Bowden_BL_T_2014
Contents
1. fe JKarelRobot lolx File Edit Help Walls Around Cursor gt Cursor Karel s Initial Situation North lt lt gt Place At Cursor Pues ee Les Le rome ee O Corner Beepers ol Beepers In Bag 0 4 DO ip E G A GS UE le Avenues 12 Ta TA fe MGs iF Figure 2 1 Screenshot for JKarel 31 robots can sense and pick up 8 31 The students program the robots to move and interact with the environment by picking up beepers and avoiding walls 8 31 The student writes the entire program for the robot with each step in the program is performed during each tick of the global clock 31 One of the drawbacks of Karel is that there is not much flexibility to the students since students will only ever be writing behaviors for the robots in the 2D grid world This limits its usefulness as a long term learning tool since Karel can only be used to teach basic logic and object oriented concepts to students and students would generally quickly outgrow Karel Brian L Bowden Chapter 2 Related Work 9 create new variable backwards and jump create new method Do together Ee IceSkater Figure 2 2 Screenshot for Alice IDE 2 2 Alice Alice is a 3D interactive animation program released in 1999 2 Alice differs from Karel in that it allows2. finite state machines and the case for programming as part of general education in JEEE Symposia on Human Centric Comput Language and Environments 2001 Stresa Italy 2001 Brian Dorn and Dead Sanders Using Jeroo to Introduce Object Oriented Program ming in ASEE IEEE Frontiers in Education Conference 2003 Boulder Colorado USA 2003 Timo Rongas et al Classification of Tools for Use in Introductory Programming Courses Lappeenranta University of Technology Finland Duane Buck and David Stucki JKarelRobot A Case Study in Supporting Levels of Cognitive Development in the Computer Science Curriculum in SIGCSE Symposium 2001 Charlotte North Carolina USA 2001 Sally Fincher et al Comparing Alice Greenfoot amp Scratch in SIGCSE Symposium 2010 Milwaukee Wisconsin USA 2010 Ian Utting et al Alice Greenfoot and Scratch A Discussion ACM Trans Comput Educ Volume 10 4 11 pages 2010
3. 28 a Shape object as one of its fields referred to as the delegate Rather than have the DelegatingShape object itself handle bounds checking appearance and collision detection it instead lets the delegate handle these By doing this a delegating shape object can alter the way it behaves by simple changing the delegate shape inside the object Actors use an ImageShape as their delegate which is an extension to the RectangleShape class with an image used for the appearance of the shape rather than a fill color This also means that actor s use the RectangleShape s bounds and fixtures when it comes to collision detection When an actor is created Sofia will automatically try to find an image with the same name as the actor in the res drawable folder and assign that as the ImageShape s image This eliminates the need for users to explicitly search for an image in the code and can allow Sofia to perform this step for them however the user still has the option of explicitly setting the image A cache is used to help speed up looking up images when multiple actors of the same class are created by using either the actor s class name or a String as the key Actors are also given a bounds which is the bounding box used for collision detection and also determines how large the actor is Actors have a flag to determine if the bounds should be scaled to the grids in the world If the flag is set to true which is generally the case fo
4. 5 6 Ants vs Some Bees Screenshot Students can extend the Ant class to create new Ants that can perform different roles such as generating extra resources or dealing damage in an area around itself 5 4 1 Actors and Greenfoot on Android This case study emphasizes the actor of Sofia Micro All the game entities see Figure 5 5 are actors in this game with all of their behaviors written using the act method This program demonstrates that Sofia Micro can support a complete Greenfoot style program on Android The projectiles could be rewritten to move using the physics engine however a drawback of using both the act method and the physics engine is that they do not move in sync The game is still largely event driven since students select and place the ants within the world Brian L Bowden Chapter 5 Case Studies handler within the Colony java class for adding new ants to the World public void onTouchDown int x int y Ant ant newActor0fSelectedType if ant getFoodCost lt getFood consumeFood ant getFoodCost add ant x y 46 5 4 2 Greenfoot Style Programs on Android of Familar Android Apps Much like the Irritated Avians case study Ants vs Some Bees demonstrates that Sofia Micro solves the two issues in much the same way Students can easily create a version of a popular game they would be familiar with making Android more accessible to introductory students There is more variat
5. L Bowden Chapter 2 Related Work 11 26 BlueJ also uses an UML style layout to display the class structure of the project and allows students to directly interact with classes or objects 26 27 Once a student creates the object it is shown visually to help students grasp abstract object oriented concepts and the student can interact with the object to invoke any of its public methods 26 27 BlueJ also allows students to inspect objects to see the current values for their fields which allows for experimentation as the student can call the public methods then see the results of the method call 26 The downside to BlueJ is that in order to achieve its goal of simplicity it has to sacrifice many of the tools found in a professional environment which makes it only suitable as a learning tool 27 2 4 Jeroo and Kara Jeroo and Kara are two microworlds based heavily on Karel Jeroo focuses on object orented concepts using a kangaroo like animal called a Jeroo that trys to avoid traps on an island and pick up flowers 5 Jeroo uses an IDE where students can edit the code and see which line of code is being executed at a time 29 Students can also change the speed at which the simulation is running or even run it one step at a time 29 Kara is a ladybug that avoids tree stumps moves mushrooms and picks up or places clover leaves 28 Kara focuses on the idea of Finite State Machines since the authors believes that FSM are easy for
6. The amount of code that needs to be written is also fairly minimal numbering roughly around 70 80 lines of code excluding comments and whitespace The physics engine handles most of the trickier logic for this application so students can instead focus on writing the dpad handlers and setting up the actors for the world Asteroids also shows that students can create diverse applications to increase the life span of Sofia Micro as a learning tool 5 3 Irritated Avians This case study is a simplified implementation of the Angry Birds game renamed Irritated Avians The goal of the game is to the launch the red bird at the green pigs in order to remove them from the world To play the user will drag the red bird and release at the desired angle and distance which will propel the bird forward and if it collides with one of the green pigs then the pig will be removed from the world This game was originally written using the base Sofia framework by 14 and was modified to fit Sofia Micro In the Brian L Bowden Chapter 5 Case Studies 42 Figure 5 4 Irritated Avians Screenshot Sofia Micro version the birds and pigs are now actors however they still use the physics engine to determine movement and collisions The ground and the ovals the bird leaves behind when fired were left as shapes since they have no behavior in this scenario 5 3 1 Event Driven Programming with Physics Like the Asteroids case study Irritated Avians als
