[CLUE-Tech] Java swing

Wed Dec 27 16:31:05 MST 2000

On Tuesday 26 December 2000 20:47, Jeff wrote:

> What is your javac command that you are using to compile your test program?

Jeff, here's what I've done and how I use javac.  The first three steps work 
fine, but I cannot get step four to work.

First I need to put /usr/jdk-sun1.2.2/bin into my path:
export PATH=/usr/jdk-sun1.2.2/bin:$PATH

I compile and run a simple standalong Java applicaiton:
        javac HelloWorldApp.java
        java HelloWorld

This is the source:

    /**
     * The HelloWorldApp class implements an application that
     * simply displays "Hello World!" to the standard output.
     */
    class HelloWorldApp {
        public static void main(String[] args) {
            System.out.println("Hello World!"); //Display the string.
        }
    } 

That works fine.  It is a standalone application (note the main()).
Now to try it from HTML.  The application changes only slightly:

    import java.applet.Applet;
    import java.awt.Graphics;

    public class HelloWorld extends Applet {
        public void paint(Graphics g) {
                g.drawString("Hello world!", 50, 25);
        }
    }  

Note there is no main(), so it's going to be called from
somewhere else (from HTML).  Here is the file HelloWorld.html:

    <HTML>
    <HEAD>
    <TITLE>Hello World</TITLE>
    </HEAD>
    <BODY>
    <APPLET CODE="HelloWorld.class" WIDTH="160" HEIGHT="310"
    ALT="hello world failed">
    Java is disabled
    </APPLET>
    </BODY>
    </HTML>        

This, step 2, works fine also.
I compile the class with javac HelloWorld.java
Then with a Java-enabled browser, open the file HelloWorld.html
and everything is just fine.  The applet runs, Hello world! shows
up in the browser window.

Now on to swing, step 3:

Here is a simple program which uses swing:

    import java.awt.event.WindowAdapter;
    import java.awt.event.WindowEvent;
    import javax.swing.JFrame;

    public class FrameTest2
    {  public static void main(String[] args)
       {  EmptyFrame frame = new EmptyFrame();
          frame.setTitle("Close me!");
          frame.show();
       }
    }

    class EmptyFrame extends JFrame
    {  public EmptyFrame()
       {  final int DEFAULT_FRAME_WIDTH = 300;
          final int DEFAULT_FRAME_HEIGHT = 300;
          setSize(DEFAULT_FRAME_WIDTH, DEFAULT_FRAME_HEIGHT);

          WindowCloser listener = new WindowCloser();
          addWindowListener(listener);
       }

       private class WindowCloser extends WindowAdapter
           {  public void windowClosing(WindowEvent event)
          {  System.exit(0);
          }
       }
    }  

Note this has a main(), so it can be run directly with java.
So this works:   javac FrameTest2.java; java FrameTest2
Step 3, swing in an application, works fine.

So what works is Java in an application, Java as an applet,
Java with swing in an application, but *not* Java with swing
as an applet.

Now I know my browser can handle swing since I can go to this URL:

http://java.sun.com/docs/books/tutorial/uiswing/start/swingApplet.html

and test it, successfully.  

I need to to run locally, so I download HelloSwingApplet.java from
that page, compile it (javac HelloSwingApplet.java).  I also
download the provided HelloSwingApplet.html from the same page.
I open HelloSwingApplet.html in my drowser, and it just doesn't
run the applet.  It gives me very briefly
"load: class HelloSwingApplet.class not found"
and then "start: applet not initialized"  
I know the .class file is in ~ where the .html file is, so I'm very 
confused.  Is there a search path I need to set up?

What would make my Java-wish come true would be a simple example
of an applet that uses swing and an HTML file that invokes it.
If I can get that to work, the rest should be easy.

-- 
Roger Frank
Ponderosa High School, Colorado