greenfoot
Class World

java.lang.Object
  extended by greenfoot.World

public abstract class World
extends java.lang.Object

World is the world that Actors live in. It is a two-dimensional grid of cells.

All Actor are associated with a World and can get access to the world object. The size of cells can be specified at world creation time, and is constant after creation. Simple scenarios may use large cells that entirely contain the representations of objects in a single cell. More elaborate scenarios may use smaller cells (down to single pixel size) to achieve fine-grained placement and smoother animation.

The world background can be decorated with drawings or images.

Version:
2.6
Author:
Poul Henriksen, Michael Kolling
See Also:
Actor

Constructor Summary
World(int worldWidth, int worldHeight, int cellSize)
          Construct a new world.
World(int worldWidth, int worldHeight, int cellSize, boolean bounded)
          Construct a new world.
 
Method Summary
 void act()
          Act method for world.
 void addObject(Actor object, int x, int y)
          Add an Actor to the world.
 GreenfootImage getBackground()
          Return the world's background image.
 int getCellSize()
          Return the size of a cell (in pixels).
 java.awt.Color getColorAt(int x, int y)
          Return the color at the centre of the cell.
 int getHeight()
          Return the height of the world (in number of cells).
 java.util.List getObjects(java.lang.Class cls)
          Get all the objects in the world, or all the objects of a particular class.
 java.util.List getObjectsAt(int x, int y, java.lang.Class cls)
          Return all objects at a given cell.
 int getWidth()
          Return the width of the world (in number of cells).
 int numberOfObjects()
          Get the number of actors currently in the world.
 void removeObject(Actor object)
          Remove an object from the world.
 void removeObjects(java.util.Collection objects)
          Remove a list of objects from the world.
 void repaint()
          Repaints the world.
 void setActOrder(java.lang.Class... classes)
          Set the act order of objects in the world.
 void setBackground(GreenfootImage image)
          Set a background image for the world.
 void setBackground(java.lang.String filename)
          Set a background image for the world from an image file.
 void setPaintOrder(java.lang.Class... classes)
          Set the paint order of objects in the world.
 void showText(java.lang.String text, int x, int y)
          Show some text centred at the given position in the world.
 void started()
          This method is called by the Greenfoot system when the execution has started.
 void stopped()
          This method is called by the Greenfoot system when the execution has stopped.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

World

public World(int worldWidth,
             int worldHeight,
             int cellSize)
Construct a new world. The size of the world (in number of cells) and the size of each cell (in pixels) must be specified.

Parameters:
worldWidth - The width of the world (in cells).
worldHeight - The height of the world (in cells).
cellSize - Size of a cell in pixels.

World

public World(int worldWidth,
             int worldHeight,
             int cellSize,
             boolean bounded)
Construct a new world. The size of the world (in number of cells) and the size of each cell (in pixels) must be specified. This constructor allows the option of creating an unbounded world, which actors can move outside the boundaries of.

Parameters:
worldWidth - The width of the world (in cells).
worldHeight - The height of the world (in cells).
cellSize - Size of a cell in pixels.
bounded - Should actors be restricted to the world boundary?
Method Detail

setBackground

public final void setBackground(GreenfootImage image)
Set a background image for the world. If the image size is larger than the world in pixels, it is clipped. If it is smaller than the world, it is tiled. A pattern showing the cells can easily be shown by setting a background image with a size equal to the cell size.

Parameters:
image - The image to be shown
See Also:
setBackground(String)

setBackground

public final void setBackground(java.lang.String filename)
                         throws java.lang.IllegalArgumentException
Set a background image for the world from an image file. Images of type 'jpeg', 'gif' and 'png' are supported. If the image size is larger than the world in pixels, it is clipped. A pattern showing the cells can easily be shown by setting a background image with a size equal to the cell size.

Parameters:
filename - The file holding the image to be shown
Throws:
java.lang.IllegalArgumentException - If the image can not be loaded.
See Also:
setBackground(GreenfootImage)

getBackground

public GreenfootImage getBackground()
Return the world's background image. The image may be used to draw onto the world's background.

