The little drawing system that I showed in class today is rather clunky, because it relies on two different types of objects -- TextLabel, and Drawable (and the various subclasses of Drawable), both of which use similar methods, but must be referenced separately.

Because of this, my code currently has two different arrays and two different logic loops for each of the three main operations: drawing, containment testing, and moving.

Your assignment is to get rid of this redundancy by having the drawing program use an interface named Movable. When you download and expand the zip file apr-21.zip, you will see a subfolder called movable. This folder is the package which contains the interface source file Movable.java, which has the following contents:

package movable;
import java.awt.*;

public interface Movable
{
   public void move(int dx, int dy);
   public void moveTo(int x, int y);
   public boolean contains(int x, int y);
   public void draw(Graphics g);
}

• Declare within both Drawable.java and TextLabel.java that they implement Movable. This will require you to do two things:
  • Add an import line at the top that says import movable.*;
  • Change the class declaration line by adding implements Movable to the end.

• Modify the applet class SceneApplet.java so that the two arrays Drawable drawables[] and TextLabel textLabels[] are replaced by a single array Movable movables[].

  After you do this, there should only be a single loop for drawing, a single loop for containment testing, and a single loop for moving the selected object (where now there are two separate loops for each of these operations).

• In your homework, don't use the picture of the car and popsicle-person and the two labels "Car" and "Fred". Instead, create your own scene with different graphical and textLable objects. Make your scene look very different from my example. Try to have fun with it and be creative!

• Also, for extra credit, you can try to do something interesting or original with the behavior of the drawing system, like using it to make a simple game, or an animation, or a simulation, or an interactive way of teaching something.