Animated Shapes CPS 004.1, 17 July 2002

You are to write a Java applet that displays a variety of animated shapes. They should each animate differently, but perhaps synchronized into a larger kind of animation. On a computer, animating a shape involves making many tiny changes to an object's attribute quickly over time, or in other words, extending a loop over time. However, instead of writing the loop directly, you will write only the body, or work, of the loop as a specifically named method of a specific class and GP will determine when to call your function repeatedly.

This assignment is meant to familiarize you with the following concepts discussed in class and your reading:

Animation
Instance versus Local variables
Extending GP classes

Specifications

You should animate at least five different shapes within your applet. You should create three different behaviors that each change a different attribute of a given shape, e.g., move to a point, grow for a time, spin, etc. Since there will be fewer kinds of behaviors than shapes, you must make your behaviors flexible enough so they can be parameterized by which shape and amount of change to animate, e.g., spin in a different direction, move at a different speed, or grow at a different rate.

You should do this by creating three classes that extend GP.Behaviors and are added to the shape to animate. You can be creative in determining how each shape animates, but you must implement at least one of each of the following kinds of behaviors:

changes an attribute of the shape forever by extending a GP.Behaviors.Perpetual
changes an attribute of the shape a specific number of times by extending a GP.Behaviors.CountLimited
changes an attribute of the shape for a specific amount of time by extending a GP.Behaviors.TimeLimited

On your applet's web page, you should provide directions that tell the user what behavior to expect for a particular kind of shape.

An example can be seen online here. A worked out example can be seen online here. Note, the Step method for an object that extends any GP.Behavior is never called directly within your code; instead it is called by GP only after it has been added to a shape.

What to Submit

When you are finished, you and your partner should transfer the entire project folder created by Visual J++ to your respective public_html/cps4 folder in the acpub system and update your course web page to link to the newly transferred project using the guidelines given here.