Computer Science II, Lab 08

Tuesday, October 9th

Letting Users Choose the Color of the CannonBall

Introduction

• This lab gives you a chance to write your own Java class and then to integrate the new class into an existing application - the CannonWorld game.
• Because I want to talk about this code in class tomorrow, your materials from this lab are due before class starts on Wednesday.
• As we have done other times this semester, you may elect to work with a partner.

Tasks

1. Start by downloading the starter code for this lab.  Look at the code so you can see how this is different from the code distributed earlier.  The main changes are
   • There is a new Instance Variable in CannonWorld.  This variable holds an instance of a class called ColorWheel.
   • There are two constructors for CannonWorld.  The first sets up the CannonWorld with the ColorWheel IV set to null.  The second expects a ColorWheel as a parameter and uses this to set the wheel IV.
   • In the drawCannonBall() method, the color of the cannonball is changed _IF_ the ColorWheel exists.
   • I have also provided you with a VERY raw skeleton of the ColorWheel class so that the code will still compile and run.

    

2. Your first real task is to make it so that the ColorWheel class has real functionality.

   Recall that last semester you worked with Pixels, each of which knew their Color.  The Color class includes a three-argument constructor that lets the creator of the Color object define a color based on saturation values of red, green, and blue pigment, respectively. Each argument must be an int between 0 and 255, inclusive.

   A ColorWheel is a window with a large, stationary Ball in its center. It has sliders for the red saturation value (left), the green saturation value (top), and the blue saturation value (right). It also has textual "labels" to help the user keep them straight.  Each label contains the color represented by the slider and the color's current value. 

   When the user moves a slider, the saturation value for the associated color changes, the ball changes color in the window, and the color's label displays the value of the slider.

   A ColorWheel responds to the public message getColor() by returning its current color as a Color. A ColorWheel also uses this method to compute the new color of the ball in its paint() method.

   [Note: While I use the term "Label" above, you are not actually required to use the JLabel class.  You may use drawString like Budd does in CannonWorld.  Of course, if you prefer, you may use JLabel - probably placed with a scrollbar inside of a JPanel and then using BorderLayout to place the Panel.  drawString() is probably easier, but not as pretty.  JPanel is probably more complicated, but gives you cleaner results (perhaps).]

    

   Test this class using a simple demo application class before proceeding to the next task.

    

3. Modify the CannonWorldDriver class to create a ColorWheel and send it to the CannonWorld as a parameter.  If you get things set up correctly you should be able to control the color of the ball at all times.

 

4. Go back through your ColorWheel class and double check whether you actually NEED all of the instance variables you have declared.  My guess is that many of you have created 7-10 instance variables in the ColorWheel class while only a handful (3 or 4?) are actually necessary..

NOTE:

• When you run the program, you can simply move the window that ends up on top so that you can see both, and then arrange the windows any way you like.
• Or you could poke around with Swing to figure out how to tell a window to open at a particular location on the screen. This approach will take more time, but it will also give you a chance to learn more about Swing!

I prefer that you use the second approach.

Deliverables

Using the homework submission system, upload:

• ColorWheel.java

Be sure that your submission follows all homework submission requirements.