Java/Swing JFC/ComboBox
Содержание
- 1 Add an item after the first item
- 2 Add an item to the end of the list
- 3 Adding and Removing an Item in a JComboBox Component
- 4 A fancy example of JComboBox with a custom renderer and editor
- 5 ArrayListComboBoxModel Demo
- 6 Color ComboBox: ComboBoxEditor Demo
- 7 Color combobox renderer
- 8 Combobox combines a button or editable field and a drop-down list.
- 9 ComboBox Demo
- 10 ComboBox Demo 2
- 11 ComboBox Sample
- 12 ComoboBox loads and saves items automatically from a file
- 13 Create a simple combobox
- 14 Creating a read-only and editable JComboBox Component
- 15 Custom ComboBox with Image
- 16 Determining If the Menu of a JComboBox Component Is Visible
- 17 Determining When the Menu of a JComboBox Component Is Displayed
- 18 Displaying the Menu in a JComboBox Component Using a Keystroke
- 19 Displaying the Menu in a JComboBox Component Using a Keystroke If the Selected Item Is Not Unique
- 20 Editable ComboBox
- 21 Font Chooser ComboBox
- 22 Getting and Setting the Selected Item in a JComboBox Component
- 23 Getting the Items in a JComboBox Component
- 24 If the combobox is editable, the new value can be any value
- 25 Listening for Action Events from a JComboBox Component
- 26 Listening for Changes to the Selected Item in a JComboBox Component
- 27 MultiKey Combo
- 28 PopupCombo Sample
- 29 Remove all items
- 30 Remove first item
- 31 Remove the last item
- 32 Selecting an Item in a JComboBox Component with Multiple Keystrokes
- 33 Selecting Combo Sample
- 34 Select the combobox by choose the nearby label
- 35 Setting the Number of Visible Items in the Menu of a JComboBox Component
- 36 Using drop-down lists
Add an item after the first item
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.insertItemAt("item0.5", 1);
}
}
</source>
Add an item to the end of the list
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.addItem("item3");
}
}
</source>
Adding and Removing an Item in a JComboBox Component
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
// Add an item to the start of the list
cb.insertItemAt("item0", 0);
}
}
</source>
A fancy example of JComboBox with a custom renderer and editor
<source lang="java">
/* Java Swing, 2nd Edition By Marc Loy, Robert Eckstein, Dave Wood, James Elliott, Brian Cole ISBN: 0-596-00408-7 Publisher: O"Reilly
- /
// EditableComboBox.java //A fancy example of JComboBox with a custom renderer and editor used to //display a list of JLabel objects that include both text and icons. // import java.awt.BorderLayout; import java.awt.ruponent; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.util.HashMap; import java.util.Map; import javax.swing.ruboBoxEditor; import javax.swing.Icon; import javax.swing.ImageIcon; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JTextField; import javax.swing.border.BevelBorder; public class EditableComboBox extends JPanel {
private BookEntry books[] = {
new BookEntry("Ant: The Definitive Guide", "covers/ant.gif"),
new BookEntry("Database Programming with JDBC and Java",
"covers/jdbc.gif"),
new BookEntry("Developing Java Beans", "covers/beans.gif"),
new BookEntry("Developing JSP Custom Tag Libraries",
"covers/jsptl.gif"),
new BookEntry("Java 2D Graphics", "covers/java2d.gif"),
new BookEntry("Java and XML", "covers/jxml.gif"),
new BookEntry("Java and XSLT", "covers/jxslt.gif"),
new BookEntry("Java and SOAP", "covers/jsoap.gif"),
new BookEntry("Java and XML Data Binding", "covers/jxmldb.gif"),
new BookEntry("Java Cookbook", "covers/jcook.gif"),
new BookEntry("Java Cryptography", "covers/jcrypto.gif"),
new BookEntry("Java Distributed Computing", "covers/jdist.gif"),
new BookEntry("Java I/O", "covers/javaio.gif"),
new BookEntry("Java in a Nutshell", "covers/javanut.gif"),
new BookEntry("Java Management Extensions", "covers/jmx.gif"),
new BookEntry("Java Message Service", "covers/jms.gif"),
new BookEntry("Java Network Programming", "covers/jnetp.gif"),
new BookEntry("Java Performance Tuning", "covers/jperf.gif"),
new BookEntry("Java RMI", "covers/jrmi.gif"),
new BookEntry("Java Security", "covers/jsec.gif"),
new BookEntry("JavaServer Pages", "covers/jsp.gif"),
new BookEntry("Java Servlet Programming", "covers/servlet.gif"),
new BookEntry("Java Swing", "covers/swing.gif"),
new BookEntry("Java Threads", "covers/jthread.gif"),
new BookEntry("Java Web Services", "covers/jws.gif"),
new BookEntry("Learning Java", "covers/learnj.gif") };
Map bookMap = new HashMap();
public EditableComboBox() {
// Build a mapping from book titles to their entries
for (int i = 0; i < books.length; i++) {
bookMap.put(books[i].getTitle(), books[i]);
}
setLayout(new BorderLayout());
JComboBox bookCombo = new JComboBox(books);
bookCombo.setEditable(true);
bookCombo.setEditor(new ComboBoxEditorExample(bookMap, books[0]));
bookCombo.setMaximumRowCount(4);
bookCombo.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
System.out.println("You chose "
+ ((JComboBox) e.getSource()).getSelectedItem() + "!");
}
});
bookCombo.setActionCommand("Hello");
add(bookCombo, BorderLayout.CENTER);
}
public static void main(String s[]) {
JFrame frame = new JFrame("Combo Box Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setContentPane(new EditableComboBox());
frame.pack();
frame.setVisible(true);
}
} class BookEntry {
private final String title;
private final String imagePath;
private ImageIcon image;
public BookEntry(String title, String imagePath) {
this.title = title;
this.imagePath = imagePath;
}
public String getTitle() {
return title;
}
public ImageIcon getImage() {
if (image == null) {
image = new ImageIcon(imagePath);
}
return image;
}
// Override standard toString method to give a useful result
public String toString() {
return title;
}
} class ComboBoxEditorExample implements ComboBoxEditor {
Map map;
ImagePanel panel;
ImageIcon questionIcon;
public ComboBoxEditorExample(Map m, BookEntry defaultChoice) {
map = m;
panel = new ImagePanel(defaultChoice);
questionIcon = new ImageIcon("question.gif");
}
public void setItem(Object anObject) {
if (anObject != null) {
panel.setText(anObject.toString());
BookEntry entry = (BookEntry) map.get(anObject.toString());
if (entry != null)
panel.setIcon(entry.getImage());
else
panel.setIcon(questionIcon);
}
}
public Component getEditorComponent() {
return panel;
}
public Object getItem() {
return panel.getText();
}
public void selectAll() {
panel.selectAll();
}
public void addActionListener(ActionListener l) {
panel.addActionListener(l);
}
public void removeActionListener(ActionListener l) {
panel.removeActionListener(l);
}
// We create our own inner class to handle setting and
// repainting the image and the text.