7. any motion events and sends them to a helper method This method checks to ensure that the mo tion event is within the bounds of the dpad and calculates if the touch was in the center of the dpad or which one of the 8 quadrants of the dpad the touch occurred Touching the center or one of the four cardinal directions converts the touch event into a single key event for example touching the top portion of the dpad will convert the touch event into a KEYCODE_DPAD_UP key event Touching one of the corner will convert the touch event into two key events for example touching the top right corner will convert it into a KEY CODE_DPAD_UP and KEYCODE_DPAD_RIGHT key event These key events are then Brian L Bowden Chapter 4 Design amp Implementation 35 redispatched where they are handled and buffered by the WorldView If an actor or world has one of the directional pad methods then the DpadDispatcher class will dis patch the dpad events to the class If an actor con tains one of the dpad diagonal directions then the event is dispatched to that method if not then it is dispatched to the two corresponding cardinal direc tions ie northwest would be dispatched to north and Figure 4 4 Directional Pad west However the KeyEvent class does not have a constant for the diagonal directions so to ensure they are properly dispatched a bitmask is used where the two directions are com bined into a single int using bit shifts and AND
8. screen Brian L Bowden Chapter 3 Sofia Micro Features 24 For these handlers students can also specify additional arguments for the methods These handlers can take two floats or two ints one for the x coordinate and one for the y coordinate or a Point object which contains the respective x and y coordinate Students can also make use of Sofia s unique event dispatch model to help simplify some of the code they need to write For example in the Asteroids case study rather than having the following in the act method Set lt Ship gt ships getIntersecting0bjects Ship class if ships isEmpty for Ship ship ships ship remove Students can instead write public void onCollisionWith Ship ship ship remove remove The latter helps emphasize an event driven model since it is only called when there is actually a collision as opposed to constantly checking if a collision has occurred In terms of writing handlers for typical events such as touch or key events students just need to write the appropriate handlers in their actor or world Any captured events are stored in a buffer and Sofia Micro will automatically dispatch any buffered events to classes with handlers by using Reflection before the act method is called for the world and actors respectively To help facilitate students writing event driven programs Sofia Micro also supports the Brian L Bowden Chapter 3 Sofia Micr
9. 6 Brian L Bowden Chapter 5 Case Studies public void myProgram clearRows public void clearRows while seesWater AHEAD isClearBelow if clearRow if isClearBelow turnAround else if this seesWater down moveToNextRow 37 The other actors in the jeroo package ie the flowers and nets are just regular actors While they do not have any defined behavior by default it does demonstrate that a jeroo Figure 5 1 Jeroo in Sofia Micro Brian L Bowden Chapter 5 Case Studies 38 world can support both actors and programmable actors in the same world Jeroo also demonstrates that Sofia Micro can recreate previous microworlds in an Android environment which allows for instructors and students to use them in a strictly Greenfoot style or Karel style if they so choose 5 1 2 Simple Microworlds on Android Jeroo shows that it addresses both issues of the problem statement Students can create unique and diverse Greenfoot style or Karel style microworlds to help keep the tool inter esting and give it some longevity Also given the ease with which they can create these environments it shows that Sofia Micro can help bring Android to students in an simpler context 5 2 Asteroids In this program the user controls a ship that must avoid the asteroids on the screen and shoot them to destroy them If a bullet collides with an asteroid then both are removed from t
10. Sofia Micro An Android Based Pedagogical Microworld Framework Brian L Bowden Thesis submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science in Computer Science and Applications Stephen Edwards Chair Eli Tilevich Manuel Perez May 2 2014 Blacksburg Virginia Keywords Android Microworld Sofia event driven CS 1 Java programming assignment introductory programming Copyright 2014 Brian L Bowden Sofia Micro An Android Based Pedagogical Microworld Framework Brian L Bowden ABSTRACT Microworlds are visual 2D grid based worlds with programmable actors that help ease stu dents into programming Microworlds have been used as a pedagogical tool for teaching students to program in an object oriented paradigm for several years now With the pop ularity of Android smart phones creating a pedagogical microworld for Android can help students learn not just Java OO and event driven concepts but also learn to use the Android framework to create concrete real world applications This thesis presents Sofia Micro an Android based pedagogical microworld framework that not only allows Greenfoot style mi croworld programs to run on Android but also adds additional functionalities to microworlds that have not been previously explored such as built in shape and physics support event driven programming in a mic
11. TErOIdS e e de dota its e ARAS AE 38 5 2 1 Event Driven Programming using the Dpad Controller and Simple Presi eat sess eras ca A berated a a Ee he Seg E E T ath a 40 5 2 2 Easily Creating Simple Physics Based Games 41 5 3 a AA A ere a EA ck elt OE ok ot ht 41 5 3 1 Event Driven Programming with Physics 42 5 3 2 Creating Simple Versions of Familiar Android Apps 43 5 4 Ants vs Some Bees Sik AA Oh a OE a A ee da 44 5 4 1 Actors and Greenfoot on Android 45 5 4 2 Greenfoot Style Programs on Android of Familar Android Apps 46 6 Conclusion 47 6 1 Contributions ta A AA A ee ea 47 6 2 Future Work siss g an a ee E Ok ema a Bota ed 48 References 49 2 1 2 2 2 3 2 4 2 5 2 6 2 7 3 1 3 2 3 3 4 1 4 2 4 3 4 4 5 1 5 2 5 3 5 4 5 9 5 6 List of Figures ocreerishot for JKarel s fed pista apie A ALE Ged 8 Screenshot for Alice IDE ent a AER AA 9 BlueJ Class Laygut sui bed ont kek ohn ee Ses Se a A A 10 Kara Sample PTOgTaNN e si loa e Soy ie bE yal ara ls Pdo a A Eara a thd 12 Greenfoot Wombats example a 00000 eee 13 Scratch Sample Program A E A e A eed 14 Daisy the Dinosaur App si RAE oe eS a 15 Actor UML Diagram aoaaa a 18 World UML aera 2d O Soe ewe sr ri 18 Screenshot of Physics Games on Google Play Store 20 Sota Micro UML Diagram oho sos a NA ok We Bk ee ea 26 Sota Micro Menu a a oes aah as ks Jae ok acd ae HU Si
