CSC 121A Lab 5 - Spring 2005

Thursday, February 3, 2005
Due: Wednesday, February 9, 2005, 5:00PM

Answer all numbered and bulleted questions. Upload your answers and program files to the VikingWeb coursework section. Besides uploading your written answers to the VikingWeb, please turn in a printed copy either in class on the due date or leave a copy in the box outside my door later on during the day. (You may turn in the printed copies later than 5PM on the due date, but the files must be uploaded to VikingWeb at or before 5PM.)

You may work in pairs for all parts of this assignment, including the homework exercises. Remember also, your code will be graded for robustness - i.e. how well it handles in cases of erroneous input, etc. Be sure to think about things that could go wrong and try to deal with them.

Sample Applets Provided with the Java SDK

The Java SDK comes with several demonstration applets and their source code. It can be interesting and helpful to read this source code if you want to learn new and exciting features of Java. We will not be doing anything further with these applets in this course, but you may want to browse the examples in the folder:

C:\Program Files\Java\jdk1.4.2\demo

(In general, the example files are in the demo directory of wherever you installed the Java SDK. The applets can also be accessed online at this site.)

To run the applets, either find the appropriate HTML file in the directory of the applet you wish to view and open it with the web browser. Or else, if Java is not installed in the web browser, or there are security restrictions on the browser, you can view the applets by running the appletviewer program from the terminal (command window).

For this lab, just try running the TicTacToe and DrawTest applets and take a brief look at their source code. You can look in detail at their source code and the other applets at your leisure.

• The DrawTest class (in DrawTest.java) contains a main() method as well as an init() method. We learned in class that applets only use an init() method. Why do you think there is a main() method in this class?
   
• What is the Vector class that is used in the DrawPanel class?
   
• What is the purpose of the x1, y1 fields in the DrawPanel? What is the purpose of the x2, y2 fields? (Note: the two pairs are used in different ways.)
   

Animation

Download the following program and image data files: LogoAnimator.java, LogoAnimatorJPanel.java, images.zip. (The images archive should be uncompressed into a directory named "images" in the same directory as the Java files.)

This program displays an animated logo by displaying a different image every 50 milliseconds, using the Swing Timer class. Run the program, look through the source code, then:

• Convert this application into an applet. All you should need to do is write a class called LogoAnimatorApplet, extending JApplet, that adds the LogoAnimatorPanel panel to itself, with code to start and stop the animation as appropriate (i.e. define the methods init(), start(), and stop() appropriately for your applet). You will also need to write an HTML web page in which the applet is embedded. Call your HTML file "LogoAnimator.html".
   

Applet Parameters

The HTML applet tag embedded in a web page has a way of specifying parameters for use by the applet. Within the <APPLET>...</APPLET> on can specify optional PARAM elements with a name and value. Look at the source for this web page and the corresponding applet code to see how this works: HelloApplet.html, HelloApplet.java. (To view the source of the web page, there is usually a menu command "View Source" somewhere under the "View" menu of your browser.

• Modify the HelloApplet.java applet so that it also accepts an optional parameter allowing one to specify the size of the font. To change the font size, you can use the getFont method of the Graphics class to obtain the current font. Obtain a modified version of the font using the appropriate deriveFont method of the Font class to change the size. Then use the setFont method in the Graphics class to update the font of the applet's panel.

Simple Game Skeleton

The following files make up the skeleton for what could be developed into a simple arcade game.

• GameApplet.html: The HTML file for the applet
• GameApplet.java: The main applet class
• GamePanel.java: The class for the actual display of the game play area; also contains handler for keyboard input, and manages the animation
• MovingObject.java: The abstract superclass for objects that need to move in the game. This class already contains equations for figuring out how to update the x,y coordinates of an object based on its velocity/acceleration. It is abstract because it doesn't implement the draw method to describe how to draw the actual object
• Ship.java: A concrete subclass of MovingObject that provides a very primitive image of a ship

Download, compile, and view the applet. A homework assignment (below) is left for you to exercise your creativity.

Homework Exercises

• Scrolling Marquee Applet: Create a Java applet that scrolls a message from left to right across the display. The text should be displayed in a continuous loop, so that after it disappears at one end, it reappears at the beginning. It should be possible to specify the text to be displayed using the parameter elements of the applet tag. Besides your Java source code, submit also your corresponding HTML file.
   
• Extend the game skeleton above in some creative way. You do not have to make anything close to a real, functional game. Just add at least one simple feature to the applet, for example:
  • The ability to have two ships on the screen, controlled by two players
  • The ability to shoot bullets from the ship (bullets can also just subclass the MovingObject class as necessary)
  • Meteors flying around the screen, that may crash into the ship
  • A better image for the ship, including, for example, a fiery exhaust behind the ship whenever it is accelerating
  • Any other cool feature you can think of :)
  
   
• Project Stage 2: due next week. See the project description (click here).

Based on material from Deitel & Deitel, Java How to Program, 6e.

Last modified: Wed Feb 2 21:18:05 EST 2005