Java Reference
In-Depth Information
applet method
paint
. This method takes a
Graphics
object as its single argument and
is not called directly by the applet, but is executed by the Web browser. In Swing
applets, however, the required components are added to the applet's surface within
method
init
(also executed implicitly by the browser) and
no painting should be
specifi ed
(though there is nothing that actually prevents us from doing so).
Example
Taking the simplest possible example, we'll create an applet that displays a greeting
to the user. In order to avoid specifying painting onto the applet's window, we can
use a
JLabel
and add this to the applet (within method
init
, of course), just as we
would do for the application
JFrame
in a GUI application.
Remember that the applet class must extend class
JApplet
.
import java.awt.*;
import javax.swing.*;
public class AppletGreeting extends JApplet
{
public void init()
{
JLabel message =
new JLabel("Greetings!",JLabel.CENTER);
//Default layout manager for
JApplet
is
//
BorderLayout
…
add(message,BorderLayout.CENTER);
}
}
Just as we would do for a Java application, we save this applet with the name
AppletGreeting.java
. We then compile it in the usual way:
javac AppletGreeting.java
However, before we can run it, we must place it in an HTML page via the
<APPLET>
tag. This tag has three mandatory attributes (as well as a number of
optional ones):6
CODE
(specifying the name of the applet's
.class
fi le);
WIDTH
(specifying the width of the applet, in pixels);
HEIGHT
(specifying height of the applet, in pixels).
As will be the case for all subsequent applets in this chapter, we shall employ a
minimal HTML page:
<HTML>
<APPLET CODE = "AppletGreeting.class"
WIDTH = 300
HEIGHT = 150>
</APPLET>
</HTML>
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