ComboBoxDemo.java

/*
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 * modification, are permitted provided that the following conditions
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 *
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 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions 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 Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package javademo.swing.ComboBox.ComboBoxDemo;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

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.JPanel;

/*
 * ComboBoxDemo.java uses these additional files:
 *   images/Bird.gif
 *   images/Cat.gif
 *   images/Dog.gif
 *   images/Rabbit.gif
 *   images/Pig.gif
 */
@SuppressWarnings("serial")
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()
    {
        // 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();
            }
        });
    }
}