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A Java program can be both
an applet and an application:
// ...
public class AppletApplication extends JApplet
{
public void init()
{ ... }
// ...
public static void main(String[] args)
{ ... }
}
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To make it work, the main method must
create a frame for the applet to execute in.
It's convenient to create a frame to use
for this purpose:
// ...
public class AppletFrame extends JFrame
{
public AppletFrame(JApplet applet, int width, int height)
{
setTitle(applet.getClass.getName());
setSize(width, height);
setDefaultCloseOperation(EXIT_ON_CLOSE);
JPanel panel = new JPanel( new BorderLayout() );
getContentPane().add(panel);
panel.add(applet, BorderLayout.CENTER); // Add applet to frame
applet.init(); // Init the applet
setVisible(true);
applet.start(); // Start the applet
}
// ...
}
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So the main method of the
AppletApplication should do the following:
// ...
public class AppletApplication extends JApplet
{
public void init()
{ ... }
// ...
public static void main(String[] args)
{
new AppletFrame(new AppletApplication(), 620, 400);
}
}
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Unfortunately, this is not sufficient. If
the applet tries to execute code like:
getAppletContext()
because there is no applet context in the AppletFrame.
The fix is to implement two interfaces in AppletFrame:
// ...
public class AppletFrame extends JFrame
implements AppletStub, AppletContext
{
// AppletStub methods
public boolean isActive() { return true; }
public URL getDocumentBase() { return null; }
public URL getCodeBase() { return null; }
public String getParameter(String name) { return ""; }
public AppletContext getAppletContext() { return this; }
public void appletResize(int width, int height) {}
// AppletContext methods
public AudioClip getAudioClip(URL url) { return null; }
public Image getImage(URL url) { return null; }
public Applet getApplet(String name) { return null; }
public Enumeration getApplets() { return null; }
public void showDocument(URL url) {}
public void showDocument(URL url, String target) {}
public void showStatus(String status) {}
public AppletFrame(Applet applet, int width, int height)
{
setTitle(applet.getClass.getName());
setSize(width, height);
setDefaultCloseOperation(EXIT_ON_CLOSE);
JPanel panel = new JPanel( new BorderLayout() );
getContentPane().add(panel);
panel.add(applet, BorderLayout.CENTER); // Add applet to frame
applet.setStub(this); // Set up the AppletStub
applet.init(); // Init the applet
setVisible(true);
applet.start(); // Start the applet
}
// ...
}
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Another possibility is to use inheritance
to allow any applet to be executable as an application:
public class CalculatorAppletApplication
extends AppletApplication
{
public static void main(String[] args)
{
new AppletFrame(new CalculatorApplet(), 150, 100);
}
}
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