helphandler.java

编写程序

/*
 * @(#)HelpHandler.java	1.4 03/12/19
 * 
 * Copyright (c) 2004 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:
 * 
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 * 
 * -Redistribution 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, Inc. or the names of contributors may 
 * be used to endorse or promote products derived from this software without 
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL 
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, 
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY 
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, 
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */


import javax.help.*;
import java.util.*;
import java.net.*;
import javax.swing.*;
import java.awt.event.ActionEvent;
import javax.jnlp.DownloadService;
import javax.jnlp.DownloadServiceListener;
import javax.jnlp.ServiceManager;
import javax.jnlp.UnavailableServiceException;

public class HelpHandler {

   static private DownloadService _ds = null; 
    
    static public final String helpsetName = "HolidayHistory.hs";
    
    static public HelpBroker _hb = null;
    
    static public void  showHelp(final ActionEvent evt) {
	new Thread() {
	    public void run() {
		showHelpHelper(evt);
	    }
	}.start();
    }
    
    static public void showHelpHelper(ActionEvent evt) {
	checkForDownload();
	initializeHelpSystem();
	new CSH.DisplayHelpFromSource(_hb).actionPerformed(evt);
    }
    
    static public synchronized void initializeHelpSystem() {
	if (_hb != null) return;
	try {
	    JOptionPane pane = new JOptionPane("Initializing help system. Please Wait...",
					       JOptionPane.INFORMATION_MESSAGE);
	    JDialog dialog = pane.createDialog(null, "WebPad Help System");
	    dialog.setModal(false);
	    dialog.setVisible(true);
	    
	    HelpSet hs = null;
	    ClassLoader cl = HelpHandler.class.getClassLoader();
	    URL hsURL = HelpSet.findHelpSet(cl, helpsetName);
	    hs = new HelpSet(cl, hsURL);
	    _hb = hs.createHelpBroker();
	    _hb.initPresentation();
	    dialog.setVisible(false);
	} catch (Exception ee) {
	    System.out.println("HelpSet " + helpsetName + " not found");
	    return;
	}
    }
    
    static private void checkForDownload() {
	try {
	     _ds = (DownloadService)ServiceManager.lookup("javax.jnlp.DownloadService");
        } catch (UnavailableServiceException e) {
          _ds = null;

        }

        if (_ds != null) {
        try {
	    
           if (_ds.isPartCached("help")) {
		System.out.println("Help System is cached");
		return;
	    }
	    _ds.loadPart("help", _ds.getDefaultProgressWindow());
	  } catch(Exception e) {
            e.printStackTrace();
	  }
        } 
  }
}