Killer Game Programming in Java

The Animation Framework

AlienTilesPanel is similar to JackPanel in Chapter 12; it uses an active rendering animation loop driven by Java 3D's timer. It displays an introductory image when the game starts, which doubles as a help screen during the course of play. While the help screen is being shown, the game pauses.

Managing the Game World

AlienTilesPanel creates the various game elements in createWorld():

    // globals game entities
    private WorldDisplay world;
    private PlayerSprite player;
    private AlienSprite aliens[];


    private void createWorld(ImagesLoader imsLoader)
    // create the world display, the player, and aliens
    {
      world = new WorldDisplay(imsLoader, this);

      player = new PlayerSprite(7,12, PWIDTH, PHEIGHT,
                      clipsLoader, imsLoader, world, this);
                      // sprite starts on tile (7,12)

      aliens = new AlienSprite[4];
      aliens[0] = new AlienAStarSprite(10, 11, PWIDTH, PHEIGHT,
                                                  imsLoader, world);
      aliens[1] = new AlienQuadSprite(6, 21, PWIDTH, PHEIGHT,
                                                  imsLoader, world);
      aliens[2] = new AlienQuadSprite(14, 20, PWIDTH, PHEIGHT,
                                                  imsLoader, world);
      aliens[3] = new AlienAStarSprite(34, 34, PWIDTH, PHEIGHT,
                                                  imsLoader, world);
       // use 2 AStar and 2 quad alien sprites
       // the 4th alien is placed at an illegal tile location (34,34)

      world.addSprites(player, aliens);
                       // tell the world about the sprites
    }  // end of createWorld()

Tile coordinates are passed to the sprites, rather than pixel locations in the JPanel. The two A* and two quad sprites are stored in an aliens[] array to make it easier to send messages ...