public class CustomComboBoxDemo extends JPanel {
ImageIcon[] images;
String[] petStrings = {"Bird", "Cat", "Dog", "Rabbit", "Pig"};
public CustomComboBoxDemo() {
super(new BorderLayout());
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]);
}
}
JComboBox petList = new JComboBox(intArray);
ComboBoxRenderer renderer= new ComboBoxRenderer();
renderer.setPreferredSize(new Dimension(200, 130));
petList.setRenderer(renderer);
petList.setMaximumRowCount(3);
add(petList, BorderLayout.PAGE_START);
setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
}
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;
}
}
private static void createAndShowGUI() {
JFrame frame = new JFrame("CustomComboBoxDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new CustomComboBoxDemo();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
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);
}
public Component getListCellRendererComponent(
JList list,
Object value,
int index,
boolean isSelected,
boolean cellHasFocus) {
int selectedIndex = ((Integer)value).intValue();
if (isSelected) {
setBackground(list.getSelectionBackground());
setForeground(list.getSelectionForeground());
} else {
setBackground(list.getBackground());
setForeground(list.getForeground());
}
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;
}
protected void setUhOhText(String uhOhText, Font normalFont) {
if (uhOhFont == null) { //lazily create this font
uhOhFont = normalFont.deriveFont(Font.ITALIC);
}
setFont(uhOhFont);
setText(uhOhText);
}
}
}
这个程序有些看不懂，麻烦哪位给我把每步注明一下，特别是
class ComboBoxRenderer 和 protected void setUhOhText(String uhOhText, Font normalFont)
里面的内容。最好讲详细点啊。