JAVA

Deploying Multiple Java Applets as One

In this conclusion to a three-part series covering the three different kinds of deployment frameworks you can use with Java games, you'll learn how to deploy multiple Java applets as if they were all one applet. This article is excerpted from chapter two of Advanced Java Game Programming, written by David Wallace Croft (Apress; ISBN: 1590591232).

Author Info:

By: Apress Publishing

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April 24, 2008

TABLE OF CONTENTS:

· Deploying Multiple Java Applets as One
· MultiAppletNews
· Lifecycle
· MultiApplet
· CroftSoftCollection

An instance ofJEditorPanefrom core packagejavax.swingis used to display the initial web page in the first panel of the multi-applet framework. The caret position is set to zero so that the top of the page will be displayed instead of scrolling to the bottom when the page is initially loaded. AHyperlinkListeneris added so it can intercept mouse clicks on hypertext links and download and display the appropriate web page. For a tutorial on usingJEditorPaneandHyperlinkListener, I recommend Chapter 4, “JEditorPane and the Swing HTML Package” of Core Swing Advanced Programming by Kim Topley.⁵

if ( newsPage != null )
{
    try
    {
      final URL newsURL = new URL ( newsPage );

      new Thread (
        new Runnable ( )
        {
          public void run ( )
          {
            try
            {
              jEditorPane.setPage ( newsURL );
            }
            catch ( Exception ex )
            {
              ex.printStackTrace ( );
            }
          }
        } ).start ( );
    }
    catch ( MalformedURLException ex )
    {
      ex.printStackTrace ( );
    }
}
}

When initialized,MultiAppletNewsattempts to download the web page atnewsURL. This is launched in a separate thread because it might stall indefinitely when there is a network problem.

private void processHyperlinkEvent ( HyperlinkEvent hyperlinkEvent )
//////////////////////////////////////////////////////////////////////
{
    try
    {
      if ( hyperlinkEvent.getEventType ( )
        == HyperlinkEvent.EventType.ACTIVATED )
      {
        if ( hyperlinkEvent instanceof HTMLFrameHyperlinkEvent )
        {
          HTMLDocument htmlDocument
            = ( HTMLDocument ) jEditorPane.getDocument ( );

htmlDocument.processHTMLFrameHyperlinkEvent (
            ( HTMLFrameHyperlinkEvent ) hyperlinkEvent );
        }
        else
        {
          URL url = hyperlinkEvent.getURL ( );

          if ( appletContext != null )
          {
            appletContext.showDocument ( url, "_blank" );
          }
          else
          {
            try
            {
              JnlpLib.showDocument ( url );
            }
            catch ( UnsupportedOperationException ex )
            {
              jEditorPane.setPage ( url );
            }
          }
        }
      }
    }
    catch ( Exception ex )
    {
      ex.printStackTrace ( );
    }
}

Clicking a hyperlink generates aHyperlinkEvent. The destinationurlcan then be retrieved from theHyperlinkEventand displayed. To display the web page, three different mechanisms are attempted. If anAppletContextis available, the code uses it to show the URL in a new browser window. Otherwise, it attempts to launch an external browser using JNLP. If this also fails, the code usesJEditorPaneto display the web page. Note that the ability ofJEditorPaneto display web pages is limited compared to most browsers.

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