TEACHING WITH
GREENFOOT
FOR TEACHERS OF ICS3U/4U
NOTE TO TEACHERS
• Everything you see here (these slides, code
samples, programs) are on your complimentary USB
drive.
AGENDA
• Intro – What is Greenfoot
• Greenfoot Basics –
(5 minutes)
(15 minutes)
• First look at Greenfoot – Creating a World and Actors
• Basic Concept Demo
• Important Elements of a good scenario
• Hands On Part 1
(20 minutes)
• Create your World, your Actor and create movement
• Collision Detection Tutorial
(10 minutes)
• Detect Objects colliding and triggering events
• Adding Sound
• Hands On Part 2
(remaining time…)
WHAT IS GREENFOOT?
• Greenfoot is:
• A simple yet useful Java IDE similar to BlueJ
• An easy-to-use 2D graphics engine
• An object based programming tool that allows for easy
demonstration and instruction of object oriented
programming through visual examples
• Easy to learn for any experienced Java programmer
WHY GREENFOOT?
• Java is a great academic language – it’s strict
structure and object oriented nature makes it ideal
for UCS3U/4U
• However, Java has an antiquated, tedious set of
graphics commands.
• Students quickly tire of text-only programming in
Java, and often struggle with Java’s built in
graphics
• Greenfoot provides an easier approach to creating
games and visual simulations
GETTING STARTED
• Greenfoot is available for Mac OSX, Windows and
Linux – (Java must be installed)
• Can easily be installed by your TST
• If it is not possible to have it installed, there is a
Windows-only “Greenfoot on a Stick” version that
can be run from a USB key – which is what we will
be working with today
PROS AND CONS
PROS
• Easy to start
programming games and
simulations complete with
2D graphics and sound
• Mouse support
• Extensible with the full
Java programming
language
• Makes for fun tasks and
assignments
• Effective way to teach
and demonstrate OOP
CONS
• Poor support for
text(although you can
use the System console)
• No 3D
• Ultimately limited to
games of moderate
complexity
• Must use included IDE
SOME ADDITIONAL BENEFITS
• Good for teaching Linked Lists – some Greenfoot
methods return a linked list of objects
• Useful for teaching inheritance – all sub-classes of
Actors can be further inherited from, leaving the
potential to create and use different super classes
to good effect
• Grade 11 students can usually have basic
functionality of some sort working within 1 period
• Module available for XBox360 Kinect module – It is
possible to use Greenfoot to program for body
motion capture! (although I haven’t tried…)
GREENFOOT RESOURCES
• The development staff of Greenfoot is active in
creating a plethora of resources on an on-going
basis, including:
• The Greenroom – Discussion forum and resources for
teachers, requires registration from teacher email address http://greenroom.greenfoot.org/
• Numerous online resources for learning Greenfoot http://www.greenfoot.org/doc
• Scenario (and code) sharing http://www.greenfoot.org/scenarios
• Discussion Forum for students –
http://www.greenfoot.org/topics
• And more…
FIRST LOOK AT GREENFOOT
I D E , A C T O R A N D WO R L D C R E A T I O N T U T O R I A L
ACTOR
• All objects that will move within the game world
should be sub-classes of Actor
• (It is possible to create non-Actor classes within
Greenfoot – useful for advanced projects)
• You can declare abstract sub-classes of Actor and
then create sub-sub-classes – useful for creating
related types of objects (I.e. different enemies in a
game)
WORLD
• Your program begins by you creating a sub-class of
World – defining your own game world
• Typically, the World will own the Actors.
• Includes a number of global variables – world size,
act() order, state of execution (is the game
currently running), etc.
PERSISTENT ACTORS
• In many programs, you will want to keep a
permanent reference to your Actors
• This is best accomplished by defining your Actors
within the constructor of your World class
• Your World can contain methods that allow Actors
to communicate
PERSISTENT ACTOR
DEMO
THE “MAIN” METHOD
• No main() method in Greenfoot
• The scenarios are run in “acts” where the act()
method of every class gets called once per frame
• Use your World (the class you created which inherits
from World, not World itself) as you would a main
method.
• You can add an act() method to your World (and
you should!)
BUILDING YOUR WORLD
• Some things that you should consider for your
World:
• setPaintOrder() – allows you to control which Actors are
displayed on top and which will appear behind
• setActOrder() – set the order in which classes’ act()
methods get called in each act.
• Store permanent references to Actors which you will need
to manage later
• Instance variables for your data and for program flow
YOUR FIRST GAME!
• Frogger Game!
• Little Frogger must cross the road without getting
smushed
• Example solutions (basic and advanced) on your
USB key
PROCESS
• Part 1 – Create the basic objects
• A World with a background image
• A little Frogger Actor that takes input from the keyboard
• Cars (or other Enemies) (Actors) that cross the road and
threaten to kill our poor frog!
• Part 2 – Add collision detection and associated
actions
• Part 3 – Finishing Touches, polish, as time allows
• Sounds
• Displaying Text (score, level, etc)
VARIOUS RESOURCES
• Greenfoot on a Stick – Greenfoot and all
associated Java libraries, runnable off of a USB key
• Paint.net – best free paint program I’ve been able
to find. Does transparency.
• Frogger! (my 3-4 hours of coding version)
• A few other scenarios