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. */ import java.awt.BorderLayout; import java.awt.Component; import java.awt.Dimension; import java.awt.Font; import javax.swing.BorderFactory; import javax.swing.ImageIcon; 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.ListCellRenderer; /* * CustomComboBoxDemo.java is a 1.4 application that uses the following files: * images/Bird.gif * images/Cat.gif * images/Dog.gif * images/Rabbit.gif * images/Pig.gif */ public class CustomComboBoxDemo extends JPanel { ImageIcon[] images; String[] petStrings = { "Bird", "Cat", "Dog", "Rabbit", "Pig" }; /* * Despite its use of EmptyBorder, this panel makes a fine content * pane because the empty border just increases the panel's size * and is "painted" on top of the panel's normal background. In * other words, the JPanel fills its entire background if it's * opaque (which it is by default); adding a border doesn't change * that. */ public CustomComboBoxDemo() { super(new BorderLayout()); //Load the pet images and create an array of indexes. images = new ImageIcon[petStrings.length]; Integer[] intArray = new Integer[petStrings.length]; for (int i = 0; i < petStrings.length; i++) { intArray[i] = new Integer(i); images[i] = createImageIcon("images/" + petStrings[i] + ".gif"); if (images[i] != null) { images[i].setDescription(petStrings[i]); } } //Create the combo box. JComboBox petList = new JComboBox(intArray); ComboBoxRenderer renderer = new ComboBoxRenderer(); renderer.setPreferredSize(new Dimension(200, 130)); petList.setRenderer(renderer); petList.setMaximumRowCount(3); //Lay out the demo. add(petList, BorderLayout.PAGE_START); setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20)); } /** Returns an ImageIcon, or null if the path was invalid. */ protected static ImageIcon createImageIcon(String path) { java.net.URL imgURL = CustomComboBoxDemo.class.getResource(path); if (imgURL != null) { return new ImageIcon(imgURL); } else { System.err.println("Couldn't find file: " + path); return null; } } /** * 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("CustomComboBoxDemo"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane. JComponent newContentPane = new CustomComboBoxDemo(); 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(); } }); } class ComboBoxRenderer extends JLabel implements ListCellRenderer { private Font uhOhFont; public ComboBoxRenderer() { setOpaque(true); setHorizontalAlignment(CENTER); setVerticalAlignment(CENTER); } /* * This method finds the image and text corresponding * to the selected value and returns the label, set up * to display the text and image. */ public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) { //Get the selected index. (The index param isn't //always valid, so just use the value.) int selectedIndex = ((Integer) value).intValue(); if (isSelected) { setBackground(list.getSelectionBackground()); setForeground(list.getSelectionForeground()); } else { setBackground(list.getBackground()); setForeground(list.getForeground()); } //Set the icon and text. If icon was null, say so. ImageIcon icon = images[selectedIndex]; String pet = petStrings[selectedIndex]; setIcon(icon); if (icon != null) { setText(pet); setFont(list.getFont()); } else { setUhOhText(pet + " (no image available)", list.getFont()); } return this; } //Set the font and text when no image was found. protected void setUhOhText(String uhOhText, Font normalFont) { if (uhOhFont == null) { //lazily create this font uhOhFont = normalFont.deriveFont(Font.ITALIC); } setFont(uhOhFont); setText(uhOhText); } } }