Interactive Shapes CPS 004.1, 19 July 2002

You are to write a Java applet that draws shapes in reaction to being clicked on. When you add a Behavior to any kind of shape, GP automatically calls its Step method repeatedly (until the behavior is done). Similarly, you can add a Reaction to any kind of shape that allows it to react to someone using your applet (e.g., by clicking the mouse button or pressing a key). Once you add a Reaction to a shape, GP will automatically call its React method when the given event occurs within the shape. Note, if you add a reaction directly to the applet, the React method will be called when an event occurs within the applet, but outside of any other shape visible in the applet.

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

Interacting with the user of your program
Randomness

Specifications

You are to make an applet that creates a shape centered at the mouse's current position when the user clicks the mouse button within the applet (but outside of any other shape). The particular shape created should depend on where in the applet this mouse was clicked. (This simplest example is that an oval is created if clicked in the top half and a rectangle is created if clicked in the bottom half.)

Different kinds of shapes should react differently when clicked upon. For example, a rectangle may change color when clicked, a triangle may spin around, and an oval may create a second shape that falls to the bottom of the applet.

You can be creative in determining how each shape responds to the user, but you must implement at least one of each of the following kinds of reactions:

changes an attribute of the shape (e.g., darkens it, turns it, moves it, grows it, hides it, etc.)
adds a conditional (not perpetual) behavior to the shape (i.e., spins it once around, explodes (grows) it to a specific size, moves it around in a circle)
creates a new kind of shape that has a behavior (i.e., a spinning triangle, a falling drop, etc.)

On your applet's web page, you should provide directions that tell the user what behavior to expect when clicking on each shape.

An example can be seen online here. A simpler example is worked out here. Note, the React method for an object that extends GP.Reactions.MouseClicked is never called directly within your code; instead it is called by GP only when the user has pressed and released the mouse button within the given shape to which you have added the reaction.

Extra Credit

You are to make an applet that creates a random kind of shape centered at the mouse's current position when the user clicks the mouse button within the applet (but outside of any other shape). The shape's other attributes should also be randomly chosen. As above, different kinds of shapes should react differently when clicked upon.

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.