Special Effects and Game Development
in Java(TM) -Applet parameters
by Anibal Wainstein
4.1 Applet parameters
The Java language would never have had such a big breakthrough
on the Internet if it had not been for the possibility to
configure Java applets. Without configurable Java applets,
the Java technology would have stayed at the hands of the
developers and never got to the web designers. The applet
parameters is what makes an applet recyclable and available
for everybody. It is a glorious feeling to randomly surf into
a homepage that is using the applet that you have developed
and reconfigurated. With parameters you can change almost
anything in an applet such as the images used, colors, texts,
font styles and more. Parameters also simplify your work as
a programmer due to the simplicity to change parameter values
and not having to change variables directly in the source
code.
4.1.1 Working with getParameter()
It is very simple to read a parameter. Look at the following
HTML code:
<APPLET CODE="myapplet.class" WIDTH=200 HEIGHT=100>
<PARAM name="myparameter" value="Long live Java!">
</APPLET>
In HTML, PARAM is used to specify a parameter,
where "name" stands for the name of the parameter
and "value" for the content. The method getParameter()
always return a String and can, for instance, fetch "myparameter"
like this:
String oneparameter=getParameter("myparameter");
Now "oneparameter" will contain
the phase "Long live Java!". You may have how
many parameters as you like, theoretically. However note
that each parameter must have an unique name label. To simplify
your work and to make your source code easy to read you
should always read parameters in the init() method. The
alternative is to put these lines in the run() method which
will make your code difficult to read.
4.1.2
How to read an integer as a parameter (getIntegerParameter())
As we saw in the last section, getParameter()
always return a string. If you want to read an integer instead,
then you can use the following method:
public int getIntegerParameter(String name, int base)
{
String value=getParameter(name);
int intvalue;
try {intvalue=Integer.parseInt(value,base);}
catch (NumberFormatException e) {return 0;}
return intvalue;
}
The method above is always good to have in
an configurable applet, so you should always have the habit
of pasting these lines into your source code, if you are
going to make such an applet. The Integer class in Java
is used to handle integers, but please note carefully now:
"Integer" is NOT the same as "int".
Integer is a class with methods while int is just a data
type. A useful method that Integer has, is the static method
parseInt() that converts a String to an integer ("int").
The other argument in parseInt() is the number base that
may be decimal or hexadecimal (number base 10 or 16 respectively).
The decimal number base is the normal number base system
you use on your everyday life. If you are a web designer
then you should also know the hexadecimal number system
when you specify colors (that is if you write the HTML code
yourself without a graphical HTML editor). You will later
see the use of this when we specify colors for the textscroll
applet.
Next Page >>
|
 | |
|