12. actor from the beginning and think about solving their problem in a more global sense and think about their logic in a more abstraction oriented perspective The other type of actor is the cellular automata style actor such as the ones used in Greenfoot For these types of actors students write what each actor will do at each step of the world clock with the actor reacting to their immediate surroundings and then moving 17 Brian L Bowden Chapter 3 Sofia Micro Features 18 Figure 3 1 Actor UML Diagram Figure 3 2 World UML Diagram removing itself or another actor changing direction etc This follows an approach similar to how a greedy algorithm works where the actor makes the best local decision in order to try to solve a global problem This style of writing actors is less restrictive than the programmable actor style since students just need to focus on writing how an actor should respond at each individual step rather than how they should respond over the entire program These types of actors can usually be identified by an overridden method that appears in every actor and world in the case of Greenfoot and Sofia Micro this is the act method Sofia Micro employs both types of actors and worlds that are commonly used for these microworlds namely actors and programmable actors and worlds and programmable worlds Like in the Greenfoot model each actor has an act method that is called during each tick of the g
13. al Teaching Objects first in Introductory Computer Science in SIGCSE 2003 Reno Nevada USA 2003 Kim Bruce et al Java An Eventful Approach Upper Saddle River New Jersey USA 2004 Kim Bruce et al Event Driven Programming Facilitates Learning Standard Program ming Concepts in OOPSLA 2004 Vancouver British Columbia Canada 2004 Kim Bruce et al Event Driven Programming can be Simple Enough for CS 1 in ITiCSE 2001 New York City New York USA 2001 Kim Bruce et al A library to support a graphics based object first approach to CS 1 in SIGCSE 2001 New York City New York USA 2001 Michael K lling 2010 November The greenfoot programming environment ACM Trans Comput Educ Volume 10 4 21 pages Available http dl acm org citation cfm id 1868361 Accessed December 26 2013 Poul Henriksen and Michael K lling greenfoot Combining Object Visualisation With Interaction in OOPSLA 2004 New York NY USA 2004 Michael K lling et al 2003 December The BlueJ system and its pedagogy Journal of Comput Science Educ Special Issue on Learning and Teaching Object Technology Volume 13 4 Brian L Bowden Chapter 6 Conclusion 51 27 28 29 30 31 32 33 Michael K lling and John Rosenberg 2010 November Guidelines for Teaching Object Orientation with Java in ITMCSE 2001 Canterbury England UK 2001 Werner Hartman et al Kara
14. ayList never needed to be resized or in the worst case had to be resized once Since the Brian L Bowden Chapter 4 Design amp Implementation 33 ArrayList does not need to go out to the heap every time to add an item to the buffer it was the data structure that was used Another design consideration was the way the events were stored in the buffer One problem is that the action for motion events and key code for key events are static as in there is only a single copy stored across all events When buffering and then dispatching the events the action would always be the action of the last motion event stored and likewise for the key event To fix this issue rather than just buffering the event itself a wrapper class was created that would store both the event and the action or key code at the time it was buffered This wrapper class is created every time an event is fired and then stored in the corresponding buffer One issue that arose with motion events is that the x and y value stored in the motion event are in pixel coordinates however this is not suitable for a grid based microworld since actors are generally addressed by their grid x and y coordinate To address this issue the x and y values in the motion event are adjusted so that the pixel locations are converted to grid cell coordinates and offset so pixel coordinates to the left of the origin 0 0 are considered negative These adjusted x and y val
15. c static or kinematic Shapes are by default static which means it has zero velocity and infinite mass and can only be manually moved by the user Kinematic shapes also have infinite mass but they can be given a velocity Static and kinematic bodies will not interact with each other or themselves On the other hand dynamic shapes are subject to all types of physics interactions including velocity mass forces torques and impulses 3 Dynamic shapes also can interact with all three types of shapes and use the shape s built in fixtures to simulate any physics Sofia also supports a shape filter where a user can chain together multiple filters onto the same call There is support for finding actors in the ShapeView and WorldView that Brian L Bowden Chapter 4 Design amp Implementation 31 Figure 4 3 Shape UML Diagram Note not a complete UML diagram applies the necessary filters to simplify some commonly used collision detection or search queries that are typically done For example if a user wanted to find all the actors within a circle at coordinate x y they could use getShapesInRange x y r Actor class Which is merely a shortcut for return getShapes withClass Actor class locatedWithin new PointF x y r all Brian L Bowden Chapter 4 Design amp Implementation 32 Sofia also provides animation support for shapes as well Users can chain together different animations such as fading in the shap
16. ck eta a a 27 Shap UME Diagram a Ta sid pa AA A ok od Se oa 31 Directi nal Pad 21 a ko Po A A A A E A E Ee 35 Jeroom Sofa MIO aTi argue en ea Seah a att ad Sa ae ON inden ee aed 37 Asteroids UML Diagram ESA E E he ose ee 39 Asteroids Layout aios oS is e ic iO AO 39 Irritated Avians Screenshot seoc y pa A A A 42 Ants vs Some Bees UML Diagram 44 Ants vs Some Bees Screenshot 00 000 e e 45 vi Chapter 1 Introduction 1 1 Microworlds Many universities have been using the objects first strategy in teaching students program ming for introductory courses for several years now 19 This approach teaches students to focus on object oriented concepts from the beginning when first learning to program such as inheritance objects and polymorphism 19 However students have to overcome several hurdles when initially learning programming To help students overcome some of these difficulties microworlds have been developed as a pedagogical tool to ease students into programming Microworlds are visual 2D grid based environments with objects that have programmable behavior and their goal is to help students think in an algorithmic manner Microworlds typically start students off with small programs that have simple objects with well defined behaviors so students can focus on writing the logic of the object s behaviors in the worlds This helps emphasize teaching students to think in a step by st
17. d new Bullet 50 int getRotation getGridX getGridY Asteroids also demonstrates the event dispatch strengths of the Sofia framework since detecting collisions happens automatically now with the onCollisionWith methods so students can instead focus more on what happens when a collision occurs public void onCollisionWith Ship ship ship remove remove Secondly it emphasizes the use of the physics engine in realistically moving actors so that students do not need to worry as much about moving objects or bouncing Asteroids off each other when they collide This was accomplished by changing the MovingActor class which is the class all the actors in this scenario extend from to be a dynamic shape Movement for the actors is handled in the constructor method by setting its linear velocity Brian L Bowden Chapter 5 Case Studies 41 to be speed cos speed sin While this may not change a lot in terms of how the game is played it does make the game feel more like a physics based game rather than merely emulating one Finally this case study demonstrates how the dpad works for Sofia and that users can use it as a controller for one or more actors in their microworld 5 2 2 Easily Creating Simple Physics Based Games Like the jeroo Asteroids shows that it addresses both of the main issues in the problem statement Asteroids demonstrates how easy it is for someone to write a very simple game that works
