Assignment 5a
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Drawing Shapes: Preparing the Infrastructure

What might we need to accomplish this?

First, we'll need a convenient place to draw our shapes. What can we draw shapes on? A Swing JPanel seems appropriate. So what if we derive our class from class JPanel -- how about a ShapesPanel?

Second, we should have some way of translating between the coordinate system of our ShapesPanel and the coordinate system required to display the data -- a kind of adapter class. Remember our CoordinateSystem class? That's its job.

Finally, we'll need some shapes to draw. Unfortunately, if we use the standard Java classes Point, Rectangle, etc., they're not really shapes, and they don't know how to draw themselves.

Note: I find it curious that the same folks who gave us this incredible Object-Oriented programming language didn't, in its original version, provide even a basic set of object-oriented shape classes! 
In the JSDK version 1.2 and beyond, they provide a set of classes for doing two dimensional drawing -- the 2D API -- but that's a topic for another course.

Since shapes have a set of common attributes and behavior, let's first create a class that captures that common stuff -- class Shape.

Then we'll at least have to create a class that represents a point -- class Point, derived from class Shape. Note that our class Point is not the same as java.awt.Point. Under some circumstances, you may need to explicitly qualify one or the other of these classes to ensure they don't conflict with each other.

Note: Do not change the name of your Point class!

Hint: Do not use wildcard importation, such as the following: 
import java.awt.*;

or:

import javax.swing.*;

Here's What To Do:

  1. Write a set of classes that satisfies the Shapes Specification. 

    Note that this specification is for the entire assignment, but in this part, we'll just focus on the following classes:

    • screen.ScreenCoordinate
    • shapes.Shape
    • shapes.Point
    • shapes.ShapesPanel
    • shapes.ShapesTest
    • world.Bounds
    • world.Coordinate
    • world.CoordinateSystem

    Note: This assignment uses a CoordinateSystem class that has been changed and enhanced from the version in the previous assignment.

    In this part, you should ignore the following classes:

    • shapes.FilledRectangle
    • shapes.Line
    • shapes.Rectangle

    Here's the order in which you probably should implement the classes you need for this part of the assignment:

    1. Coordinate and ScreenCoordinate
    2. Bounds
    3. CoordinateSystem
    4. Shape
    5. Point
    6. ShapesPanel
    7. ShapesTest

    (You can implement them in any order you like, but since the classes have interdependencies, you'll probably have trouble if you deviate from the above order too much.)

    I encourage you to implement small pieces of each class, get something that compiles and (to some extent) runs, and then iterate a number of times over them to produce the final result. It's always a good idea to implement a small piece, get it working, and then add to it progressively. Don't try to add everything at once, or you'll likely get stuck and become quite frustrated!

    Note: I have intentionally organized these classes into three packages: shapes, world, and screen. It is important to keep these classes in these specified packages. 
    As before, you may not change the specification, except to add main() methods for testing purposes.

  2. Use These Classes to Produce Equivalent Results to the Previous Assignment

    My solution produced the following results for the set of points specified in assignment 4:

  3. Finally, To Ensure That You Did Things Correctly:

    Change the set of points to be displayed by the ShapesTest class to:

    To obtain this source code, you can copy and paste the above into your Java IDE, or do a 'Save Link/Target as...' on this link.

    After you've made the changes, see what your program displays!  

    You shouldn't have to make any other changes to the classes you wrote for this part of the assignment other than changing the m_shapes array, above.  If you do have to make additional changes to make this last part work correctly, you need to go back and ensure that the earlier parts of this assignment still work.

    If your program doesn't show anything reasonable, or if it doesn't display all the points in the ShapesPanel, or if it doesn't scale properly, then go back and fix the problems, and make sure that the program still works with the original set of points.

 

This page was last modified on 02 October, 2007