COMP 310 Spring 2010	Lec03: Ballworld design and animation

Quick UML primer:

• Boxes
  • Classes
    • Name, fields and methods
      • Concrete (regular type) vs abstract (italic type)
      • Chevrons sometimes used to denote interfaces.
      • Sometimes the "role" in which the class plays in the design will be also be noted.
    • Accessibility:  public (+), private (-), package (nothing)
  • Comments/Notes  (dog-eared)
• Lines:
  • Solid arrowheads -- generalization
    • solid line: inheritance
    • dotted line:implementation
  • Open arrowheads
    • solid line:  association ("has-a")  -- composition (with solid diamond end)  or aggregation (with open diamond end) or unspecified (no diamond end).   Java is always aggregation.
    • dotted line:   dependency ("instantiates", "uses", etc)

Ballworld design:

• ABall methods and fields
• New ball instantiation issues
• Bouncing off walls
  • The problem of discrete motion -- need to reset position back inside of animation canvas.
• Design patterns:
  • Union
  • Observer-observable
  • Template

Animation Techniques

• Timer for "flip-book" animation
• Observer-observable dispatching to notify multiple balls
• Paint process:
  1. Timer executes ActionListener
  2. ActionListener calls repaint on JPanel used as the canvas.
  3. Repaint event gets queued onto Java GUI system.
  4. Java GUI system calls paintComponent of canvas
  5. paintComponent calls updateAll on dispatcher (though not necessarily directly)
  6. Each ball gets updated (move and paint).

© 2010 by Stephen Wong