class ImagePanel extends JPanel {
JLabel imageIconLabel;
JTextField textField;
public ImagePanel(BookEntry initialEntry) {
setLayout(new BorderLayout());
imageIconLabel = new JLabel(initialEntry.getImage());
imageIconLabel.setBorder(new BevelBorder(BevelBorder.RAISED));
textField = new JTextField(initialEntry.getTitle());
textField.setColumns(45);
textField.setBorder(new BevelBorder(BevelBorder.LOWERED));
add(imageIconLabel, BorderLayout.WEST);
add(textField, BorderLayout.EAST);
}
public void setText(String s) {
textField.setText(s);
}
public String getText() {
return (textField.getText());
}
public void setIcon(Icon i) {
imageIconLabel.setIcon(i);
repaint();
}
public void selectAll() {
textField.selectAll();
}
public void addActionListener(ActionListener l) {
textField.addActionListener(l);
}
public void removeActionListener(ActionListener l) {
textField.removeActionListener(l);
}
}
}
</source>
ArrayListComboBoxModel Demo
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import java.util.ArrayList; import java.util.Collection; import javax.swing.AbstractListModel; import javax.swing.ruboBoxModel; import javax.swing.JComboBox; import javax.swing.JFrame; public class ArrayListComboBoxModel extends AbstractListModel implements
ComboBoxModel {
private Object selectedItem;
private ArrayList anArrayList;
public ArrayListComboBoxModel(ArrayList arrayList) {
anArrayList = arrayList;
}
public Object getSelectedItem() {
return selectedItem;
}
public void setSelectedItem(Object newValue) {
selectedItem = newValue;
}
public int getSize() {
return anArrayList.size();
}
public Object getElementAt(int i) {
return anArrayList.get(i);
}
public static void main(String args[]) {
JFrame frame = new JFrame("ArrayListComboBoxModel");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Collection col = System.getProperties().values();
ArrayList arrayList = new ArrayList(col);
ArrayListComboBoxModel model = new ArrayListComboBoxModel(arrayList);
JComboBox comboBox = new JComboBox(model);
Container contentPane = frame.getContentPane();
contentPane.add(comboBox, BorderLayout.NORTH);
frame.setSize(300, 225);
frame.setVisible(true);
}
}
</source>
Color ComboBox: ComboBoxEditor Demo
<source lang="java">
import java.awt.BorderLayout; import java.awt.Color; import java.awt.ruponent; import java.awt.Container; import java.awt.Dimension; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.ruboBoxEditor; import javax.swing.DefaultListCellRenderer; import javax.swing.JButton; import javax.swing.JColorChooser; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JList; import javax.swing.ListCellRenderer; import javax.swing.event.EventListenerList; public class ColorComboBox {
static class ColorCellRenderer implements ListCellRenderer {
protected DefaultListCellRenderer defaultRenderer = new DefaultListCellRenderer();
// width doesn"t matter as combobox will size
private final static Dimension preferredSize = new Dimension(0, 20);
public Component getListCellRendererComponent(JList list, Object value,
int index, boolean isSelected, boolean cellHasFocus) {
JLabel renderer = (JLabel) defaultRenderer
.getListCellRendererComponent(list, value, index,
isSelected, cellHasFocus);
if (value instanceof Color) {
renderer.setBackground((Color) value);
}
renderer.setPreferredSize(preferredSize);
return renderer;
}
}
public static void main(String args[]) {
Color colors[] = { Color.black, Color.blue, Color.cyan, Color.darkGray,
Color.gray, Color.green, Color.lightGray, Color.magenta,
Color.orange, Color.pink, Color.red, Color.white, Color.yellow };
JFrame frame = new JFrame("Color JComboBox");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container contentPane = frame.getContentPane();
final JComboBox comboBox = new JComboBox(colors);
comboBox.setMaximumRowCount(5);
comboBox.setEditable(true);
comboBox.setRenderer(new ColorCellRenderer());
Color color = (Color) comboBox.getSelectedItem();
ComboBoxEditor editor = new ColorComboBoxEditor(color);
comboBox.setEditor(editor);
contentPane.add(comboBox, BorderLayout.NORTH);
final JLabel label = new JLabel();
label.setOpaque(true);
label.setBackground((Color) comboBox.getSelectedItem());
contentPane.add(label, BorderLayout.CENTER);
ActionListener actionListener = new ActionListener() {
public void actionPerformed(ActionEvent actionEvent) {
Color selectedColor = (Color) comboBox.getSelectedItem();
label.setBackground(selectedColor);
}
};
comboBox.addActionListener(actionListener);
frame.setSize(300, 200);
frame.setVisible(true);
}
} class ColorComboBoxEditor implements ComboBoxEditor {
final protected JButton editor;
transient protected EventListenerList listenerList = new EventListenerList();
public ColorComboBoxEditor(Color initialColor) {
editor = new JButton("");
editor.setBackground(initialColor);
ActionListener actionListener = new ActionListener() {
