Java Reference
In-Depth Information
TABLE 12-3 Some Members of the class JApplet ( package javax.swing )(continued)
public void destroy()
//Called by the browser or applet viewer. Informs this applet that
//it is being reclaimed and that it should destroy any resources
//that it has allocated. The method stop is called before destroy.
public void showStatus(String msg)
//Displays the string msg in the status bar.
public Container getContentPane()
//Returns the ContentPane object for this applet.
public JMenuBar getJMenuBar()
//Returns the JMenuBar object for this applet.
public URL getDocumentBase()
//Returns the URL of the document that contains this applet.
public URL getCodeBase()
//Returns the URL of this applet.
public void update(Graphics g)
//Calls the paint() method.
protected String paramString()
//Returns a string representation of this JApplet; mainly used
//for debugging.
Unlike Java application programs, Java applets do not have the method main . Instead,
when a browser runs an applet, the methods init , start ,and paint are guaranteed to be
invoked in sequence. Therefore, as a programmer, to develop an applet, all you have to do
is override one or all of the methods init , start ,and paint . Of these three methods, the
paint method has one argument, which is a Graphics object. This allows you to use the
class Graphics without actually creating a Graphics object. Later in this chapter, when
the class Graphics is presented in detail, you will notice that it is an abstract class;
therefore, you cannot create an instance of this class. For now, all you need to do is import
the package java.awt so that you can use various methods of the class Graphics in
the paint method. To do so, you need the following two import statements:
import java.awt.Graphics;
import javax.swing.JApplet;
Because you create an applet by extending the class JApplet , a Java applet in skeleton
form looks something like this:
import java.awt.Graphics;
import javax.swing.JApplet;
public class WelcomeApplet extends JApplet
{
}
Search WWH ::




Custom Search