18. e or to allow for on screen buttons to also accompany the dpad 10 11 12 Bibliography Android Developers Developer Support Android Developers Online Available http developer android com guide index htm1l Accessed April 14 2014 Alice Alice 1999 2014 Online Available http www alice org index php Ac cessed April 14 2014 Box2D Documentation Box2D v2 2 0 User Manual Online Available http www box2d org manual html Accessed April 9 2014 Letzte nderung Learn Programming with Kara Swiss Education Computer Science Learn Programming with Kara 2014 Onlinej Available http www swisseduc ch compscience karatojava kara Accessed April 8 2014 Brian Dorn and Dead Sanders Jeroo Jeroo 2008 Online Available http home cc gatech edu dorn 38 Accessed April 8 2014 Scratch Scratch Imagine Program Share 2013 Online Available http scratch mit edu Accessed March 20 2014 Greenfoot Greenfoot About Greenfoot Online Available http www greenfoot org door Accessed April 20 2014 Karel Karel J Robot 1999 2014 Online Available http www cafepress com kareljrobot Accessed April 17 2014 Cato s Hike Kato s Hike 2012 Online Available hwahba com catoshike Ac cessed April 17 2014 Daisy the Dinosaur Daisy the Dinosaur 2012 Online Available http www daisythedin
19. e over 1 second while changing the color 4 3 Event Dispatch The event dispatch is accomplished in the WorldView class by using a double buffer system Events are buffered in an ArrayList whenever they are caught in the WorldView During the run loop for the World before the act is called for the World all the events in the buffer are dispatched to the World The same is done for each actor before that actor s act method is invoked This allows for motion and key events to be handled before the world or actor s behavior is performed While events are being dispatched to the World and each actor the second buffer will catch any events that may be fired during that time since dispatching events is not handled instantaneously Once the World s and actor s act methods have been performed then the buffers are swapped and the second buffer will be used on the next iteration of the run loop and so on During implementation of the double buffer a LinkedList was also considered for the double buffer since the ArrayList has to worry about potentially expanding the internal array if the number of buffered events got too large whereas the LinkedList does not have to worry about such a consideration On the other hand the LinkedList has to go out to the heap every time a LinkedList node is created which can be relatively expensive whereas the ArrayList just has an array of references that do not need to be recreated In practice the Arr
20. ed commands typically found in an IDE to reduce complexity for students 25 The GUI also allows students to interact directly with classes and objects by right clicking on them 25 Users can create new Actors by right clicking on the Actor in the Actor menu see Figure 2 5 and users can also inspect the state of the actor by right clicking and hitting inspect from the actor s menu 25 In this way Greenfoot helps make object oriented more concrete by allowing users to create and see the actors they write Greenfoot s strength stems from the fact that it easily allows students and instructors to write custom scenarios This avoids the drawback of Karel and the Karel like microworlds Brian L Bowden Chapter 2 Related Work 14 SCRATCH Fev Edity Tps m Dance Party Eu B Scripts Costumes Sounds gt J Motion f Events J Looks J souna f sensing f operators J More Blocks Oo ov 2 S BS 3 8 x 240 y 180 Sprites New sprite Stage i Cassy Da 2 backdrops New backdrop a an a Figure 2 6 Scratch Sample Program 18 since there is much flexibility in what students can write However like BlueJ the IDE does not contain many of the tools typically found in an IDE 2 6 Scratch Scratch created by the Lifelong Kindergarten Group at MIT is an online tool for novice pro grammers to learn computer science concepts Scratch also emphasizes the no syntax error philosophy
21. ep methodology and focus on correctly writing out their logic Another issue is that students learning programming struggle with the fact that many Brian L Bowden Chapter 1 Introduction 2 concepts in programming are too abstract The idea of the state of variables as well as basic data structures prove to be a challenge for students who have a hard time conceptualizing what is occurring in a program 30 Microworlds aim to make programming more concrete and interesting by visually representing the state so students can see what is happening in their program 30 Since students can see what is happening in their program they can easily detect when a given object does not act correctly and can check their logic to see where the problem occurs 30 Visualization also helps prevent the common habit of trial and error programming that introductory students tend to exhibit where they just try changing random segments of code to fix a bug without thinking through the logic clearly 30 1 2 Sofia Android a framework for mobile devices that uses Java and is built on the Linux kernel has recently emerged as a popular framework for both teaching and software development 14 Android has shown to be an effective motivator for students due to its ability to allow programmers create more concrete and ultimately interesting applications However learning Android has proved to be difficult for introductory programmers because the tools were des
22. fia Micro follows the Greenfoot style more as it uses Java classes and syntax since we want Sofia Micro to be a natural transition to writing mobile applications There have been a number of different microworlds created since Karel s inception in 1981 Different microworlds have different maturity requirements with Alice and Scratch being suitable for middle school aged students and Greenfoot and Karel being suited for high school and even collegiate level students 25 33 Since Sofia Micro is based on Green foot and Karel and also uses the Android framework we feel it would be best suited for high school and collegiate level students 2 1 Karel Karel was the first microworld released in 1981 and started the idea of using 2D grid based worlds with programmable actors to help teach students object oriented concepts The 2D grid used to represent the world has the origin in the bottom left corner and starting at 1 1 to allow for using coordinates similar to the top right quadrant in the Cartesian plane 8 31 In this world the vertical coordinates are called streets and the horizontal coordinates are called avenues 8 31 Actors in this world are represented as robots which the students write behaviors for walls that the robot can not move through which are placed by the user and also on the bottom and left edge of the world and black dots called beepers that the Brian L Bowden Chapter 2 Related Work 8
