Java核心技术II-第6章-跟踪文本框中的修改-源代码

Java核心技术II-第6章-跟踪文本框中的修改-源代码，在博文的最后有运行效果图。

 

package javaee.vii.ch06;

import javax.swing.JFrame;

/**
 * 
 * @author lcwell
 */
public class ChangeTrackingTest {

    public static void main(String[] args) {
        JFrame frame = new ColorFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

 

package javaee.vii.ch06;

import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;

/**
 * A frame with three text fields to set the background color.
 *
 * @author lcwell
 */
public class ColorFrame extends JFrame {

    public ColorFrame() {
        setTitle("ChangeTrackingTest");
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

        DocumentListener listener = new DocumentListener() {
            @Override
            public void insertUpdate(DocumentEvent event) {
                setColor();
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                setColor();
            }

            @Override
            public void changedUpdate(DocumentEvent e) {

            }
        };
        panel = new JPanel();
        panel.add(new JLabel("Red:"));
        redField = new JTextField("255", 3);
        panel.add(redField);
        redField.getDocument().addDocumentListener(listener);
        
        panel.add(new JLabel("Green:"));
        greenField = new JTextField("255", 3);
        panel.add(greenField);
        greenField.getDocument().addDocumentListener(listener);
        
        panel.add(new JLabel("Blue:"));
        blueField = new JTextField("255", 3);
        panel.add(blueField);
        blueField.getDocument().addDocumentListener(listener);
        
        add(panel);
        pack();
    }

    /**
     * Set the background color to the values stored in the text fields.
     */
    public void setColor() {
        try {
            int red = Integer.parseInt(redField.getText().trim());
            int green = Integer.parseInt(greenField.getText().trim());
            int blue = Integer.parseInt(blueField.getText().trim());
            panel.setBackground(new Color(red, green, blue));
        } catch (NumberFormatException e) {

        }
    }

    private JPanel panel;
    private JTextField redField;
    private JTextField greenField;
    private JTextField blueField;
    private static final int DEFAULT_WIDTH = 220;
    private static final int DEFAULT_HEIGHT = 80;
}

 运行效果：