A Button"); button.addFocusListener(this); gridbag.setConstraints(button, c); add(button); c.weightx = 0.0; c.weighty = 0.1; c.fill = GridBagConstraints.BOTH; String listPrefix = "List Item #"; Vector listVector = new Vector(numItems); for (int i = 0; i < numItems; i++) { listVector.addElement(listPrefix + i); } JList list = new JList(listVector); list.setSelectedIndex(1); //It's easier to see the focus change //if an item is selected. list.addFocusListener(this); JScrollPane listScrollPane = new JScrollPane(list); //We want to prevent the list's scroll bars //from getting the focus - even with the keyboard. //Note that in general we prefer setRequestFocusable //over setFocusable for reasons of accessibility, //but this is to work around bug #4866958. listScrollPane.getVerticalScrollBar().setFocusable(false); listScrollPane.getHorizontalScrollBar().setFocusable(false); gridbag.setConstraints(listScrollPane, c); add(listScrollPane); c.weighty = 1.0; //Make this row as tall as possible. c.gridheight = GridBagConstraints.REMAINDER; //Set up the area that reports focus-gained and focus-lost events. display = new JTextArea(); display.setEditable(false); //The method setRequestFocusEnabled prevents a //component from being clickable, but it can still //get the focus through the keyboard - this ensures //user accessibility. display.setRequestFocusEnabled(false); display.addFocusListener(this); JScrollPane displayScrollPane = new JScrollPane(display); //Work around for bug #4866958. displayScrollPane.getHorizontalScrollBar().setFocusable(false); displayScrollPane.getVerticalScrollBar().setFocusable(false); gridbag.setConstraints(displayScrollPane, c); add(displayScrollPane); setPreferredSize(new Dimension(450, 450)); setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20)); } public void focusGained(FocusEvent e) { displayMessage("Focus gained", e); } public void focusLost(FocusEvent e) { displayMessage("Focus lost", e); } void displayMessage(String prefix, FocusEvent e) { display.append(prefix + (e.isTemporary() ? " (temporary):" : ":") + e.getComponent().getClass().getName() + "; Opposite component: " + (e.getOppositeComponent() != null ? e.getOppositeComponent().getClass().getName() : "null") + newline); display.setCaretPosition(display.getDocument().getLength()); } /** * 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("FocusEventDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane. JComponent newContentPane = new FocusEventDemo(); 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(); } }); } }