Greenfoot Introduction (1)

Introduction To
Greenfoot
Part-1

kakihijau.googlepages.com

Disclaimer
 This document is intended to give a beginner an introductory
material for the Greenfoot system. Greenfoot is a software
framework made by Poul Henriksen and Michael Koelling at
University of Kent / Deakin University. More information can be
found at http://www.greenfoot.org

 This document is available „AS IS“ free of charge for personal use
and non-commercial redistribution. It may not be sold for profit or
included in other packages which are sold for profit without written
authorisation. This document is distributed in the hope that it will
be useful, but WITHOUT ANY WARRANTY; your use of the
document is at your sole risk. Reusing and modifying (part of) this
document is allowed, as long as you state explicitly that your work is
based on the original document produced by the copyright holder:
Eueung Mulyana. The author can be contacted via
eueung-[at]-yahoo.com (http://kakihijau.googlepages.com).

Introduction to Greenfoot 2
Eueung Mulyana | kakihijau.googlepages.com

Introduction
 „Greenfoot is a software tool designed to let beginners
get experience with object-oriented programming. It
supports development of graphical applications in the
Java™ Programming Language“
 Designed and implemented at the University of Kent and
Deakin University
 Copyright held by Poul Henriksen and Michael Koelling
 More information at http://www.greenfoot.org

 Part of the content of these slides is based on the
Greenfoot Tutorial made by Michael Koelling,
publicly accesible at the website


Outline
 Visual Interface
 Creating Objects
 Interaction with Objects
 Removing Objects
 Objects‘ Action
 Simulation „Run“
 Scenario plane
 Scenario turtleGraphics
 Scenario ants
 Scenario lunarlander


Visual Interface (scenario wombats)


Visual Interface
 Consists of 3 main parts

 The world
– The large canvas that covers the majority of the window
– Has a title e.g. WombatWorld
– The enviroment („the world“) where objects exist
 Class display
– Contains all Java classes involved in the scenario
– 3 groups: World, Actor and other classes
 Execution controls
– Controls the action of each object: the „Act“ button
– Controls simulation: „Run“, „Pause“, slider
– Resets the scenario


Creating Objects (1)

 (Left-)Click on the Wombat or Leaf class to make it
active

 To create and place an object into the world :
– Activate a class then shift+click somewhere in the World
– Right-click a class (e.g. Wombat class) to open the class context
menu, select the „New Wombat()“ item then click somewhere in
the World


Creating Objects (2)

Creating 3 objects and placing Class
them into the World context menu


Interaction with Objects (1)
 Methods of an object
can directly be invoked
 „A method is a single
action that an object
can perform“
 Right-click on one
object to show its
(object) context menu,
where you can select a
method to ask the
object to do
„something“

turnleft() move() Introduction to Greenfoot 9


 The world where the wombats live
(WombatWorld) is actually an
object, too
 But there may exist only one World
object at a time
 It functions as a container for Actor
objects (e.g. Wombat, Leaf etc.)

 Single method invocation is still
possible for the World object; just
right-click the title „WombatWorld“
and select a method from the menu



populate() randomLeaves()

 A method may have one or more parameters
 You will be requested to give value(s) of the parameter(s)
when you invoke such a method
 Try the method setDirection() from a Wombat object
or the method randomLeaves() from the
WombatWorld

 A method may also return one value (or reference to an
object) if it is invoked
 Try foundLeaf() or getLeavesEaten() from a Wombat
object


Removing Objects (1)
 An object can be removed by selecting item „Remove“
from the object context menu

 Clicking the „Reset“ button or creating a new World
object from the class context menu may remove all
objects; however it actually depends on the constructor
implementation of the World class  (*)


Removing Objects (2)


Objects‘ Action
 Each Actor object has a special method called act()
 Pressing the button „Act“ on the control panel means
asking Greenfoot to execute act() method for all objects
in the world

 An object acts by doing „whatever it wants to do“ e.g.:
– Wombats move forward, if they find a leaf in their path, they will
eat it
– Leaves do nothing
 The action depends actually on how act() method is
defined; that is, we can program object behaviors!!


Simulation „Run“
 A scenario can be run by clicking the „Run“ button
 This equivalent to clicking the „Act“ button over and over
again very quickly
 The slider next to the „Act“ and „Run“ buttons sets the
„running/simulation“ speed

 Make an experiment with scenario wombats
– Click „Reset“ if you have already some objects
– Select Populate() from the WombatWorld menu
– Click „Run“


Simulation „Run“

Running wombats scenario

Scenario plane (1)
 Choose „Open ...“ from the „Scenario“
menu and select the plane scenario
from the Greenfoot sample scenarios
 Press the „Compile all“ button, if
necessary
 Instantiate a Plane object and place
somewhere in the world
 Run the scenario by pressing „Run“
 Try to drag the ControlKnob object
and observe the result


Scenario plane (2)


Scenario plane (3)


Scenario turtleGraphics (1)
 Choose „Open ...“ from the „Scenario“ menu and select
the turtleGraphics scenario from the Greenfoot sample
scenarios
 Press the „Compile all“ button, if necessary
 Instantiate several turtle objects (CircleTurtle,
SquareTurtle, FlowerTurtle and SpiralTurtle) and
place somewhere in the world
 Observe the result


Scenario turtleGraphics (2)


Scenario ants (1)
the ants scenario from the Greenfoot sample scenarios
 By default (standard Greenfoot 1.3 distribution) you will
have several objects, which are actually formed together
as the World object is created; these objects are instances
of the class AntHill and Food; other objects will be
created „on-the-fly“
 Observe the result


Scenario ants (2)


Scenario lunarlander (1)
the lunarlander scenario from the Greenfoot sample
scenarios
 By default you will have a Lander object, which is
actually formed together as the World object is created
 Now you are ready to play the game; run the scenario by
pressing „Run“
 The rocket thrust can be controlled by pressing the
„down“ key on the keyboard


Scenario lunarlander (2)


Greenfoot Introduction (1)

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