Killer Game Programming in Java

Managing the World

WorldDisplay manages:

• The moving tile floor, represented by a single GIF

• No-go areas on the floor

• Blocks occupying certain tiles

• Pickups occupying certain tiles

• Communication between the player and aliens sprites

The communication between the player and sprites in the game is rudimentary, mainly involving the transmission of position information and the number of pickups left. However, the coding technique of passing this information through the WorldDisplay is a useful one since it allows WorldDisplay to monitor and control the interactions between the sprites. WorldDisplay utilizes three main data structures:

• An obstacles[][] Boolean array specifying which tiles are no-go's or contain blocks

• A WorldItems object that stores details on blocks, pickups, and sprites in tile row order to make them easier to draw with the correct z-ordering

• A numPickups counter to record how many pickups are still left to be picked up

These are simply declared as variables in the class:

    private boolean obstacles[][];
    private WorldItems wItems;
    private int numPickups;

WorldDisplay's methods fall into five main groups, which I'll consider in detail in the following subsections:

• The loading of floor information, which describes where the tiles, rows, and columns are located on the floor

• The loading of world entity information, which gives the tile coordinates of the no-go areas, blocks, and pickups

• Pickup-related methods

• Player-related methods

• Drawing the world

Loading Floor Information

The floor image ...