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Help:
Java: Applet Basics |
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It Isn't That Difficult...
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Setting up JAVA applets, though perhaps daunting the first time you do it, is really quite
simple. There are only two types of HTML tags required - both easy
to deal with.The
APPLET tag basically just tells the
browser what applet.class file to use, and how wide and high the applet should be.
(There are additional attributes you can set up, too; but in simplest
use,
that's all there is to this tag.)
The PARAM tag is likewise
simple -- it Names a parameter the JAVA applet needs to run, and provides a
Value for that
parameter. Though a given applet may have anywhere from no PARAM tags to dozens,
still, every PARAM tag takes the very same simple form: just a Name, and a
Value.
In addition to the tables outlining the APPLET tag,
Positioning elements you can use with it, and the PARAM tag, there's also a simple
EXAMPLE below, explained in basic terms.
(All CodeBrain applets
also come with ample demos, pre-made HTML, and detailed 'cheat sheet'
instructions. Most better providers of applets do similarly.)
And please, remember
the CodeBrain maxim: "This is simple -- don't make it
complicated!"
=O=

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The <APPLET> </APPLET> Tag
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Okay,
we know this looks like a nightmare waiting to happen... but guess
what: Most of what you see in the table below is very rarely
used. The basic use of this tag looks like this:
<APPLET
CODE="SomeApplet.class" width="300"
height="200">
...
parameters
-- see example below
...
</APPLET>
Simple enough, eh?
Still, take a few minutes to run through the table below. Though
only Code, Width, and Height are generally needed, you should at least
have an awareness of the rest.
Note that applet tags
aren't case sensitive, by the way... but links and calls to resources
like image files or sound files, etc., absolutely are!
 |
Attribute |
Description |
Usage |
Required? |
Code |
Name of
applet .class file |
Code="Applet.class" |
Y E S |
Width |
Width of applet,
in pixels |
Width = 300 |
Y E S |
Height |
Height of applet,
in pixels |
Height = 150 |
Y E S |
Codebase |
Path to directory where applet resides;
also resources |
Codebase="applets
/"
(that is,
a path) |
ONLY if the .class file is
in a directory other than that of the HTML page |
Alt |
Text displayed in browsers that do not support JAVA, or have JAVA disabled |
alt = "Your browser does not support JAVA" |
NO
- virtually all browsers
in common use now support JAVA; though some users turn it off |
Name |
Applet name |
Name="George" |
ONLY
in special cases, usually with
applets made to communicate with each other or with JavaScript |
Align
|
Positions applet in relation to images and/or text around it, using: Left, Right, Top, Texttop,Middle, Absmiddle,
Baseline, Bottom, Absbottom
|
Align=Right |
NO
-- but these often
neglected attributes are extremely helpful in layout |
Vspace |
Vertical space, in pixels, above and below applet |
Vspace =10 |
NO
-- but helpful in layout |
Hspace |
Horizontal space, in pixels, to left and right of applet |
Hspace=40 |
NO
-- but helpful in layout |
Notes... |

Especially for newcomers to JAVA, it's best to put ALL files related to the applet -- the
.class file, any associated images, text files, and the HTML page -- in the SAME
directory.Do
NOT use Codebase= when setting up an applet. Get
the Applet working FIRST -- then worry about organizational concerns.
Bad pathing -- meaning the
HTML page can't find the applet, or the applet can't find the files it needs -- is
one pf the most common reasons for difficulty in setting up JAVA applets!
=O=
 |

The <PARAM>
Tag
 |
Attribute |
Description |
Usage |
Required? |
NAME |
Name
of the Parameter |
PARAM="WhateverName"
PARAM's vary broadly from applet to applet, depending on the requirements of the individual
applet. PARAM's are absolutely NOT standard, like HTML tags, so
*read* the documentation with every applet!
|
Y E S |
VALUE |
The
Value associated with the Parameter |
VALUE=100
or
VALUE="Image.gif
etc.
VALUE's vary from applet to applet, depending on the requirements of the individual
applet. VALUE variables are absolutely NOT standard, like HTML tags, so
*read* the documentation with every applet!
|
Y E S |
Notes... |
Virtually all applets have one or more parameters -- but it is possible to have an
applet that has none.The NAME of
each PARAM will be different. Take special care to spell and case the NAME exactly
-- typos in parameter names (and values) are the second most frequent cause of difficulty
in setting up applets.
Some VALUE attributes will take multiple values,
for instance:
<PARAM NAME="BackgroundColor" VALUE="255,126,32">
Be careful to include the commas, and never leave spaces!
Note that unlike most HTML tags, the PARAM tag
stands alone, and does NOT use a </param> closing tag.
=O=
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Simple Example
 |
.
<HTML>
<BODY>
<APPLET CODE="CodeBrainSlider.class" WIDTH="360"
HEIGHT="150">
.....<PARAM
NAME="BackgroundColor"
value="255,0,0">
.....<PARAM
NAME="Image1" VALUE="greendog.jpg">
.....<PARAM
NAME="Image2" VALUE="redpig.jpg">
</APPLET>
.
</BODY>
</HTML>
. |
Translation... |
.
What the above HTML code actually says, is: Call the JAVA applet named
CodeBrainSlider.class. Make it 360 pixels wide and 150 pixels high. Make the
BackgroundColor rgb 255,0,0 (that's red). For the first image in the applet, use the
file called greendog.jpg, and for the second one use redpig.jpg.
=O=

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