Outline:

Animation in Applets

• Examples

  • Animated Polygon
  • Animated Heart
  • Animated Magic Square

Graphical Objects + Animation = Sprites

• Examples:

  • Animated Heart 2
  • Happy Birthday animation
  • Hello World animated applet
  • All three

• Source:

  • basicletter.java
  • HelloBasic.java
  • source for Animated Heart 2 (Centergrav.java
  • shape.java (parent class for sprites in Centergrav)
  • square.java (extends shape, used in Centergrav)
  • circle.java (extends shape, also used in Centergrav)
  • Happy Birthday applet
  • centerletter.java used in the Happy Birthday applet

Methods of Animation

• Using the Timer Class

  • Example - Hello World with Timer (source, source code for myTimer)

  • Advantages:

    • simple to use
    • low CPU usage
    • synchronizeable

  • Disadvantages:

    • Incompatibility with web browsers- click for an example (source)

• Using Infinite Loop Animation

  • Example - Hello World with an Infinite loop and delay loop (source code)

  • Advantages:

    • Simple to understand
    • Compatible with anything

  • Disadvantages:

    • Doesn't allow simultaneous action
    • Speed varies vastly by computer and by other usage of CPU
    • CPU time completely used up - often freezes the computer completely.

• Using Runnable- the ultimate interface for animation

  • Example - Hello World implementing runnable (source)

  • Advantages:

    • Synchronizeable
    • Compatible
    • Lowest CPU usage

  • Disadvantages:

    • More "wordy"- more methods potentially involved
    • Less modular- explicit looping required
  • fallingletter.java source code

Flicker/speed- to repaint() or not to repaint()

• repainting

  • Examples:

    • Remember the Happy Birthday applet?
    • Long repainting Hello World applet (source)

  • Advantages to repainting:

    • Easy to do
      built in refreshing/undrawing of previous frame
    • Speed

  • Disadvantages of repainting

    • Flicker

  • Not repainting

    • Example: Long repainting Hello World applet using self-refrehsing letters (source, source for refreshing letters)
    • Race: Both at the same time (this will look virtually the same on a fast computer)

  • Advantages of not using repaint():

    • No flicker!

  • Disadvantages of not using repaint():

    • No built in redrawing- Example (source)
    • Therefore, you have to manually 'undraw' or overdraw each sprite. This can cause problems, as well: Example (source)
    • This can make it slow down slightly
    • Note: Since my example is dependant on fonts, if you have font smoothing turned on (in your display settings), the letters will leave "trails" as they move around.

Sprite Interaction

• Example: Hello World with interacting letters
• How to: source for applet
• source for letters (I'm not going to explain quite everything here)

Image Buffering

• Example: Hello World with interacting letters that uses image buffering
• How to: source for applet
• source for letters (similar to previous interacting letters)

Advantages of image buffering

• Sprite refreshing is unnecessary, so sprites can pass over each other with out undrawing over each other

Disadvantages of image buffering

• Creating the image can take more time than drawing on to the canvas, so animation goes slower

• Example: Hello World with Mandelbrot Set background (Source not shared)