componenteventdemo.java

java tutorial.sun公司官方出品。java入门书籍。最新版

/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     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 Sun Microsystems nor 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
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */ 

package events;

/*
 * ComponentEventDemo.java requires no other files.
 */

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

public class ComponentEventDemo extends JPanel
                                implements ComponentListener,
                                           ItemListener {
    static JFrame frame;
    JTextArea display;
    JLabel label;
    String newline = "\n";

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

        display = new JTextArea();
        display.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(display);
        scrollPane.setPreferredSize(new Dimension(350, 200));

        JPanel panel = new JPanel(new BorderLayout());
        label = new JLabel("This is a label", JLabel.CENTER);
        label.addComponentListener(this);
        panel.add(label, BorderLayout.CENTER);

        JCheckBox checkbox = new JCheckBox("Label visible", true);
        checkbox.addItemListener(this);
        checkbox.addComponentListener(this);
        panel.add(checkbox, BorderLayout.PAGE_END);
        panel.addComponentListener(this);

        add(scrollPane, BorderLayout.CENTER);
        add(panel, BorderLayout.PAGE_END);
        frame.addComponentListener(this);
    }

    public void itemStateChanged(ItemEvent e) {
        if (e.getStateChange() == ItemEvent.SELECTED) {
            label.setVisible(true);

            //Need to revalidate and repaint, or else the label
            //will probably be drawn in the wrong place.
            label.revalidate();
            label.repaint();
        } else {
            label.setVisible(false);
        }
    }

    protected void displayMessage(String message) {
        //If the text area is not yet realized, and
        //we tell it to draw text, it could cause
        //a text/AWT tree deadlock. Our solution is
        //to ensure that the text area is realized
        //before attempting to draw text.
       // if (display.isShowing()) {
	    display.append(message + newline);
            display.setCaretPosition(display.getDocument().getLength());
        //}
    }

    public void componentHidden(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Hidden");
    }

    public void componentMoved(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Moved");
    }

    public void componentResized(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Resized ");            
    }

    public void componentShown(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Shown");

    }

    /**
     * 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.
        frame = new JFrame("ComponentEventDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        JComponent newContentPane = new ComponentEventDemo();
        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();
            }
        });
    }
}