23. have some experience with programming 1 3 Problem Statement This thesis will address two main issues First we want to bring microworlds to Android We would like to be able to use Android as a learning tool for introductory students because it can be a great motivator due to students being able to create real world applications that others can see Android emphasizes event driven programming which has shown to be an effective programming paradigm for teaching students by Kim Bruce et al in several of their Brian L Bowden Chapter 1 Introduction 4 works 20 21 22 23 However Android is too complex for most beginner students since it retains many of the drawbacks of learning Java plus the framework Second microworlds do not retain their usefulness as a teaching tool throughout an entire CS 1 course This is largely because students not only quickly master the tools given to them but the problems given to students are only useful for solving early beginner problems 30 More recent microworld frameworks such as Greenfoot have allowed students and instructors to create their own scenarios within the framework 7 24 We would like for students to be able to create varied and interesting applications within the microworld that would not only be engaging for students but would also be complex enough to where the students would not quickly outgrow the framework and would last a full CS 1 course This framework would also ideally all
24. he world Likewise if the ship collides with an asteroid then both are removed and the player has to restart the app to keep playing The user controls the ship using the dpad and tapping the screen Touching the up section of the dpad will move the ship forward in the direction it is facing while touching the down section will slow the ship down Touching the left or right areas will turn the ship in the corresponding direction and tapping the screen will cause the ship to fire bullets The ship does not have any of the diagonal dpad methods Brian L Bowden Chapter 5 Case Studies 39 Figure 5 3 Asteroids Layout so the dpad dispatcher will dispatch any diagonal directions into the corresponding cardinal directions Brian L Bowden Chapter 5 Case Studies 40 5 2 1 Event Driven Programming using the Dpad Controller and Simple Physics This case study emphasizes a few different aspects of Sofia Micro It first emphasizes the event driven nature of both Sofia Micro and Android applications Students would need to write the dpad handlers for the ship to control the ship s movement The amount of code students need to write for the ship s handlers is a single line per handler public void dpadNorthIsDown setSpeed getSpeedO 1 gt public void dpadSouthIsDown setSpeed getSpeed 1 public void dpadEastIsDown turn 5 public void dpadWestIsDown turn 5 public void onScreenTouchDown getWorld ad
25. hysics engine This gives microworlds the added fea tures of simulated gravity collision detection use of non rectangular shapes and objects bouncing 6 2 Future Work Sofia Micro still has some improvements that could be implemented to increase its effective ness The first is allowing students to interact with actors or the world in a Greenfoot style This would allow students to right click actors and invoke their public methods or right click actors in a sidebar palette to instantiate them This would help encourage students to tinker with the worlds on the fly on mobile devices but this would require a significant amount of work to implement A full Greenfoot style IDE would be ideal however it is much more ambitious Second would be to improve the animation support for some of the microworld scenarios such as the Jeroo example As of right now the jeroo will move instantly to each cell rather than move to the cell over a period of time This would help students visualize what is happening during each act loop Finally Sofia Micro currently only supports ba sic touch events and some key events however there are still other Android specific events that are not supported such as using the accelerometer Improving support for more An droid events would allow students to develop more varied applications within the Sofia Micro framework On the same note the dpad could also be improved to allow support for either multiple dpads at onc
26. ield called Program The program is simply an object which students can either override the myProgram method or write their own program and pass it into the setProgram method Like the ProgrammableActor the ProgrammableWorld uses the beginAtomicAction and endAtomicAction to divide the program into steps Brian L Bowden Chapter 3 Sofia Micro Features 20 ES X Blow Up Free ShakyTower ph X Physics FREE Particle Physics trto G trt FRE ttti FREE RARA tik FRE y Physics Quiz Y a Gravity Sheep FF MiniLand phys Doodle Physics Physics games Space Physics Space Physics L Streaks Phys Bluphys Phys Physics Quiz A PHYSICS bA Cat Physics Electric Space P Cartoon physics Pendulum Lab P kkk REE ttt RE wee ttt REE kkkt FREE ttti REE Ro REE wey y tkt REE ttt FRE ktt REE ttt Figure 3 3 Screenshot of Physics Games on Google Play Store 3 2 Shape and Physics Support Students will be familiar with several physics based Android games such as Angry Birds or some of the apps in Figure 3 3 To help students with writing physics based Android apps we have incorporated 2D shape and physics into Sofia Micro We not only want students to write unique and varied applications but we want them to be able to do it easily By directly incorporating these elements we can allow students to use physics in their game if they wish Sofia supports 2D graphics as well as physics support through JBox2D This allows for inte
27. igned for professionals 14 Android not only retains many of the disadvantages a student would encounter when learning Java but also adds extra complexity in learning the Android framework as well In order to make Android more beginner friendly Sofia the Simplified Open Framework Brian L Bowden Chapter 1 Introduction 3 for Innovative Android Applications was developed as a framework built on top of the Android API to make programming easier and cleaner for both beginners and experts 14 Sofia s primary goal is not to just be a framework used by students for introductory courses but to make Android programming easier and cleaner for both beginners and experts 13 This design goal avoids the drawback of many programming pedagogical frameworks where students eventually hit a ceiling where the framework becomes unusable and students have to stop using the framework altogether 13 Sofia uses a unique event dispatch model to eliminate much of the glue code that is normally required when writing GUIs 15 Sofia also supports 2D shapes with built in physics provided by JBox2D and animation support Sofia makes it easier to switch between different activities and also makes it less cumbersome to reference widgets in a screen 14 However even with Sofia eliminating some of the clunkier portions of writing Android applications the Sofia framework still is not suitable for introductory CS courses and is more suited for students who
28. ion in what students can make so Sofia Micro continues to remain interesting to students Chapter 6 Conclusion Android has significant potential as a learning tool due to its ability to allow users to write concrete and creative applications However due to its learning curve and the fact that it was designed for professionals it is currently not suitable as a learning environment for intro ductory programming courses Sofia Micro aims to fix this issue by creating a microworld friendly environment that emphasizes object oriented and event driven programming on An droid Sofia Micro can leverage Android s strengths while removing much of the complexity that both beginner and expert programmers must learn 6 1 Contributions In this thesis we have shown Sofia Micro s capabilities not just as an Android microworld framework but also as a pedagogical tool that can do more than other microworlds Sofia Micro emphasizes an event driven programming model which has been shown to be an effective programming paradigm for introductory students 20 21 22 Sofia Micro also bridges the gap between different styles of microworlds by supporting both Greenfoot style cellular au tomata actors and Karel style programmable actors We have also added shapes as non actors that can interact with other actors and shapes in the microworld in addition to actors 47 Brian L Bowden Chapter 6 Conclusion 48 and shapes being supported by the p