public void actionPerformed(ActionEvent e) {
Color currentBackground = editor.getBackground();
Color color = JColorChooser.showDialog(editor, "Color Chooser",
currentBackground);
if ((color != null) && (currentBackground != color)) {
editor.setBackground(color);
fireActionEvent(color);
}
}
};
editor.addActionListener(actionListener);
}
public void addActionListener(ActionListener l) {
listenerList.add(ActionListener.class, l);
}
public Component getEditorComponent() {
return editor;
}
public Object getItem() {
return editor.getBackground();
}
public void removeActionListener(ActionListener l) {
listenerList.remove(ActionListener.class, l);
}
public void selectAll() {
// ignore
}
public void setItem(Object newValue) {
if (newValue instanceof Color) {
Color color = (Color) newValue;
editor.setBackground(color);
} else {
// Try to decode
try {
Color color = Color.decode(newValue.toString());
editor.setBackground(color);
} catch (NumberFormatException e) {
// ignore - value unchanged
}
}
}
protected void fireActionEvent(Color color) {
Object listeners[] = listenerList.getListenerList();
for (int i = listeners.length - 2; i >= 0; i -= 2) {
if (listeners[i] == ActionListener.class) {
ActionEvent actionEvent = new ActionEvent(editor,
ActionEvent.ACTION_PERFORMED, color.toString());
((ActionListener) listeners[i + 1])
.actionPerformed(actionEvent);
}
}
}
}
</source>
Color combobox renderer
<source lang="java">
import java.awt.Color; import java.awt.ruponent; import java.awt.Dimension; import java.awt.Graphics; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JList; import javax.swing.JPanel; import javax.swing.ListCellRenderer; import javax.swing.ToolTipManager; import javax.swing.border.rupoundBorder; import javax.swing.border.LineBorder; import javax.swing.border.MatteBorder; public class ColorComboRenderer extends JPanel implements ListCellRenderer {
protected Color m_c = Color.black;
public ColorComboRenderer() {
super();
setBorder(new CompoundBorder(
new MatteBorder(2, 10, 2, 10, Color.white), new LineBorder(
Color.black)));
}
public Component getListCellRendererComponent(JList list, Object obj,
int row, boolean sel, boolean hasFocus) {
if (obj instanceof Color)
m_c = (Color) obj;
return this;
}
public void paint(Graphics g) {
setBackground(m_c);
super.paint(g);
}
public static void main(String[] a) {
JComboBox cbColor = new JComboBox();
int[] values = new int[] { 0, 128, 192, 255 };
for (int r = 0; r < values.length; r++)
for (int g = 0; g < values.length; g++)
for (int b = 0; b < values.length; b++) {
Color c = new Color(values[r], values[g], values[b]);
cbColor.addItem(c);
}
cbColor.setRenderer(new ColorComboRenderer());
JFrame f = new JFrame();
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
f.getContentPane().add(cbColor);
f.pack();
f.setSize(new Dimension(300, 80));
f.show();
}
}
</source>
Combobox combines a button or editable field and a drop-down list.
<source lang="java">
import java.awt.FlowLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import javax.swing.ImageIcon; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JDialog; import javax.swing.JLabel; public class ComboBox extends JDialog implements ActionListener, ItemListener {
final String[] authors = { "A", "B", "C", "D", "E", "F" };
final String[] images = { "a.jpg", "b.jpg", "c.jpg", "d.jpg","e.jpg", "f.jpg" };
JLabel display = new JLabel();
JComboBox combobox = new JComboBox(authors);
JButton button = new JButton("Close");
ImageIcon icon = new ImageIcon(ClassLoader.getSystemResource("a.jpg"));
public ComboBox() {
setLayout(new FlowLayout());
add(display);
combobox.setSelectedIndex(-1);
combobox.addItemListener(this);
add(combobox);
button.addActionListener(this);
add(button);
setSize(300, 300);
setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
setLocationRelativeTo(null);
setVisible(true);
}
public static void main(String[] args) {
new ComboBox();
}
public void actionPerformed(ActionEvent e) {
System.exit(0);
}
public void itemStateChanged(ItemEvent e) {
if (e.getStateChange() == ItemEvent.SELECTED) {
JComboBox combo = (JComboBox) e.getSource();
int index = combo.getSelectedIndex();
display.setIcon(new ImageIcon(ClassLoader.getSystemResource(images[index])));
}
}
}
</source>
ComboBox Demo
<source lang="java">
/* From http://java.sun.ru/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.*; import java.awt.event.*; import javax.swing.*; /*
* ComboBoxDemo.java is a 1.4 application that uses these additional files: * images/Bird.gif * images/Cat.gif * images/Dog.gif * images/Rabbit.gif * images/Pig.gif */
public class ComboBoxDemo extends JPanel
implements ActionListener {
JLabel picture;
public ComboBoxDemo() {
super(new BorderLayout());
String[] petStrings = { "Bird", "Cat", "Dog", "Rabbit", "Pig" };
//Create the combo box, select the item at index 4.
