htmldisplay.java

Besides enhanced looks and advanced features, one of the best things about Swing is its pluggable lo

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.Document;
import java.net.URL;
import java.io.*;
import java.awt.Cursor;

public class HTMLDisplay extends JScrollPane implements HyperlinkListener
{
		// for displaying the HTML help pages, forms the display area of the app
	private	JEditorPane edit;

//******************************************************************************************	
// Function Name : HTMLDisplay() => the default constructor
// Parameter : None	
//	
// Creates and adds a JEditorPane, adds HyperlinkListener to it, and displays the 
// default help page in it.
//	
//******************************************************************************************
	
	public HTMLDisplay()
	{
		edit = new JEditorPane();
		edit.setEditable(false);
		edit.addHyperlinkListener(this);
		
		getViewport().add(edit);
		
		File file = new File(Theme.THEME_HELP);
		showURL("file:"+file.getAbsolutePath());		
	}

//******************************************************************************************	
// Function Name : hyperlinkUpdate(HyperlinkEvent e)
// Parameter : HyperlinkEvent e
// Returns : None
//	
// Retrieves and displays a new URL whenever a  link in the HTML page is clicked. Method of
// HyperlinkListener. 
//	
//******************************************************************************************
	
	public void hyperlinkUpdate(HyperlinkEvent e)
	{
		if (HyperlinkEvent.EventType.ACTIVATED == e.getEventType()) 
		{
	    		// when a link is cliked page display is differed slightly to ensure
	    		// proper evet dispatch and paint
	    	Cursor c = edit.getCursor();
			Cursor waitCursor = Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR);
			edit.setCursor(waitCursor);
	    	SwingUtilities.invokeLater(new URLLoader(e.getURL(), c));
		}
	}

//******************************************************************************************	
// Function Name : showURL(String url)
// Parameter : String url
// Returns : None
//	
// Displays the URL passed to it in the JEditorPane, in case of error, shows error message box
//	
//******************************************************************************************
	
	public void showURL(String url)
	{
		Document doc = edit.getDocument();
		try{
				edit.setPage(url);		
		}catch(IOException e)
		{
			edit.setDocument(doc);
			System.out.println(e);	
			JOptionPane.showMessageDialog(this, "Couldn't open page : " + url);
			getToolkit().beep();
		}
	}	
	
//******************************************************************************************	
// Inner Class : URLLoader
//
// The inner class which loads the URL in its run method. Implements runnable.
// Used with SwingUtilities.invokeLater() method
//	
//******************************************************************************************
	
	class URLLoader implements Runnable
	{
		private URL url;
		private Cursor cursor;
		
		URLLoader(URL u, Cursor c)
		{
			this.url = u; 
			this.cursor = c;
		}
		
		public void run()
		{
				//after PAINT is done
			if(null == url)
			{
				edit.setCursor(cursor);
			}
			else
			{
				showURL(url.toString());
				url = null;
					// to show normal cursor
				SwingUtilities.invokeLater(this);
			}
		}
	}
}