checkboxdemo.java

简单复选框演示程序

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

public class CheckBoxDemo extends JPanel
                          implements ItemListener {
    JCheckBox chinButton;
    JCheckBox glassesButton;
    JCheckBox hairButton;
    JCheckBox teethButton;

    StringBuffer choices;
    JLabel pictureLabel;

    public CheckBoxDemo() {
        super(new BorderLayout());

        //Create the check boxes.  创建复选框
        chinButton = new JCheckBox("Chin");   //创建chin复选框
        chinButton.setMnemonic(KeyEvent.VK_C);
        chinButton.setSelected(true);

        glassesButton = new JCheckBox("Glasses");  //创建glasses复选框
        glassesButton.setMnemonic(KeyEvent.VK_G);
        glassesButton.setSelected(true);

        hairButton = new JCheckBox("Hair");  //创建hair复选框
        hairButton.setMnemonic(KeyEvent.VK_H);
        hairButton.setSelected(true);

        teethButton = new JCheckBox("Teeth");  //创建teeth复选框
        teethButton.setMnemonic(KeyEvent.VK_T);
        teethButton.setSelected(true);

        //Register a listener for the check boxes.  注册监听器对象
        chinButton.addItemListener(this);
        glassesButton.addItemListener(this);
        hairButton.addItemListener(this);
        teethButton.addItemListener(this);

        //Indicates what's on the geek.
        choices = new StringBuffer("cght");

        //Set up the picture label
        pictureLabel = new JLabel();
        pictureLabel.setFont(pictureLabel.getFont().deriveFont(Font.ITALIC));
        updatePicture();    //显示图形

        //Put the check boxes in a column in a panel   添加复选框到面板中
        JPanel checkPanel = new JPanel(new GridLayout(0, 1));
        checkPanel.add(chinButton);
        checkPanel.add(glassesButton);
        checkPanel.add(hairButton);
        checkPanel.add(teethButton);

        add(checkPanel, BorderLayout.LINE_START);
        add(pictureLabel, BorderLayout.CENTER);
        setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
    }

    /** Listens to the check boxes. */
    public void itemStateChanged(ItemEvent e) {
        int index = 0;
        char c = '-';
        Object source = e.getItemSelectable();

        if (source == chinButton) {
            index = 0;
            c = 'c';
        } else if (source == glassesButton) {
            index = 1;
            c = 'g';
        } else if (source == hairButton) {
            index = 2;
            c = 'h';
        } else if (source == teethButton) {
            index = 3;
            c = 't';
        }

        //Now that we know which button was pushed, find out
        //whether it was selected or deselected. 如果是复选框没有被打勾，则c为'_'
        if (e.getStateChange() == ItemEvent.DESELECTED) {
            c = '-';
        }

        //Apply the change to the string.
        choices.setCharAt(index, c);

        updatePicture();
    }

    protected void updatePicture() {
        //Get the icon corresponding to the image.
        ImageIcon icon = createImageIcon(
                                    "images/geek/geek-"
                                    + choices.toString()
                                    + ".gif");
        pictureLabel.setIcon(icon);
        pictureLabel.setToolTipText(choices.toString());
        if (icon == null) {
            pictureLabel.setText("Missing Image");
        } else {
            pictureLabel.setText(null);
        }
    }

    /** Returns an ImageIcon, or null if the path was invalid. */
    protected static ImageIcon createImageIcon(String path) {
        java.net.URL imgURL = CheckBoxDemo.class.getResource(path);
        if (imgURL != null) {
            return new ImageIcon(imgURL);
        } else {
            System.err.println("Couldn't find file: " + path);
            return null;
        }
    }

     public static void main(String[] args) {
        JFrame.setDefaultLookAndFeelDecorated(true);
        JFrame frame = new JFrame("CheckBoxDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        CheckBoxDemo newContentPane = new CheckBoxDemo();
        frame.getContentPane().add(newContentPane);
        frame.pack();                   //调整框架的尺寸到一个合适的数值
        frame.setVisible(true);
    }
}