29. ith some modifications to ensure that physics objects behave properly in the microworld Program is an interface that ProgrammableActor and ProgrammableWorld both implement that allows a user to create a Program that is executed Figure 4 1 Sofia Micro UML Diagram 26 Brian L Bowden Chapter 4 Design amp Implementation 27 Figure 4 2 Sofia Micro Menu step by step Sofia Micro apps have four defined menu items see Figure 4 2 Act Run Pause Reset and Speed Hitting the Act button iterates over each actor and the world once and calls their respective act methods The Run button will cause the World to continuously call the act method on all the actors and the world in addition to allowing physics based objects to run normally After Run is touched Pause will take its place which will stop all actors and the physics simulation Reset will call the initialize method for the screen to reset all the actors and shapes in the world Finally the Speed button will allow users to change the frequency at which the act methods are called when running 4 1 Actors and Programmable Actors Sofia s actors themselves are a shape which as mentioned earlier allows actors to coexist with shapes and also use all of the functionality found in shapes including the physics support Actors extend a shape called DelegatingShape which is a shape itself and also contains Brian L Bowden Chapter 4 Design amp Implementation
30. k Chapter 2 Related Work One issue microworlds try to address is that students have difficulty learning and applying the syntax of a given language For example students who are picking up Java as their initial language may have to write their own main method and class for the typical hello world example such as HelloWorld java public class HelloWorld public static void main String args System out println Hello World Immediately this introduces students to several key ideas in Java such as classes visibility modifiers static keyword return types arguments to a function and arrays One major difference in microworlds is how they address students learning syntax of a language Some microworlds such as Karel avoid this issue by using their own language or set of commands ex Move TurnLeft PickBeeper etc so that the students are introduced to exactly what the microworld wants without students having to worry about all the extra syntax that they will not need until later The downside to this approach is that the students will eventually have to discard this language and relearn a new language Some microworlds Brian L Bowden Chapter 2 Related Work 7 such as Greenfoot instead introduce students to Java albeit with more emphasis on logic rather than syntax This makes the initial learning curve steeper for students but it makes the transition from a CS1 course much easier So
31. lobal clock Students can extend the appropriate actor and override the act method to create behaviors for the actors The programmable actor extends the Actor class and uses Brian L Bowden Chapter 3 Sofia Micro Features 19 a program thread to handle the actor s behavior The entire program logic is written in a Program class which is given to the ProgrammableActor and then executed one step at a time Both actors support similar operations such as changing their position and rotation performing queries on other actors in the world or adding and removing other actors There is a World class that students can extend to create their own World for an application This world class uses a custom thread for the world engine which handles the execution of the world and its actors During each tick of the engine clock the act method is called for the world and all of the actors along with dispatching any buffered events to the world and actors The world uses a grid system similar to Greenfoot where a world is given dimensions in number of cells width x height and how large each cell will be in pixels This allows for programmers to create simple grid worlds with a few number of cells see Section 5 1 or to create a world where each cell is only a pixel to create worlds with more realistic movement see Sections 5 2 or 5 3 Like the programmable actor there is also a ProgrammableWorld that extends the World class which contains a f
32. o Features 25 use of a directional pad dpad that uses its own handler methods listed below e dpadNorthIsDown e dpadNorthEastIsDown e dpadEastIsDown e dpadSouthEastIsDown e dpadSouthIsDown e dpadSouthWestIsDown e dpadWestIsDown e dpadNorthWestIsDown e dpadCenterIsDown When an actor is added to the world that has at least one of these handler methods then the dpad is added to the world in the bottom left corner of the screen The dpad is mostly transparent so it does not obstruct anything behind the dpad when it is moving during an application If a user touches the dpad it will calculate which part of the dpad was touched and automatically call the appropriate handler methods The student can then write the code in these handlers to change the behavior of the actor or the world when one of these handlers is called This gives the student greater control in how they want to move any actor or shape within their scenario since they can opt to use the dpad to manually control the actor or shape rather than letting act or physics engine completely dictate its action Chapter 4 Design amp Implementation Sofia Micro is designed with its predecessors in mind in particular Greenfoot and Karel Sofia Micro uses a relatively few number of classes with the majority of the work being done in the Actor World and WorldView classes By extending the ShapeScreen the WorldScreen can use the shape and physics support w
33. o emphasizes the physics engine of Sofia Micro along with the unique event dispatch that Sofia provides What is different is that Irritated Avians also demonstrates that a world can contain non actor shapes at the same time as regular actors The birds and pigs are actors in this case while the ground slingshot and the white balls the bird leaves behind as it moves are all shapes Of these three the ground is the only one that interacts with the actors by preventing them from leaving the scene This example also demonstrates that actors in Sofia Micro do not necessarily need an act Brian L Bowden Chapter 5 Case Studies 43 method to move if the student does not want to use it movement and collision detection can all be handled by the physics engine This example also emphasizes the event driven nature of both Sofia Micro and Android since all of the interactions in this program are done via the onTouchUp and onTouchMove handlers code for moving the bird before it is shot off public void onTouchMove float x float y float distance Geometry distanceBetween startingPosition x startingPosition y x y float angle Geometry angleBetween startingPosition x startingPosition y x y distance Math min distance 150 0f PointF newPosition Geometry polarShift startingPosition angle distance setPosition newPosition code for flinging the birds once the user stops touching the screen public void onT