//Indices start at 0, so 4 specifies the pig.
JComboBox petList = new JComboBox(petStrings);
petList.setSelectedIndex(4);
petList.addActionListener(this);
//Set up the picture.
picture = new JLabel();
picture.setFont(picture.getFont().deriveFont(Font.ITALIC));
picture.setHorizontalAlignment(JLabel.CENTER);
updateLabel(petStrings[petList.getSelectedIndex()]);
picture.setBorder(BorderFactory.createEmptyBorder(10,0,0,0));
//The preferred size is hard-coded to be the width of the
//widest image and the height of the tallest image + the border.
//A real program would compute this.
picture.setPreferredSize(new Dimension(177, 122+10));
//Lay out the demo.
add(petList, BorderLayout.PAGE_START);
add(picture, BorderLayout.PAGE_END);
setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
}
/** Listens to the combo box. */
public void actionPerformed(ActionEvent e) {
JComboBox cb = (JComboBox)e.getSource();
String petName = (String)cb.getSelectedItem();
updateLabel(petName);
}
protected void updateLabel(String name) {
ImageIcon icon = createImageIcon("images/" + name + ".gif");
picture.setIcon(icon);
picture.setToolTipText("A drawing of a " + name.toLowerCase());
if (icon != null) {
picture.setText(null);
} else {
picture.setText("Image not found");
}
}
/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
java.net.URL imgURL = ComboBoxDemo.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("ComboBoxDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
JComponent newContentPane = new ComboBoxDemo();
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();
}
});
}
}
</source>
ComboBox Demo 2
<source lang="java">
/* From http://java.sun.ru/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.Color; import java.awt.ruponent; import java.awt.Dimension; import java.awt.GridLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.text.SimpleDateFormat; import java.util.Date; import javax.swing.BorderFactory; import javax.swing.Box; import javax.swing.BoxLayout; import javax.swing.JComboBox; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; /* ComboBoxDemo2.java is a 1.4 application that requires no other files. */ public class ComboBoxDemo2 extends JPanel implements ActionListener {
static JFrame frame;
JLabel result;
String currentPattern;
public ComboBoxDemo2() {
setLayout(new BoxLayout(this, BoxLayout.PAGE_AXIS));
String[] patternExamples = { "dd MMMMM yyyy", "dd.MM.yy", "MM/dd/yy",
"yyyy.MM.dd G "at" hh:mm:ss z", "EEE, MMM d, ""yy", "h:mm a",
"H:mm:ss:SSS", "K:mm a,z", "yyyy.MMMMM.dd GGG hh:mm aaa" };
currentPattern = patternExamples[0];
//Set up the UI for selecting a pattern.
JLabel patternLabel1 = new JLabel("Enter the pattern string or");
JLabel patternLabel2 = new JLabel("select one from the list:");
JComboBox patternList = new JComboBox(patternExamples);
patternList.setEditable(true);
patternList.addActionListener(this);
//Create the UI for displaying result.
JLabel resultLabel = new JLabel("Current Date/Time", JLabel.LEADING); //==
// LEFT
result = new JLabel(" ");
result.setForeground(Color.black);
result.setBorder(BorderFactory.createCompoundBorder(BorderFactory
.createLineBorder(Color.black), BorderFactory
.createEmptyBorder(5, 5, 5, 5)));
//Lay out everything.
JPanel patternPanel = new JPanel();
patternPanel
.setLayout(new BoxLayout(patternPanel, BoxLayout.PAGE_AXIS));
patternPanel.add(patternLabel1);
patternPanel.add(patternLabel2);
patternList.setAlignmentX(Component.LEFT_ALIGNMENT);
patternPanel.add(patternList);
JPanel resultPanel = new JPanel(new GridLayout(0, 1));
resultPanel.add(resultLabel);
resultPanel.add(result);
patternPanel.setAlignmentX(Component.LEFT_ALIGNMENT);
resultPanel.setAlignmentX(Component.LEFT_ALIGNMENT);
add(patternPanel);
add(Box.createRigidArea(new Dimension(0, 10)));
add(resultPanel);
setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
reformat();
} //constructor
public void actionPerformed(ActionEvent e) {
JComboBox cb = (JComboBox) e.getSource();
String newSelection = (String) cb.getSelectedItem();
currentPattern = newSelection;
reformat();
}
/** Formats and displays today"s date. */
public void reformat() {
Date today = new Date();
SimpleDateFormat formatter = new SimpleDateFormat(currentPattern);
try {
String dateString = formatter.format(today);
result.setForeground(Color.black);
result.setText(dateString);
} catch (IllegalArgumentException iae) {
result.setForeground(Color.red);
result.setText("Error: " + iae.getMessage());
}
}
/**
* 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("ComboBoxDemo2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Create and set up the content pane.
