com.thekeirs.games.engine

Class GameObject

java.lang.Object

com.thekeirs.games.engine.GameObject

Direct Known Subclasses:

Sprite

public abstract class GameObject
extends java.lang.Object

Abstract superclass to represent a game object in the game world

This class is abstract so it is never used directly to create instances. The Sprite class is a subclass that also manages an image and is thus usable in a game.

Field Summary

Fields

Modifier and Type	Field and Description
android.graphics.RectF	boundingRect Tracks the upper left and lower right coordinates of a box that surrounds this object in world coordinates.
protected GameObjectManager	manager To be useful, every game object must register with the game object manager
java.lang.String	name The game object's name, used to look up an object in the game manager, or determine which object something has collided with.

Constructor Summary

Constructors

Constructor and Description
GameObject(java.lang.String name, android.graphics.RectF extent) Basic constructor.

Method Summary

Modifier and Type	Method and Description
boolean	contains(float x, float y) Checks if this game object's bounding box includes a given point.
abstract void	draw(android.graphics.Canvas c, float xScale, float yScale) Must be implemented by any subclasses to do the work of actually drawing the game object onto the screen.
long	getTimeOnScreen() Check how long a game object has been alive.
void	hop(float distance, float direction) Instantaneously move the game object a given distance in the given direction.
void	hopToward(float distance, float destx, float desty) Instantaneously hop the sprite a given distance in the direction of another point in world space.
boolean	intersects(GameObject other) Checks if this game object's bounding area intersects at all with another game object.
boolean	isFullyOffScreen() Returns true if this object is entirely outside the boundaries of the screen at the object's current location.
boolean	isFullyOnScreen() Returns true if this game object is entirely within the boundaries of the screen at the object's current location.
boolean	isInside(GameObject other) Checks if this game object's bounding rectangle is entirely inside of another object.
void	moveBy(float dx, float dy) Adjust the game object's position by a given dx and dy offset
void	onFling(float x, float y, float dx, float dy) Called when the user makes a fling motion on the screen, starting at a location inside this game object's bounding box.
void	onTouch(float x, float y) Called when the user taps the screen at a location inside this game object's bounding box.
boolean	removalRequested() Check if this game object is scheduled for removal
void	requestRemoval() Request that the game object manager remove this sprite after this update loop is complete.
void	setManager(GameObjectManager manager) Called by the GameObjectManager to be sure this game object knows who its manager is.
void	setMaxTimeOnScreen(int msec) Configure this game object to self-destruct after a given number of milliseconds on the screen.
void	update(int msec) Called once per screen refresh by the GameObjectManager to update the size, location, or other attributes of this game object as needed by the game's logic.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

name

public java.lang.String name

The game object's name, used to look up an object in the game manager, or determine which object something has collided with.

boundingRect

public android.graphics.RectF boundingRect

Tracks the upper left and lower right coordinates of a box that surrounds this object in world coordinates.

manager

protected GameObjectManager manager

To be useful, every game object must register with the game object manager

Constructor Detail

GameObject

public GameObject(java.lang.String name,
                  android.graphics.RectF extent)

Basic constructor.

Parameters:

name - name of this sprite (used to look it up later)

extent - initial area on the screen this sprite will occupy, in world units

Method Detail

setManager

public void setManager(GameObjectManager manager)

Called by the GameObjectManager to be sure this game object knows who its manager is. This method is called automatically - do not use.

Parameters:

manager - the current game object manager

update

public void update(int msec)

Called once per screen refresh by the GameObjectManager to update the size, location, or other attributes of this game object as needed by the game's logic.

If you are creating a subclass of GameObject or Sprite be sure to call super.update() in your update() method so that the object removal logic will work correctly.

Parameters:

msec - number of millseconds since the previous update call. Typically 16msec at 60Hz screen refresh.

onTouch

public void onTouch(float x,
                    float y)

Called when the user taps the screen at a location inside this game object's bounding box.

Parameters:

x - horizontal coordinate in world units

y - vertical coordinate in world units

onFling

public void onFling(float x,
                    float y,
                    float dx,
                    float dy)

Called when the user makes a fling motion on the screen, starting at a location inside this game object's bounding box.

Parameters:

x - horizontal coordinate in world units

y - vertical coordinate in world units

setMaxTimeOnScreen

public void setMaxTimeOnScreen(int msec)

Configure this game object to self-destruct after a given number of milliseconds on the screen.

When the game engine properly supports pausing/unpausing the game, this count should also "freeze" in place and resume counting again automatically.

Parameters:

msec - number of milliseconds until this game object requests automatic removal

getTimeOnScreen

public long getTimeOnScreen()

Check how long a game object has been alive.

Returns:

number of milliseconds this game object has been on screen/managed by the manager.

draw

public abstract void draw(android.graphics.Canvas c,
                          float xScale,
                          float yScale)

Must be implemented by any subclasses to do the work of actually drawing the game object onto the screen.

Parameters:

c - the Canvas object the game is currently being drawn onto

xScale - the horizontal scaling factor between world coordinates and screen coordinates

yScale - the vertical scaling factor between world coordinates and screen coordinates

contains

public boolean contains(float x,
                        float y)

Checks if this game object's bounding box includes a given point.

Parameters:

x - horizontal coordinate of the point to check, in world units

y - vertical coofdinate of the point to check, in world units

Returns:

true if the point is inside this object's bounding box

hop

public void hop(float distance,
                float direction)

Instantaneously move the game object a given distance in the given direction.

Parameters:

distance - distance to hop, in world units

direction - direction to hop in degrees counter-clockwise from the X axis

moveBy

public void moveBy(float dx,
                   float dy)

Adjust the game object's position by a given dx and dy offset

Parameters:

dx - horizontal offset in world coordinates

dy - vertical offset in world coordinates

hopToward

public void hopToward(float distance,
                      float destx,
                      float desty)

Instantaneously hop the sprite a given distance in the direction of another point in world space.

For instance, if you want bullets from a flying saucer to always fly towards your player's ship, this routine might be helpful.

Parameters:

distance - distance in world units to move the game object

destx - horizontal coordinate of the point to move towards

desty - vertical coordinate of the point to move towards

isInside

public final boolean isInside(GameObject other)

Checks if this game object's bounding rectangle is entirely inside of another object.

Parameters:

other - the game object to test if this object is inside of.

Returns:

true if this object is entirely inside other

intersects

public final boolean intersects(GameObject other)

Checks if this game object's bounding area intersects at all with another game object.

Parameters:

other - the game object to test if this object is touching

Returns:

true if this object intersects/touches other

isFullyOnScreen

public boolean isFullyOnScreen()

Returns true if this game object is entirely within the boundaries of the screen at the object's current location.

Returns:

true if the object is entirely on-screen

isFullyOffScreen

public boolean isFullyOffScreen()

Returns true if this object is entirely outside the boundaries of the screen at the object's current location.

Returns:

true if the object is entirely off-screen

requestRemoval

public final void requestRemoval()

Request that the game object manager remove this sprite after this update loop is complete.

removalRequested

public final boolean removalRequested()

Check if this game object is scheduled for removal

Returns:

true if this object will be removed.