Returns:
The background image

getColorAt

public java.awt.Color getColorAt(int x,
                                 int y)
Return the color at the centre of the cell. To paint a color, you need to get the background image for the world and paint on that.

Parameters:
x - The x coordinate of the cell.
y - The y coordinate of the cell.
Throws:
java.lang.IndexOutOfBoundsException - If the location is not within the world bounds. If there is no background image at the location it will return Color.WHITE.
See Also:
getBackground()

getWidth

public int getWidth()
Return the width of the world (in number of cells).


getHeight

public int getHeight()
Return the height of the world (in number of cells).


getCellSize

public int getCellSize()
Return the size of a cell (in pixels).


setPaintOrder

public void setPaintOrder(java.lang.Class... classes)
Set the paint order of objects in the world. Paint order is specified by class: objects of one class will always be painted on top of objects of some other class. The order of objects of the same class cannot be specified. Objects of classes listed first in the parameter list will appear on top of all objects of classes listed later.

Objects of a class not explicitly specified effectively inherit the paint order from their superclass.

Objects of classes not listed will appear below the objects whose classes have been specified.

Parameters:
classes - The classes in desired paint order

setActOrder

public void setActOrder(java.lang.Class... classes)
Set the act order of objects in the world. Act order is specified by class: objects of one class will always act before objects of some other class. The order of objects of the same class cannot be specified.

Objects of classes listed first in the parameter list will act before any objects of classes listed later.

Objects of a class not explicitly specified inherit the act order from their superclass.

Objects of classes not listed will act after all objects whose classes have been specified.

Parameters:
classes - The classes in desired act order

addObject

public void addObject(Actor object,
                      int x,
                      int y)
Add an Actor to the world.

Parameters:
object - The new object to add.
x - The x coordinate of the location where the object is added.
y - The y coordinate of the location where the object is added.

removeObject

public void removeObject(Actor object)
Remove an object from the world.

Parameters:
object - the object to remove

removeObjects

public void removeObjects(java.util.Collection objects)
Remove a list of objects from the world.

Parameters:
objects - A list of Actors to remove.

getObjects

public java.util.List getObjects(java.lang.Class cls)
Get all the objects in the world, or all the objects of a particular class.

If a class is specified as a parameter, only objects of that class (or its subclasses) will be returned.

Parameters:
cls - Class of objects to look for ('null' will find all objects).
Returns:
A list of objects.

numberOfObjects

public int numberOfObjects()
Get the number of actors currently in the world.

Returns:
The number of actors

repaint

public void repaint()
Repaints the world.


act

public void act()
Act method for world. The act method is called by the greenfoot framework at each action step in the environment. The world's act method is called before the act method of any objects in the world.

This method does nothing. It should be overridden in subclasses to implement an world's action.


started

public void started()
This method is called by the Greenfoot system when the execution has started. This method can be overridden to implement custom behaviour when the execution is started.

This default implementation is empty.


stopped

public void stopped()
This method is called by the Greenfoot system when the execution has stopped. This method can be overridden to implement custom behaviour when the execution is stopped.

This default implementation is empty.


getObjectsAt

public java.util.List getObjectsAt(int x,
                                   int y,
                                   java.lang.Class cls)
Return all objects at a given cell.

An object is defined to be at that cell if its graphical representation overlaps the center of the cell.

Parameters:
x - X-coordinate of the cell to be checked.
y - Y-coordinate of the cell to be checked.
cls - Class of objects to look return ('null' will return all objects).

showText

public void showText(java.lang.String text,
                     int x,
                     int y)
Show some text centred at the given position in the world. The text will be displayed in front of any actors. Any previous text shown at the same location will first be removed.

Parameters:
text - The text to display; can be null to show no text
x - X-coordinate of the text
y - Y-coordinate of the text


Greenfoot homepage