JComponent newContentPane = new ComboBoxDemo2();
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();
}
});
}
}
</source>
ComboBox Sample
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import javax.swing.JComboBox; import javax.swing.JFrame; public class ComboBoxSample {
public static void main(String args[]) {
String labels[] = { "A", "B", "C", "D","E", "F", "G", "H","I", "J" };
String title = (args.length == 0 ? "Example JComboBox" : args[0]);
JFrame frame = new JFrame(title);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container contentpane = frame.getContentPane();
JComboBox comboBox1 = new JComboBox(labels);
comboBox1.setMaximumRowCount(5);
contentpane.add(comboBox1, BorderLayout.NORTH);
JComboBox comboBox2 = new JComboBox(labels);
comboBox2.setEditable(true);
contentpane.add(comboBox2, BorderLayout.SOUTH);
frame.setSize(300, 200);
frame.setVisible(true);
}
}
</source>
ComoboBox loads and saves items automatically from a file
<source lang="java">
import java.awt.BorderLayout; import java.awt.Cursor; import java.awt.Dimension; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.awt.event.WindowListener; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.ObjectInput; import java.io.ObjectInputStream; import java.io.ObjectOutput; import java.io.ObjectOutputStream; import java.net.URL; import javax.swing.Box; import javax.swing.BoxLayout; import javax.swing.ruboBoxModel; import javax.swing.JComboBox; import javax.swing.JEditorPane; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTextField; import javax.swing.event.HyperlinkEvent; import javax.swing.event.HyperlinkListener; public class MemComboBoxDemo extends JFrame {
protected MemComboBox urlComboBox = new MemComboBox();
public MemComboBoxDemo() {
super();
setSize(300, 100);
getContentPane().setLayout(new BorderLayout());
JPanel p = new JPanel();
p.setLayout(new BoxLayout(p, BoxLayout.X_AXIS));
p.add(new JLabel("Address"));
urlComboBox.load("addresses.dat");
ComboBoxListener lst = new ComboBoxListener();
urlComboBox.addActionListener(lst);
MemComboAgent agent = new MemComboAgent(urlComboBox);
p.add(urlComboBox);
getContentPane().add(p, BorderLayout.NORTH);
WindowListener wndCloser = new WindowAdapter() {
public void windowClosing(WindowEvent e) {
urlComboBox.save("addresses.dat");
System.exit(0);
}
};
addWindowListener(wndCloser);
setVisible(true);
urlComboBox.grabFocus();
}
class ComboBoxListener implements ActionListener{
public void actionPerformed(ActionEvent evt) {
System.out.println( urlComboBox.getSelectedItem());
}
}
public static void main(String argv[]) {
new MemComboBoxDemo();
}
} class MemComboAgent extends KeyAdapter {
protected JComboBox comboBox;
protected JTextField editor;
public MemComboAgent(JComboBox c) {
comboBox = c;
editor = (JTextField) c.getEditor().getEditorComponent();
editor.addKeyListener(this);
}
public void keyReleased(KeyEvent e) {
char ch = e.getKeyChar();
if (ch == KeyEvent.CHAR_UNDEFINED || Character.isISOControl(ch))
return;
int pos = editor.getCaretPosition();
String str = editor.getText();
if (str.length() == 0)
return;
for (int k = 0; k < comboBox.getItemCount(); k++) {
String item = comboBox.getItemAt(k).toString();
if (item.startsWith(str)) {
editor.setText(item);
editor.setCaretPosition(item.length());
editor.moveCaretPosition(pos);
break;
}
}
}
} class MemComboBox extends JComboBox {
public static final int MAX_MEM_LEN = 30;
public MemComboBox() {
super();
setEditable(true);
}
public void add(String item) {
removeItem(item);
insertItemAt(item, 0);
setSelectedItem(item);
if (getItemCount() > MAX_MEM_LEN)
removeItemAt(getItemCount() - 1);
}
public void load(String fName) {
try {
if (getItemCount() > 0)
removeAllItems();
File f = new File(fName);
if (!f.exists())
return;
FileInputStream fStream = new FileInputStream(f);
ObjectInput stream = new ObjectInputStream(fStream);
Object obj = stream.readObject();
if (obj instanceof ComboBoxModel)
setModel((ComboBoxModel) obj);
stream.close();
fStream.close();
} catch (Exception e) {
System.err.println("Serialization error: " + e.toString());
}
}
public void save(String fName) {
try {
FileOutputStream fStream = new FileOutputStream(fName);
ObjectOutput stream = new ObjectOutputStream(fStream);
stream.writeObject(getModel());
stream.flush();
stream.close();
fStream.close();
} catch (Exception e) {
System.err.println("Serialization error: " + e.toString());
}
}
}
</source>
Create a simple combobox
<source lang="java">
import java.awt.BorderLayout; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.awt.event.WindowListener; import java.util.Vector; import javax.swing.JComboBox; import javax.swing.JFrame; public class ComboBox extends JFrame {
public ComboBox() {
super("ComboBox");
getContentPane().setLayout(new BorderLayout());
Vector cars = new Vector();
cars.addElement("1");
cars.addElement("2");
cars.addElement("3");
getContentPane().add(new JComboBox(cars));
WindowListener wndCloser = new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
};
addWindowListener(wndCloser);
// setResizable(false);
pack();
setVisible(true);
}
public static void main(String argv[]) {
new ComboBox();
}
}
</source>
Creating a read-only and editable JComboBox Component
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
// Create a read-only combobox
String[] items = { "item1", "item2" };
JComboBox readOnlyCB = new JComboBox(items);
// Create an editable combobox
items = new String[] { "item1", "item2" };
JComboBox editableCB = new JComboBox(items);
editableCB.setEditable(true);
}
}
</source>
Custom ComboBox with Image
<source lang="java">
/* From http://java.sun.ru/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.ruponent; 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);
}
}
}
</source>
Determining If the Menu of a JComboBox Component Is Visible
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
// Determine if the menu is visible
boolean isVisible = cb.isPopupVisible();
}
}
</source>
Determining When the Menu of a JComboBox Component Is Displayed
<source lang="java">
import javax.swing.JComboBox; import javax.swing.event.PopupMenuEvent; import javax.swing.event.PopupMenuListener; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.setEditable(true);
MyPopupMenuListener actionListener = new MyPopupMenuListener();