34. of Alice since students create programs referred to as scripts by dragging and dropping blocks that represent components in a program such as expressions conditions and loops 16 This allows students to easily create 2 D event driven concurrent programs Brian L Bowden Chapter 2 Related Work 15 CA 7 A Y commands program o o 3 Play p gt Help Send This 0 y Mor QO o Figure 2 7 Screenshot from Daisy the Dinosaur App without requiring students to know and understand all the underlying concepts 17 Scratch differs from other pedagogical tools by focusing on concurrency and event driven program ming early on before moving on to object oriented concepts 17 Scratch also has a large emphasis on social networking by allowing students and teachers to share their projects 16 Scratch s emphasis on students not writing their own code means that it is more appropri ate for a younger audience since younger students tend to struggle more with syntax 33 However like Alice students can quickly master everything Scratch has to offer and the skill ceiling is lower for Scratch since students do not write their own code 2 7 Smart Phone Apps There have been a few apps that have been released on either the Android or iPhone app store that use Karel or Scratch like environments to help teach programming Cato s Hike Brian L Bowden Chapter 2 Related Work 16 teaches p
35. ograms To our knowledge Sofia Micro is the first microworld framework to use event driven programming at all Microworlds such as Karel or Jeroo do not support any kind of event driven style programming however Greenfoot does support a polling style of event handling where actors can ask if a button is pushed down or if the mouse is located in a specific area However Sofia Micro is the first to support a true event driven programming style Students can write event handlers in any of their actors shapes or even the world itself and events will be automatically dispatched to them A list of the supported event handlers are given below Table 3 1 Touch Handler Methods Method Name Description onTouchDown User initially touches the object onScreenTouchDown User intially touches anywhere on the screen onTouchMove User drags their finger in the object onScreenTouchMove User drags their finger anywhere in the screen onTouchUp User lifts their finger in the object onScreenTouchUp User lifts their finger anywhere in the screen onTap User touches then quickly releases their finger in the object onScreenTap User touches then quickly releases their finger anywhere in the screen onDoubleTap User touches then quickly releases their finger two times in a row in the object onScreenDoubleTap User touches then quickly releases their finger two times in a row anywhere in the
36. osaur com Accessed April 17 2014 Hopscotch Hopscotch Coding for Kids 2014 Online Available https www gethopscotch com Accessed April 17 2014 Ants vs Some Bees Object Oriented Tower Defense Ants vs Some Bees 2014 On line Available http nifty stanford edu 2014 denero ants vs somebees Ac cessed April 17 2014 49 Brian L Bowden Chapter 6 Conclusion 50 13 Anthony Allevato Sofia The Simple Open Framework for Inventive Android Applica 14 15 16 17 18 19 20 21 22 23 24 tions 2012 2013 Online Available http sofia cs vt edu sofia 2114 book Accessed January 14 2014 Stephen Edwards and Anthony Allevato Sofia The Simple Open Framework for In ventive Android Applications in ITiCSE 2013 Canterbury England UK 2013 Anthony Allevato and Stephen Edwards A New Event Dispatch Strategy to Eliminate Dispatch Glue in RCTS 2013 Paris France 2013 Orni Meerbaum Salant et al Learning Computer Science Concepts with Scratch in ICER 2010 Aarhus Denmark 2010 Ursula Wolz et al Starting with Scratch in CS1 in SIGCSE 2009 Chattanooga Tennessee USA 2009 Lifelong Kindergarten Group Getting Started With Scratch 2013 Online Available http cdn scratch mit edu scratchr2 static __1397013864__ pdfs help Getting Started Guide Scratch2 pdf Accessed April 8 2014 Stephen Cooper et
37. ouchUp float x float y float dx x startingPosition x float dy y startingPosition y setGravityScale 1 applyLinearImpulse dx 80 dy 80 trailTimer Timer callRepeatedly this leaveTrail 100 5 3 2 Creating Simple Versions of Familiar Android Apps Irritated Avians demonstrates that Sofia Micro addresses both issues in much the same manner as Asteroids Students will be familiar with the Angry Birds game so being able Brian L Bowden Chapter 5 Case Studies 44 Figure 5 5 Ants vs Some Bees UML Diagram to easily write a simplified working version of it would entice many students Students can then make use of Sofia Micro in order to remove much of the complexity to simplify writing the application Students can continue to use Sofia Micro to write unique and varied versions of applications that they would be familiar with which once again extends Sofia Micro s 5 4 Ants vs Some Bees For the last case study a version of Plants vs Zombies was made with the plants replaced with ants and the zombies replaced with bees This game was originally created by UC Berkeley as a nifty assignment to help teach object oriented concepts 12 In this game the ants are trying to repel the bees by shooting leaves at the bees If the bees make contact with the ants then the ants start taking damage until they are removed from the game Brian L Bowden Chapter 5 Case Studies 45 Food 17 Figure
38. ounce off each other apply forces or use acceleration much easier since the student does not have to explicitly change the movement of the actor themselves and let the physics engine handle it This eases a significant portion of the burden of moving actors in a world since students no longer need to calculate the velocity or position themselves they can instead just let the physics engine worry about that 3 3 Event Driven Programming amp Event Dispatch Kim Bruce et al in Java An Eventful Approach discuss how event driven programming is an appropriate programming paradigm for students because most real world applications will be GUI based as opposed to command line based 20 They also emphasize in their other works that students can quickly pick up event handling since they can focus on parameters and methods along with the amount of code they have to write to do something interesting is very small 21 22 23 Given Android s focus on event driven programming in general Sofia s microworld was designed to support touch and key events so that students can write event driven programs themselves This emphasis on event driven programming differenti Brian L Bowden Chapter 3 Sofia Micro Features 23 ates Sofia Micro from other microworlds which may not feature any event driven support at all Students can still use an imperative programming paradigm for their programs if they wish but they have the option for event driven style pr
39. ow for a natural progression from a microworld environment to a mobile environment 1 4 Solution We propose Sofia Micro a pedagogical tool for creating microworlds that extends the Sofia framework to help students learn Android programming in an easy to use Greenfoot style environment This microworld framework aims to simplify the Android framework so that in troductory level students can reap the benefits of Android and to also modernize microworlds in general by adding additional features that have not been used before in a microworld en vironment so that they can span a full CS1 course Sofia Micro focuses on event driven programming which helps emphasize the strengths of the Android framework Sofia Micro Brian L Bowden Chapter 1 Introduction 5 supports both the cellular automata style actors of Greenfoot and the programmable actor style of Karel actors even in the same world Finally it supports having non actor shapes in the world as well and both actors and shapes support physics interactions with each other This thesis is broken down in the following manner Chapter 2 covers related work and discusses previous microworlds in more detail Chapter 3 covers the features of Sofia Micro with Chapter 4 discussing the design and implementation of these features Chapter 5 presents some case studies to demonstrate the capabilities and ease of use of Sofia Micro features with Chapter 6 covering concluding remarks and future wor
