Java JComboBox class example

byVi-et Spaces 0 Nhận xét

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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