package components; import java.awt.*; import java.awt.event.*; import javax.swing.*; /* * CustomComboBoxDemo.java 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() { //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); } } }
