SA-5, due Oct 7

This assignment gives you practice creating listeners to animate an applet.

Assignment

Your assignment is to modify a Checkerboard applet from so that whichever square you click on flashes between its normal color and yellow, with the change to or from yellow occurring every half second (i.e., every 500 milliseconds).

You can play with my implementation if you like:

Start with the applet Checkerboard.java. This applet draws a checkerboard. You should read it carefully to figure out how it works.

Here are some design ideas that you might find useful. You should define constants (i.e., final variables) as appropriate.

As with the ClickAMac applet from lecture, use an instance variable to remember where the mouse was clicked; set this instance variable in the mouseClicked method.

To implement the flashing behavior, you'll of course need to create a Timer object and have the appropriate actionPerformed method called every 500 milliseconds. Figure out a way to know whether or not to paint the yellow square, and what to do whenever the Timer rings.

In your paintComponent method, draw the entire checkerboard. After you've drawn the checkerboard, if a point has been clicked, and if you should draw the square in yellow where you clicked, do so. There will be a brief moment after the checkboard is drawn and before the yellow square is drawn, but it is so brief that nobody will ever notice.

You are free to make inner classes for listeners, to let the applet itself act as a listener, or to let the canvas act as a listener.

Given a Point—let's say that it's referenced by clickPoint—how do we determine the row and column numbers of the square containing this point? This is pretty easy. Given that the squares are 30 pixels in each dimension, the row number is clickPoint.y / 30 and the column number is clickPoint.x / 30. There are a couple of things to note:

We naturally think of (x, y) and row/column—that is, first x, then y, and first row, then column. But notice that the row depends on y, not on x. And the column depends on x, not on y. So be careful here.
I wrote 30 in the expressions above because that's the square size. You will not write 30. You will use a constant.

Blackboard submission

Submit via Blackboard the zip file of a folder that contains the following two files: (1) Your Checkerboard.java, and (2) a screenshot of your checkerboard with a yellow square.