Java Reference
In-Depth Information
If this HTML page is saved with the name Greeting.html , then the contained
applet may be executed by loading the HTML page into the appletviewer with the
following command:
appletviewer Greeting.html
N.B. This example assumes that both Greeting.html and AppletGreeting.class
are in the current folder. If AppletGreeting.class is in a sub-folder, then the CODE
attribute must specify the relative path. For example:
CODE = "folder1\folder2\AppletGreeting.class"
For a directory elsewhere, attribute CODEBASE must be used to specify that
directory. For example:
CODEBASE = "..\otherfolder"
(Attribute CODE must still also be used to specify the applet's .class fi le, of course.)
The output from this applet under the appletviewer is shown in Fig. 12.1 below.
Fig. 12.1 Output from
AppletGreeting under the
In order to run a Swing applet in a browser, we must have the Java Plug-in
installed and the browser must know that it is to use this plug-in (rather than the
JVM). Both Chrome and IE9 will automatically use the Java Plug-in when accessing
Swing applets. The output from each of these when referencing Greeting.html is
shown in Figs. 12.2 and 12.3 . (Note the grey background, as for the appletviewer,
now serving the purpose of distinguishing the applet from the HTML page.)
The Internal Operation of Applets
As its name implies, method init carries out any initialisation required by the applet, such
as initialisation of variables or loading of images. Since applets cannot call the paint
method directly, it is necessary to circumvent direct painting via the following steps:
￿ create a subclass of JPanel (within the applet body) and place the painting code
inside method paintComponent of this class;
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