Thứ Ba, 26 tháng 3, 2013

Java JComboBox class example

Java Swing Tutorial Explaining the JComboBox Component. JComboBox is like a drop down box — you can click a drop-down arrow and select an option from a list. It generates ItemEvent. For example, when the component has focus, pressing a key that corresponds to the first character in some entry’s name selects that entry. A vertical scrollbar is used for longer lists.

JComboBox Source Code

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class JComboBoxDemo extends JPanel {

JLabel jlbPicture;
public JComboBoxDemo() {
String[] comboTypes = { "Numbers", "Alphabets", "Symbols" };
// Create the combo box, and set 2nd item as Default
JComboBox comboTypesList = new JComboBox(comboTypes);
comboTypesList.setSelectedIndex(2);
comboTypesList.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {
JComboBox jcmbType = (JComboBox) e.getSource();
String cmbType = (String) jcmbType.getSelectedItem();
jlbPicture.setIcon(new ImageIcon(""
+ cmbType.trim().toLowerCase() + ".jpg"));
}
});
// Set up the picture
jlbPicture = new JLabel(new ImageIcon(""
+ comboTypes[comboTypesList.getSelectedIndex()] + ".jpg"));
jlbPicture.setBorder(BorderFactory.createEmptyBorder(10, 0, 0, 0));
jlbPicture.setPreferredSize(new Dimension(177, 122 + 10));
// Layout the demo
setLayout(new BorderLayout());
add(comboTypesList, BorderLayout.NORTH);
add(jlbPicture, BorderLayout.SOUTH);
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
}
public static void main(String s[]) {
JFrame frame = new JFrame("JComboBox Usage Demo");
frame.addWindowListener(new WindowAdapter() {

public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
frame.setContentPane(new JComboBoxDemo());
frame.pack();
frame.setVisible(true);
}
}

 Output

Download JComboBox Source Code

Another Example: JComboBox Source Code

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import java.util.*;
import java.text.*;

public class DateComboBoxDemo extends JPanel {

static JFrame frame;
JLabel jlbResult;
String datePattern_Current;
public DateComboBoxDemo() {
String[] datePatterns = { "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" };
datePattern_Current = datePatterns[0];
// Set up the UI for selecting a pattern.
JLabel jlbHeading = new JLabel(
"Enter Date pattern /Select from list:");
JComboBox patternList = new JComboBox(datePatterns);
patternList.setEditable(true);
patternList.setAlignmentX(Component.LEFT_ALIGNMENT);
patternList.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e) {
JComboBox jcmbDates = (JComboBox) e.getSource();
String seletedDate = (String) jcmbDates.getSelectedItem();
datePattern_Current = seletedDate;
showDateinLabel();
}
});
// Create the UI for displaying result
JLabel jlbResultHeading = new JLabel("Current Date/Time",
JLabel.LEFT);
jlbResult = new JLabel(" ");
jlbResult.setForeground(Color.black);
jlbResult.setBorder(BorderFactory.createCompoundBorder(
BorderFactory.createLineBorder(Color.black), BorderFactory
.createEmptyBorder(5, 5, 5, 5)));
// Lay out everything
JPanel jpnDate = new JPanel();
jpnDate.setLayout(new BoxLayout(jpnDate, BoxLayout.Y_AXIS));
jpnDate.add(jlbHeading);
jpnDate.add(patternList);
JPanel jpnResults = new JPanel();
jpnResults.setLayout(new GridLayout(0, 1));
jpnResults.add(jlbResultHeading);
jpnResults.add(jlbResult);
setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
jpnDate.setAlignmentX(Component.LEFT_ALIGNMENT);
jpnResults.setAlignmentX(Component.LEFT_ALIGNMENT);
add(jpnDate);
add(Box.createRigidArea(new Dimension(0, 10)));
add(jpnResults);
setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
showDateinLabel();
} // constructor
/** Formats and displays today's date. */
public void showDateinLabel() {
Date today = new Date();
SimpleDateFormat formatter = new SimpleDateFormat(
datePattern_Current);
try {
String dateString = formatter.format(today);
jlbResult.setForeground(Color.black);
jlbResult.setText(dateString);
} catch (IllegalArgumentException e) {
jlbResult.setForeground(Color.red);
jlbResult.setText("Error: " + e.getMessage());
}
}
public static void main(String s[]) {
frame = new JFrame("JComboBox Usage Demo");
frame.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
frame.setContentPane(new DateComboBoxDemo());
frame.pack();
frame.setVisible(true);
}
}

Output

Download JComboBox Source Code

Java JComboBox Hierarchy

javax.swing
Class JComboBox 
java.lang.Object
java.awt.Component
java.awt.Container
javax.swing.JComponent
javax.swing.JComboBox
All Implemented Interfaces: 
Accessible, ActionListener, EventListener, ImageObserver, ItemSelectable, ListDataListener, MenuContainer, Serializable

JComboBox Constructor

JComboBox()
Creates a JComboBox with a default data model.

JComboBox(ComboBoxModel aModel)
Creates a JComboBox that takes it’s items from an existing ComboBoxModel.

JComboBox(Object[] items)
Creates a JComboBox that contains the elements in the specified array.

JComboBox(Vector items)
Creates a JComboBox that contains the elements in the specified Vector.

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