Game Development Reference
In-Depth Information
The World Class
The last class we have to discuss is the
World
class. It's a little longer, so we'll split it up.
Listing 9-15 shows the first part of the code.
Listing 9-15. Excerpt from World.java; Constants, Members, and Initialization
package
com.badlogic.androidgames.jumper;
import
java.util.ArrayList;
import
java.util.List;
import
java.util.Random;
import
com.badlogic.androidgames.framework.math.OverlapTester;
import
com.badlogic.androidgames.framework.math.Vector2;
public class World {
public interface
WorldListener {
public void
jump();
public void
highJump();
public void
hit();
public void
coin();
}
The first thing we define is an interface called
WorldListener
. What does it do? We need it to
solve a little MVC problem: when do we play sound effects? We could just add invocations of
Assets.playSound()
to the respective simulation classes, but that's not very clean. Instead, we'll
let a user of the
World
class register a
WorldListener
, which will be called when Bob jumps from
a platform, jumps from a spring, gets hit by a squirrel, or collects a coin. We will later register a
listener that plays back the proper sound effects for each of those events, keeping the simulation
classes clean from any direct dependencies on rendering and audio playback.
public static final float
WORLD
_
WIDTH
= 10;
public static final float
WORLD
_
HEIGHT
= 15 * 20;
public static final int
WORLD
_
STATE
_
RUNNING
= 0;
public static final int
WORLD
_
STATE
_
NEXT
_
LEVEL
= 1;
public static final int
WORLD
_
STATE
_
GAME
_
OVER
= 2;
public static final
Vector2
gravity
=
new
Vector2(0, -12);
Next, we define a couple of constants. The
WORLD_WIDTH
and
WORLD_HEIGHT
specify the extents
of our world horizontally and vertically. Remember that our view frustum will show a region
of 10×15 meters of our world. Given the constants defined here, our world will span 20 view
frustums or screens vertically. Again, that's a value we came up with by tuning. We'll get back
to it when we discuss how we generate a level. The world can also be in one of three states:
running, waiting for the next level to start, or the game-over state—when Bob falls too far
(outside of the view frustum). We also define our gravity acceleration vector as a constant here.
public final
Bob bob;
public final
List<Platform> platforms;
public final
List<Spring> springs;
public final
List<Squirrel> squirrels;
