Version of 28 January 2008

Overview of the programming presented here - Java Swing

There are a variety of languages, IDEs, and systems that allow you to create interactive applications. I will concentrate on Java Swing, a facility I have used for years and am therefor reasonably familiar with. I can more efficiently illustrate interactive system development for you by focusing on Swing. Java was invented to create applets in browsers, so it had graphics from day one, as well as the ability to download and run code in browsers. The graphics evolved into Swing so it is possible to build substantial applications in Swing. Though there are problems associated with this approach, Swing is still a fine way to experiment with interactive paradigms without being drawn into the full complexities of developing for a particular OS.

Getting Java on Your Machine - Swing comes with it

You need to have Java on your machine - having Java 6 makes your life a bit simpler, as I'll explain, but all the generally available demos work just fine in Java 5 and even Java 4. If you go to a console or terminal window and type
java -version
you'll either get a version number or an error, meaning Java is installed or not. For example, on my Mac and Windows respectively, I get:

~: java -version
java version "1.5.0_07"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_07-164)
Java HotSpot(TM) Client VM (build 1.5.0_07-87, mixed mode, sharing)

C:\Documents and Settings\Robert Futrelle>java -version
java version "1.6.0_02"
Java(TM) SE Runtime Environment (build 1.6.0_02-b06)
Java HotSpot(TM) Client VM (build 1.6.0_02-b06, mixed mode, sharing)

If, for some reason, you don't have Java on your machine, it's easy enough to download and install it. Go to this site. Note that the Mac is in a different category. Since Apple has a proprietary interactive interface on their systems, Sun does not directly furnish a Java download for the Mac. But they do point you to the Apple site. It should be on your Mac, though you could conceivably have an old version needing updating.

Learning about Swing

There is a full and up-to-date tutorial on Sun's Java site, as well as thousands of pages of useful information about Swing on the web.

Running the Swing Demos

Sun has a collection of over 50 demos on this page that you can run. They offer you a number of options:

• If you have Java 6 on Windows or Linux, or a pre-release of 6 on the Mac, you can simply Launch the app, left column on the demo page. This downloads and runs the app for you.
• Else you can download the source of any demo app (often a single source file) and compile and run it from the command line or your favorite IDE such as Eclipse or the NetBeans IDE.
• You can also download a zip file that has the sources, any images needed and all the metafiles for a full NetBeans IDE project. (I chose the middle route of downloading the zip and moving the source files I wanted to an Eclipse project.)

There's another omnibus demo that shows you all the different things available in Swing. This version runs in a browser and doesn't require Java 6.

On this page, you'll find a Java Web Start version that downloads the SwingSet Demo and runs it as an application. The non-javascript version worked for me on the Mac, and it runs straight on Windows, and presumably Linux. Experiment.

To give you the flavor of all this, here's the intro screen for the SwingSet Demos. The toolbar at the top gives you a choice of fifteen different demos.

Here's how simple Swing code can be:

package components;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

/* FrameDemo.java requires no other files. */
public class FrameDemo {
    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("FrameDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JLabel emptyLabel = new JLabel("");
        emptyLabel.setPreferredSize(new Dimension(175, 100));
        frame.getContentPane().add(emptyLabel, BorderLayout.CENTER);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

Which produces this, when launched on Windows:

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