Re: LiveConnect applet crashing after page reload, please help

From: Andrew Thompson <SeeMySites@www.invalid>
Date: Fri Jun 24 2005 - 18:37:37 CEST

On 11 Jun 2005 19:02:19 -0700, DKM wrote:

[ Note: Follow-ups set to comp.lang.java.programmer ]

> The thing works both in IE 6.0 and FireFox 1.4. but with some problems.

I have a stable variant that I tried to add to add
your bug report at Sun..
<http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6289379>

Most of text disappeared, so I will try posting it here..

....
Try this as a potential 'workaround'.

I put '' because it takes a significantly
different approach - performing the bulk
of the element manipultion using JS functions
specially developed for X-browser compatibility.

This example fails when the user specifies
an element id that does not exist.

Developing a more robust script to account
for those sort of errors is left as an
exercise for the reader.

See the sources for further details and notes.

<sscce>
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import netscape.javascript.*;

public class Hello extends Applet implements ActionListener {

private JSObject win;

TextField element;
TextField text;

  public void init() {
    setLayout( new GridLayout(0,1) );
    add(new Label("Element"));
    element = new TextField("para");
    add( element );

    add(new Label("Text"));
    text = new TextField(", some <em>new</em> text");
    add( text );

    Button btn = new Button("Add Text");
    btn.addActionListener(this);
    add( btn );
  }

  public void actionPerformed(ActionEvent ae) {
    setPara();
  }

  public void start() {
    win = JSObject.getWindow(this);
  }

  /** Calls a JS function that changes named
  elements in the current page. */
  public void setPara() {
    try {
      // all sorts of things can go wrong here..
      win.eval( "setPara('" + element.getText() +
        "', '" + text.getText() + "')" );
    } catch (Throwable t) {
      // ..let's find out what.
      System.out.println( "There was a problem, " +
        "see stacktrace for further details" );
      t.printStackTrace();
    }
  }
}
</sscce>

---- index.html ----
<!doctype html public "-//W3C//DTD HTML 4.01 Transitional//EN">

<head>
<meta http-equiv="CONTENT-TYPE" content="text/html; charset=iso-8859-1">
<!--
>From a bug report at Sun - Bug Id.: 6289379
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6289379
LiveConnect Applet crashes on page reload
from a thread on comp.lang.java.help,
Msg Id.: 1118541739.318472.180580@z14g2000cwz.googlegroups.com
http://groups-beta.google.com/group/comp.lang.java.help/msg/35ddca8a2249914a

This version incorporates the getElementWithId(id) function shown here..
http://www.jibbering.com/faq/faq_notes/alt_dynwrite.html#getEl
to deal with browser compatibility issues.
-->
<title>Document manipulation with Javascript/LiveConnect</title>
<script type='text/javascript' SRC='script.js'>
</script>
</head>

<body onload='getApp();'>
<div>
<input type="button" onclick="addElement()" value="Fill"/>
</div>
<!--
http://java.sun.com/products/plugin/1.3/docs/jsobject.html
..lists the <applet> format of the 'mayscript' attribute as below.

The form used in the original page is refered to on that same
page as being appropriate for the <embed> structure only.
Neither the <embed> structure nor the MAYSCRIPT attribute
where ever part of any W3C recommendation.

Note that <applet> was part of HTML 3.2 but is deprecated in HTML 4.0.

I feel the <applet> element is too important and useful to lose
and should be *un*deprecated. But that is another matter.
-->
<applet id="Hello" code="Hello.class" width="100" height="100" MAYSCRIPT>
</applet>

<p id="para">The <P> element (id="para"). Some text</p>
<div id="adiv">The <DIV> element (id="adiv"). Some text</div>

</body>
</html>
---- end index.html ----

---- script.js ----
var app;

/* Calls an x-browser script* developed for inclusion
in the comp.lang.javascript FAQ. * One of several
dealing with document manipulation. */
function getApp() {
app = getElementWithId("Hello");
}

/* Allows the HTML button to invoke the applet's 'setPara()
method. The applet's setPara() method, in turn, invokes the
(JS) setPara(id, txt) function using the current values of
the text fields in the applet. */
function addElement() {
app.setPara();
}

/* The method that changes the element.
Called by both the HTML button and the applet. */
function setPara(id, txt) {
document.getElementById(id).innerHTML =
document.getElementById(id).innerHTML + txt;
}

/* Script obtained from ..
http://www.jibbering.com/faq/faq_notes/alt_dynwrite.html#getEl
See the URL for further discussion. */
function getElementWithId(id){
    var obj = null;
    if(document.getElementById){
        /* Prefer the widely supported W3C DOM method, if
           available:-
        */
        obj = document.getElementById(id);
    }else if(document.all){
        /* Branch to use document.all on document.all only
           browsers. Requires that IDs are unique to the page
           and do not coincide with NAME attributes on other
           elements:-
        */
        obj = document.all[id];
    }
    /* If no appropriate element retrieval mechanism exists on
       this browser this function always returns null:-
    */
    return obj;
}
---- end script.js ----

HTH

-- 
Andrew Thompson
http://www.PhySci.org/codes/  Web & IT Help
http://www.PhySci.org/  Open-source software suite
http://www.1point1C.org/  Science & Technology
http://www.LensEscapes.com/  Images that escape the mundane

Received on Tue Oct 18 02:48:24 2005

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Re: LiveConnect applet crashing after page reload, please help