cb.addPopupMenuListener(actionListener);
}
} class MyPopupMenuListener implements PopupMenuListener {
public void popupMenuWillBecomeVisible(PopupMenuEvent evt) {
JComboBox cb = (JComboBox) evt.getSource();
}
public void popupMenuWillBecomeInvisible(PopupMenuEvent evt) {
JComboBox cb = (JComboBox) evt.getSource();
}
public void popupMenuCanceled(PopupMenuEvent evt) {
JComboBox cb = (JComboBox) evt.getSource();
}
}
</source>
Displaying the Menu in a JComboBox Component Using a Keystroke
<source lang="java">
import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "A", "A", "B", "B", "C", "C" };
JComboBox cb = new JComboBox(items);
// Create and register the key listener
cb.addKeyListener(new MyKeyListener());
}
} class MyKeyListener extends KeyAdapter {
public void keyPressed(KeyEvent evt) {
JComboBox cb = (JComboBox) evt.getSource();
// Get pressed character
char ch = evt.getKeyChar();
// If not a printable character, return
if (ch != KeyEvent.CHAR_UNDEFINED) {
cb.showPopup();
}
}
}
</source>
Displaying the Menu in a JComboBox Component Using a Keystroke If the Selected Item Is Not Unique
<source lang="java">
import java.awt.event.KeyAdapter; import java.awt.event.KeyEvent; import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "A", "A", "B", "B", "C" };
JComboBox cb = new JComboBox(items);
// Create and register the key listener
cb.addKeyListener(new MyKeyListener());
}
} class MyKeyListener extends KeyAdapter {
public void keyPressed(KeyEvent evt) {
JComboBox cb = (JComboBox) evt.getSource();
int curIx = cb.getSelectedIndex();
char ch = evt.getKeyChar();
JComboBox.KeySelectionManager ksm = cb.getKeySelectionManager();
if (ksm != null) {
// Determine if another item has the same prefix
int ix = ksm.selectionForKey(ch, cb.getModel());
boolean noMatch = ix < 0;
boolean uniqueItem = ix == curIx;
// Display menu if no matching items or the if the selection is not unique
if (noMatch || !uniqueItem) {
cb.showPopup();
}
}
}
}
</source>
Editable ComboBox
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTextArea; public class EditComboBox {
public static void main(String args[]) {
String labels[] = { "A", "B", "C", "D","E", "F", "G", "H","I", "J" };
JFrame frame = new JFrame("Editable JComboBox");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container contentPane = frame.getContentPane();
final JComboBox comboBox = new JComboBox(labels);
comboBox.setMaximumRowCount(5);
comboBox.setEditable(true);
contentPane.add(comboBox, BorderLayout.NORTH);
final JTextArea textArea = new JTextArea();
JScrollPane scrollPane = new JScrollPane(textArea);
contentPane.add(scrollPane, BorderLayout.CENTER);
ActionListener actionListener = new ActionListener() {
public void actionPerformed(ActionEvent actionEvent) {
textArea.append("Selected: " + comboBox.getSelectedItem());
textArea.append(", Position: " + comboBox.getSelectedIndex());
textArea.append(System.getProperty("line.separator"));
}
};
comboBox.addActionListener(actionListener);
frame.setSize(300, 200);
frame.setVisible(true);
}
}
</source>
Font Chooser ComboBox
<source lang="java">
import java.awt.Font; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; public class FontComboBox extends JFrame implements ActionListener {
JLabel fontLabel = new JLabel(
"The quick brown fox jumps over the lazy dog.");
private JComboBox fontComboBox;
public FontComboBox() {
setTitle("ComboBoxTest");
setSize(300, 200);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
fontComboBox = new JComboBox();
fontComboBox.setEditable(true);
fontComboBox.addItem("Serif");
fontComboBox.addItem("SansSerif");
fontComboBox.addItem("Monospaced");
fontComboBox.addItem("Dialog");
fontComboBox.addItem("DialogInput");
fontComboBox.addActionListener(this);
JPanel p = new JPanel();
p.add(fontComboBox);
getContentPane().add(p, "North");
getContentPane().add(fontLabel, "Center");
}
public void actionPerformed(ActionEvent evt) {
JComboBox source = (JComboBox) evt.getSource();
String item = (String) source.getSelectedItem();
fontLabel.setFont(new Font(item, Font.PLAIN, 12));
}
public static void main(String[] args) {
JFrame frame = new FontComboBox();
frame.show();
}
}
</source>
Getting and Setting the Selected Item in a JComboBox Component
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
// Get current value
Object obj = cb.getSelectedItem();
// Set a new value
cb.setSelectedItem("item2");
obj = cb.getSelectedItem();
// If the new value is not in the list of valid items, the call is ignored
cb.setSelectedItem("item3");
obj = cb.getSelectedItem();
}
}
</source>
Getting the Items in a JComboBox Component
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2", "item3" };
JComboBox cb = new JComboBox(items);
// Get number of items
int num = cb.getItemCount();
// Get items
for (int i = 0; i < num; i++) {
Object item = cb.getItemAt(i);
}
}
}
</source>
If the combobox is editable, the new value can be any value
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
// Create a read-only combobox
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.setEditable(true);
cb.setSelectedItem("item3");
Object obj = cb.getSelectedItem();
}
}
</source>
Listening for Action Events from a JComboBox Component
<source lang="java">
import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.setEditable(true);
// Create and register listener
MyActionListener actionListener = new MyActionListener();
cb.addActionListener(actionListener);
}
} class MyActionListener implements ActionListener {
Object oldItem;
public void actionPerformed(ActionEvent evt) {
JComboBox cb = (JComboBox) evt.getSource();
Object newItem = cb.getSelectedItem();
boolean same = newItem.equals(oldItem);
oldItem = newItem;
if ("comboBoxEdited".equals(evt.getActionCommand())) {
// User has typed in a string; only possible with an editable combobox
} else if ("comboBoxChanged".equals(evt.getActionCommand())) {
// User has selected an item; it may be the same item
}
}
}
</source>
Listening for Changes to the Selected Item in a JComboBox Component
<source lang="java">
import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.setEditable(true);
MyItemListener actionListener = new MyItemListener();
cb.addItemListener(actionListener);
}
} class MyItemListener implements ItemListener {
// This method is called only if a new item has been selected.
