Package greenfoot

Class World

java.lang.Object
greenfoot.World
public abstract class World extends 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.

See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    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

    Modifier and Type
    Method
    Description
    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).
    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).
    <A> List<A>
    getObjects(Class<A> cls)
    Get all the objects in the world, or all the objects of a particular class.
    <A> List<A>
    getObjectsAt(int x, int y, Class<A> 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(Collection<? extends Actor> objects)
    Remove a list of objects from the world.
    void
    repaint()
    Repaints the world.
    void
    setActOrder(Class... classes)
    Set the act order of objects in the world.
    final void
    setBackground(GreenfootImage image)
    Set a background image for the world.
    final void
    setBackground(String filename)
    Set a background image for the world from an image file.
    void
    setPaintOrder(Class... classes)
    Set the paint order of objects in the world.
    void
    showText(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 Details

    • 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 Details

    • 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

      public final void setBackground(String filename) throws 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:
      IllegalArgumentException - If the image can not be loaded.
      See Also:

    • 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 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.
      Returns:
      The color at the centre of the cell.
      Throws:
      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:

    • getWidth

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

    • getHeight

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

    • getCellSize

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

    • setPaintOrder

      public void setPaintOrder(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(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(Collection<? extends Actor> objects)
      Remove a list of objects from the world.
      Parameters:
      objects - A list of Actors to remove.

    • getObjects

      public <A> List<A> getObjects(Class<A> 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.

      Type Parameters:
      A - The type of objects to look for
      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 <A> List<A> getObjectsAt(int x, int y, Class<A> 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.

      Type Parameters:
      A - The type of objects to look for
      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).
      Returns:
      The list of objects whose graphical representation overlaps the centre of the cell.

    • showText

      public void showText(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