Dreamweaver.MX.1002004.The.Missing.Manual [Electronic resources] نسخه متنی

13.4 Java Applets

A few years ago, it seemed that the whole world was going Java crazy. Created by Sun
Microsytems, this powerful programming language seemed to offer an end to crossplatform
problems. Programs written in Java can run on any operating system: Mac,
Unix, Windows, whatever. Java also offered programmers the opportunity to write
sophisticated applications that could run in the form of a compact file, called an applet,
within any browser. Java applets can provide sophisticated graphics and user interface
elements that go well beyond what HTML can do (Figure 13-8). In fact, Java can be used not only for graphics and multimedia, but to build complete applications like
word processors, spreadsheets, or mortgage calculators that can live right in a Web
page. For loads of sample applets, visit
www.javaboutique.com
.

In this example,
a Java applet lets
you interactively
determine whether
your body mass
is appropriate
for your age and
height. Through the
use of custom interface
elements (such
as the sliders under
the height and
weight columns),
you control the
size of the "man"
and receive instant
feedback in various
form fields. (In this
example, only the
area between the
two horizontal rules
is the actual applet.
Everything else is
HTML.)

In the end, Applets didn't make as big a splash on Web pages as industry forecasters
originally thought. One of Java's limitations is that its applets don't work unless a
Web page visitor has a special software program called a Java Virtual Machine. This
program translates the Java code into instructions appropriate for the visitor's particular
operating system. As with plug-ins, virtual machines require lengthy downloads
and installations that scare off many potential users. In addition, unlike JavaScript,
which is fairly easy to learn, Java is not for the faint of heart. It's a complex language
that requires a lot of skill and practice to do well.

But when the time comes that you've been handed a Java applet for insertion onto,
say, a client's page, here's how to do it.

To insert a Java applet, choose InsertMediaApplet, or choose Applet from the
Media menu on the Common tab of the Insert bar. When the Select File dialog box
appears, find and double-click the Java applet file you want to insert. (Java applets
have a .class or .jar extension.)

After you insert it, the applet appears on your Web page as a gray box with a coffee
cup logo in the middle. Unfortunately, you can't preview it within Dreamweaver;
press the F12 key to see it run in your Web browser.

13.4.1 Applet Properties

You set properties for applets using the Property inspector (see Figure 13-9), just
as for any HTML object. The name, margins, alignment, and width/height controls
work just as they do for Flash movies (see Section 13.1.2). Java applets, however, offer a
few specialized controls:

Code. The name of the applet file appears in the Code field. If you wish to use a
different file, click the folder icon and select another applet.

Base. The Base field lists the folder that contains the applet file. When you insert
an applet, Dreamweaver automatically fills in this field.

Alt. For the benefit of visitors whose browsers don't support Java (or who have
turned Java off), you can provide an alternative image or text description. Type
the text in the Alt field, or click the little folder icon and select a GIF or JPEG file
that will appear in place of the Java applet. The image will appear automatically
if the Java Virtual Machine isn't installed.

Some applets may have properties in addition to the ones listed in the Property inspector.
To add these properties, click the Parameters button. For example, the applet
ticker.class shown in Figure 13-9 produces a ticker-tape display on a Web page. In order
to let the applet know what message it needs to present, you must add a parameter
called message. The value of that parameter would be the message: "Welcome to my
home page. This ticker-tape display is truly annoying, isn't it?"

In the Properties
inspector
for a Java
applet, a new
Parameters button
appears.