public void itemStateChanged(ItemEvent evt) {
JComboBox cb = (JComboBox) evt.getSource();
Object item = evt.getItem();
if (evt.getStateChange() == ItemEvent.SELECTED) {
// Item was just selected
} else if (evt.getStateChange() == ItemEvent.DESELECTED) {
// Item is no longer selected
}
}
}
</source>
MultiKey Combo
<source lang="java">
/* Definitive Guide to Swing for Java 2, Second Edition By John Zukowski ISBN: 1-893115-78-X Publisher: APress
- /
import java.awt.BorderLayout; import java.awt.Container; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import javax.swing.ruboBoxModel; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.Timer; public class MultiKeyCombo {
public static void main(String args[]) {
String labels[] = { "One", "Only", "Once", "Okay", "oneself",
"onlooker", "Onslaught", "Onyx", "onus", "onward" };
JFrame f = new JFrame("Example JList");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComboBox jc = new JComboBox(labels);
MultiKeySelectionManager mk = new MultiKeySelectionManager();
jc.setKeySelectionManager(mk);
// jc.setKeySelectionManager (new JComboBox.KeySelectionManager() {
// public int selectionForKey (char aKey, ComboBoxModel aModel) {
// return -1;
// }
// });
Container c = f.getContentPane();
c.add(jc, BorderLayout.NORTH);
f.setSize(200, 200);
f.setVisible(true);
}
} class MultiKeySelectionManager implements JComboBox.KeySelectionManager {
private StringBuffer currentSearch = new StringBuffer();
private Timer resetTimer;
private final static int RESET_DELAY = 3000;
public MultiKeySelectionManager() {
resetTimer = new Timer(RESET_DELAY, new ActionListener() {
public void actionPerformed(ActionEvent actionEvent) {
currentSearch.setLength(0);
}
});
}
public int selectionForKey(char aKey, ComboBoxModel aModel) {
// Reset if invalid character
if (aKey == KeyEvent.CHAR_UNDEFINED) {
currentSearch.setLength(0);
return -1;
}
// Since search, don"t reset search
resetTimer.stop();
// Convert input to uppercase
char key = Character.toUpperCase(aKey);
// Build up search string
currentSearch.append(key);
// Find selected position within model to starting searching from
Object selectedElement = aModel.getSelectedItem();
int selectedIndex = -1;
if (selectedElement != null) {
for (int i = 0, n = aModel.getSize(); i < n; i++) {
if (aModel.getElementAt(i) == selectedElement) {
selectedIndex = i;
break;
}
}
}
boolean found = false;
String search = currentSearch.toString();
// Search from selected forward, wrap back to beginning if not found
for (int i = 0, n = aModel.getSize(); i < n; i++) {
String element = aModel.getElementAt(selectedIndex).toString()
.toUpperCase();
if (element.startsWith(search)) {
found = true;
break;
}
selectedIndex++;
if (selectedIndex == n) {
selectedIndex = 0; // wrap
}
}
// Restart timer
resetTimer.start();
return (found ? selectedIndex : -1);
}
}
</source>
PopupCombo Sample
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JComponent; import javax.swing.JFrame; import javax.swing.plaf.ruboBoxUI; import javax.swing.plaf.ruponentUI; import javax.swing.plaf.basic.BasicArrowButton; import javax.swing.plaf.basic.BasicComboBoxUI; public class PopupComboSample {
public static void main(String args[]) {
String labels[] = { "A", "B", "C", "D","E", "F", "G", "H","I", "J" };
JFrame frame = new JFrame("Popup JComboBox");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container contentPane = frame.getContentPane();
JComboBox comboBox = new JComboBox(labels);
comboBox.setMaximumRowCount(5);
comboBox.setUI((ComboBoxUI) MyComboBoxUI.createUI(comboBox));
contentPane.add(comboBox, BorderLayout.NORTH);
frame.setSize(300, 200);
frame.setVisible(true);
comboBox.showPopup();
}
static class MyComboBoxUI extends BasicComboBoxUI {
public static ComponentUI createUI(JComponent c) {
return new MyComboBoxUI();
}
protected JButton createArrowButton() {
JButton button = new BasicArrowButton(BasicArrowButton.EAST);
return button;
}
}
}
</source>
Remove all items
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.removeAllItems();
}
}
</source>
Remove first item
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.removeItemAt(0);
}
}
</source>
Remove the last item
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "item1", "item2" };
JComboBox cb = new JComboBox(items);
cb.removeItemAt(cb.getItemCount() - 1);
}
}
</source>
Selecting an Item in a JComboBox Component with Multiple Keystrokes
<source lang="java">
import javax.swing.ruboBoxModel; import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = { "A", "A", "B", "B", "C", "C" };
JComboBox cb = new JComboBox(items);
cb.setKeySelectionManager(new MyKeySelectionManager());
}
} class MyKeySelectionManager implements JComboBox.KeySelectionManager {
long lastKeyTime = 0;
String pattern = "";
public int selectionForKey(char aKey, ComboBoxModel model) {
int selIx = 01;
Object sel = model.getSelectedItem();
if (sel != null) {
for (int i = 0; i < model.getSize(); i++) {
if (sel.equals(model.getElementAt(i))) {
selIx = i;
break;
}
}
}
long curTime = System.currentTimeMillis();
if (curTime - lastKeyTime < 300) {
pattern += ("" + aKey).toLowerCase();
} else {
pattern = ("" + aKey).toLowerCase();
}
lastKeyTime = curTime;
for (int i = selIx + 1; i < model.getSize(); i++) {
String s = model.getElementAt(i).toString().toLowerCase();
