comboboxdemo.java

Java与面向对象程序设计实验教学讲义.复数类的实现,复数类的复杂运算,身份证号码的分析,图形界面设计

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

public class ComboBoxDemo extends JPanel {
    JLabel picture;

    public ComboBoxDemo() {
        String[] petStrings = { "Bird", "Cat", "Dog", "Rabbit", "Pig" };

        // Create the combo box, select the pig
        JComboBox petList = new JComboBox(petStrings);
        petList.setSelectedIndex(4);
        petList.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                JComboBox cb = (JComboBox)e.getSource();
                String petName = (String)cb.getSelectedItem();
                picture.setIcon(new ImageIcon("./build/classes/" + petName + ".gif"));
            }
        });

        // Set up the picture
        picture = new JLabel(new ImageIcon("./build/classes/" +
                                   petStrings[petList.getSelectedIndex()] +
                                   ".gif"));
        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));

        // Layout the demo
        setLayout(new BorderLayout());
        add(petList, BorderLayout.NORTH);
        add(picture, BorderLayout.SOUTH);
        setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
    }

    public static void main(String s[]) {
        JFrame frame = new JFrame("ComboBoxDemo");

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