Lab: GUIs, Factories, Screensavers

Problem Statement

It is often possible to create a number of shapes in a specific pattern algorithmically (i.e., using a loop and calculating the position, size, speed, direction, etc.). When combined with movement, this has the possibility of producing a very interesting effect, with very little effort. This is the basis of most screen savers.

Set Up

Accept the assignment and clone the repository. In Eclipse, you'll do this in the Git repository view. Import the project into Eclipse, as you have done a few times.

Screen Savers

For each of the screen savers below, you will create an appropriate child class of the Factory class and implement its createMovers that, given a Canvas and an integer as parameters, creates the given number of shapes within the given canvas in a specific pattern. The current Canvas class will work without modification because you will modify the paint and move methods of a separate class that extends Mover.

During the race

At the end of the race.

1. Racers in a Line

   Create a Racer class that is a derived class of Mover. Implement Racer's paint and move methods such that it draws itself like a rectangle and animates itself by moving straight across the screen from left to right at a random rate (i.e., each time move is called, its speed should be randomly set between 1 and 10). When it reaches the right side it should stop, like those racing games at the local carnival.

   Create a RacerFactory class that is a derived class of Factory. Implement the createMovers method to create the given number of Racers such that they are all the same size and are positioned in a line along the left side of the canvas and exactly fill its height. All Racers, no matter how many will be created, should start at the same center x-coordinate, 0, and have the same width, 20. The rest of their attributes should be set so that the rectangles are spread evenly across the edge of the canvas. For example, given 10 racers to create and a canvas that is 100 pixels tall, they should each be 10 pixels high and positioned with their center y-coordinates at 5, 15, 25, 35, 45, 55, 65, 75, 85, and 95, respectively.

   Add a button for the RacerFactory in the Main class.

   When run, it should appear like the rectangles are racing to the right side of the window.

   Note that you may have to do some minor adjustments to make the racers stretch the height of the canvas. The racers may not exactly be touching, but they'll appear to be to the user.


2. Walkers on a Diagonal

   Create a Walker class that draws itself like a rectangle and animates itself by moving at a constant rate in a random direction (i.e., each time move is called, its angle should be changed randomly). The speed of the Walker should be constant throughout its life.

   Create a WalkerFactory to create the given number of Walkers such that they are all the same size and are positioned in a line diagonally across the canvas with each touching the two adjacent rectangles at their corners. Their position and size should be set so that they are spread evenly across the canvas. For example, given 10 walkers to create and a canvas whose size is 100x200 pixels, you should create 10 walkers that are 10x20 pixels in size and centered at (5, 10), (15, 30), (25, 50), (35, 70), (45, 90), (55, 110), (65, 130), (75, 150), (85, 170), and (95, 190), respectively.

   The colors of the attractors should all be within one "class" of colors (e.g., all red, blues, or greens).

   Add a button for the WalkerFactory in the Main class.

   When run, it should appear like the rectangles are taking a random (i.e., drunken) walk.

Learning More!

1. Leaving a Trail

   Change the super class, Mover, such that it paints itself as a collection of connected line segments and animates itself by adding the current center of the shape to a collection of points (i.e., each time move is called, the center point is added to a collection). When drawn as a series of lines from the first point to the second point in the collection, from the second point to the third point, from the third point to the fourth point, and on and on until the last point in the collection, it will appear that the shape is leaving a trail behind marking where it has moved. To make the trail appear, each of the previous classes' paint and move methods will need to be modified to call their corresponding super method. Additionally, Mover will need to declare and initialize an instance variable that is a collection of all the past points.


2. Interesting Circles

   Implement an AttractorFactory class to create the given number of Attractors such that they are drawn as circles, all the same size, and are positioned in a circular pattern with each touching the one beside it (i.e., tangent to each other) like the marks on a clock (if those marks were circles). In this case, their position and size should be set so that they are spread evenly around the perimeter of a circle whose diameter is the minimum of the width and height of the canvas. Recall that the formula for computing the circumference, or perimeter, of a circle is 2 * Math.PI * radius. For example, given 4 attractors to create and a canvas whose size is 100x200 pixels, you should create 4 attractors that are 100x100 pixels in size and centered at approximately (100, 0), (150, 50), (100, 100), and (50, 50), respectively.

   The colors of the attractors should all be within one "class" of colors (e.g., all red, blues, or greens).

   Modify the Attractor such that it draws itself as a circle and animates itself in some "interesting" way. Options include orbiting, attracting towards the center as if by gravity, swarm effects, or simulating dynamical systems.

   Add a button for the AttractorFactory in the Main class.

Testing

There are no JUnit tests required for this application (but you could write them for some classes/functionality), but you should make sure you test your application thoroughly so that you know it's working correctly. How can you do that?

Common Issues

• Placement of movers: Test with only 4 movers without any movement--that makes the issues with placement clearer. You may also want to look at the Mover's methods too.
• The objects don't extend the length/width of the screen. Why does that happen? How can you address that issue? (The solution is relatively simple.)
• The trail doesn't appear. Use print statements to see if you can determine the issue.

Submission

This isn't graded, but you should push your code into the GitHub repository.