if (s.startsWith(pattern)) {
return i;
}
}
for (int i = 0; i < selIx; i++) {
if (model.getElementAt(i) != null) {
String s = model.getElementAt(i).toString().toLowerCase();
if (s.startsWith(pattern)) {
return i;
}
}
}
return -1;
}
}
</source>
Selecting Combo Sample
<source lang="java">
import java.awt.BorderLayout; import java.awt.Container; import java.awt.ItemSelectable; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; import java.io.PrintWriter; import java.io.StringWriter; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JScrollPane; import javax.swing.JTextArea; public class SelectingComboSample {
static private String selectedString(ItemSelectable is) {
Object selected[] = is.getSelectedObjects();
return ((selected.length == 0) ? "null" : (String) selected[0]);
}
public static void main(String args[]) {
String labels[] = { "A", "B", "C", "D","E", "F", "G", "H","J", "I" };
JFrame frame = new JFrame("Selecting JComboBox");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container contentPane = frame.getContentPane();
JComboBox comboBox = new JComboBox(labels);
contentPane.add(comboBox, BorderLayout.SOUTH);
final JTextArea textArea = new JTextArea();
textArea.setEditable(false);
JScrollPane sp = new JScrollPane(textArea);
contentPane.add(sp, BorderLayout.CENTER);
ItemListener itemListener = new ItemListener() {
public void itemStateChanged(ItemEvent itemEvent) {
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
int state = itemEvent.getStateChange();
String stateString = ((state == ItemEvent.SELECTED) ? "Selected": "Deselected");
pw.print("Item: " + itemEvent.getItem());
pw.print(", State: " + stateString);
ItemSelectable is = itemEvent.getItemSelectable();
pw.print(", Selected: " + selectedString(is));
pw.println();
textArea.append(sw.toString());
}
};
comboBox.addItemListener(itemListener);
ActionListener actionListener = new ActionListener() {
public void actionPerformed(ActionEvent actionEvent) {
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
pw.print("Command: " + actionEvent.getActionCommand());
ItemSelectable is = (ItemSelectable) actionEvent.getSource();
pw.print(", Selected: " + selectedString(is));
pw.println();
textArea.append(sw.toString());
}
};
comboBox.addActionListener(actionListener);
frame.setSize(400, 200);
frame.setVisible(true);
}
}
</source>
Select the combobox by choose the nearby label
<source lang="java">
import java.awt.Dimension; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.Box; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; public class LabelForComboBox extends JPanel {
public LabelForComboBox() {
JLabel lbl = new JLabel("Color:");
lbl.setDisplayedMnemonic("c");
add(lbl);
add(Box.createHorizontalStrut(20));
JComboBox cbColor = new JComboBox();
cbColor.addItem("red");
cbColor.addItem("blue");
lbl.setLabelFor(cbColor);
add(cbColor);
}
public static void main(String[] a) {
JFrame f = new JFrame();
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
f.getContentPane().add(new LabelForComboBox());
f.pack();
f.setSize(new Dimension(300, 200));
f.show();
}
}
</source>
Setting the Number of Visible Items in the Menu of a JComboBox Component
<source lang="java">
import javax.swing.JComboBox; public class Main {
public static void main(String[] argv) throws Exception {
String[] items = new String[50];
for (int i = 0; i < items.length; i++) {
items[i] = "" + Math.random();
}
JComboBox cb = new JComboBox(items);
// Retrieve the current max visible rows
int maxVisibleRows = cb.getMaximumRowCount();
// Change the current max visible rows
maxVisibleRows = 20;
cb.setMaximumRowCount(maxVisibleRows);
}
}
</source>
Using drop-down lists
<source lang="java">
// : c14:ComboBoxes.java // Using drop-down lists. // <applet code=ComboBoxes width=200 height=125></applet> // From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002 // www.BruceEckel.ru. See copyright notice in CopyRight.txt. import java.awt.Container; import java.awt.FlowLayout; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import javax.swing.JApplet; import javax.swing.JButton; import javax.swing.JComboBox; import javax.swing.JFrame; import javax.swing.JTextField; public class ComboBoxes extends JApplet {
private String[] description = { "Ebullient", "Obtuse", "Recalcitrant",
"Brilliant", "Somnescent", "Timorous", "Florid", "Putrescent" };
private JTextField t = new JTextField(15);
private JComboBox c = new JComboBox();
private JButton b = new JButton("Add items");
private int count = 0;
public void init() {
for (int i = 0; i < 4; i++)
c.addItem(description[count++]);
t.setEditable(false);
b.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (count < description.length)
c.addItem(description[count++]);
}
});
c.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
t.setText("index: " + c.getSelectedIndex() + " "
+ ((JComboBox) e.getSource()).getSelectedItem());
}
});
Container cp = getContentPane();
cp.setLayout(new FlowLayout());
cp.add(t);
cp.add(c);
cp.add(b);
}
public static void main(String[] args) {
run(new ComboBoxes(), 200, 125);
}
public static void run(JApplet applet, int width, int height) {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(applet);
frame.setSize(width, height);
applet.init();
applet.start();
frame.setVisible(true);
}
} ///:~
</source>