40. r worlds with a few cells see Section 5 1 then the bounds is set to be from 0 48 to 0 48 for both the width and height Sofia automatically centers the shape in the middle of the cell and because the bounds are the center of the cell 0 48 then when a student accesses cell x y they are referring to the center of the cell rather than the top left corner of the cell To avoid edge cases where the bounds are touching at the edges the bounds Brian L Bowden Chapter 4 Design amp Implementation 29 use 0 48 rather than 0 5 In the case of the scale to cell flag being set to false then the bounds are merely the bounds of the image scaled to the world which is typically used when the world has very small grid cells such as in the Asteroids example where the world is a 500x500 world with grids 1 pixel wide When an actor is added to the world the programmer can specify which x y co ordinate to add the actor to otherwise the actor will be added at coordinate 0 0 by default Once added to the world programmers can use several of the actor s meth ods to move or rotate it such as move int distance setX float x setY float y setRotation float angle and other methods to help the actor find other shapes or ac tors for querying or collision detection such as getNeighbors getObjectsAtOffset or getIntersectingObjects As mentioned earlier students will extend the Actor class with their subclasses that will then ove
41. ractions and behaviors such as gravity collisions detection objects bouncing and objects sliding By utilizing the physics engine a programmer can greatly simplify the amount of code they need to write in order to have some basic physics in a game or application Since Sofia Micro is an extension to Sofia then Sofia Micro can employ both the shape and physics support to add functionality that is not previously seen before in a microworld This allows Brian L Bowden Chapter 3 Sofia Micro Features 21 for shapes to coexist with actors in a world and since actors are also shapes themselves then the two can interact with each other and be affected by physics such as collision detection or forces The shape support allows students greater flexibility in what is placed in each world Students no longer need to use an actor for every object in the world if they do not need to and can instead use simple 2D shapes when appropriate This helps clean up some of the code since the student does not need to explicitly write an actor for some simple behaviors Sofia Micro support lines rectangles ovals and polygon shapes so the student can use these to create objects such as projectiles in a game or walls and platforms for a side scroller This also allows students to write simple GUI applications such as a Paint application that lets the user draw basic shapes on the screen With Sofia Micro s physics engine students can easily create physic
42. rogramming in a Karel like fashion where students program a child to navigate mazes to collect hearts or stars 9 Daisy the Dinosaur is similar to Scratch in that users drag and drop actions in order to control the dinosaur on screen see 2 7 10 Hopscotch also uses a Scratch like approach to teach students to code by dragging and dropping blocks to create games or animations 11 All of these apps are targeted to students around the ages of 8 10 which makes them ideal for introducing students at a young age to programming logic They also demonstrate how smart phones and tablets can act as a motivator for students to learn programming Chapter 3 Sofia Micro Features Sofia Micro has several novel features that have not been used before in microworlds or microworld frameworks In addition to supporting Android apps Sofia Micro has the ability to support both types of actors commonly seen in microworlds Sofia Micro also supports 2D shapes and physics simulation for actors and shapes Sofia Micro is the first microworld framework that supports event driven style programming 3 1 Actors and Programmable Actors Microworlds typically use one of two different strategies for defining the behavior of actors Karel and later Jeroo and Kara used what we will call programmable actors In this type of actor the entire program is written for the actor and then executed one step at a time Students have to write out the entire logic for their
43. roworld context and allowing for both Greenfoot style actors and Karel style actors in the same world Acknowledgments I would like to thank Dr Edwards for helping me with my thesis and for his assistance during grad school I would also like to thank my friends and family for their support during my time in grad school ill 1 Introduction 1 1 Necro worlds sudo cache Me be ate Me ds och NE ed A ce oa eR A 1 3 Problem Statement ela ela ette LA SOMO A E ee E a Shae eas 2 Related Work 20 Karelson A og E Boks EEE rh 22 ICR i A A DG hack A OS 29 Stele ie fe A a a ee ae ee Te ek 24 Jero and Kara y do a Boke aod nok Ped Rk 25 ASTCOMMOOL teta tao Ze Bade tds ett XO sm e 252 2 eo G8 E ky pcan aes 2 7 Smart Phone Apps es e dey She SHA a 3 Sofia Micro Features 3 1 Actors and Programmable Actors 3 2 Shape and Physics Support eos lt lt lt e 4 yg a hes 3 3 Event Driven Programming amp Event Dispatch 4 Design amp Implementation 4 1 Actors and Programmable Actors Contents Rh wo NO HE O 4 2 Shape and Physics in Sofia oa Soe te we SCA we Bode aes a es 30 4 3 Event Wis pauls 2442s b bd gels h hh a he Som heel bole nw eh dow Sb 32 JA Directional Padis e smg sie t atse A wR Oe a PO ae D 34 5 Case Studies 36 DL IET a a e a A a Sk eR Soe Beh a Bait oS 36 5 1 1 Actors and Programmable Actors ooa a a 36 5 1 2 Simple Microworlds on Android esa 38 Died AS
44. rride the act method with their own implementation The World class s Engine inner class will call the act method on every actor every tick of the clock Actors and shapes that are added or removed during the act of another actor are placed in a list named deferredAdds or deferredRemoves which is dealt with after all the act methods have been called This avoids the issue of synchronization concurrent modification exceptions on the list of actors and also helps ensure that the order of actors does not cause exceptions or abnormal behavior Brian L Bowden Chapter 4 Design amp Implementation 30 4 2 Shape and Physics in Sofia Sofia s shape model first begins with the abstract class called Shape that every other shape will extend The shape contains several fields including the color alpha rotation as well as some fields for JBox2D such as a Body density and friction Subclasses of Shape such as oval rectangle or polygon shapes will provide functionality for the bounds and fixtures for the shape The physics is provided primarily by JBox2D which handles much of the collision detection applying forces to shapes and moving the shapes Users can apply forces to a shape such as gravity using the setGravity PointF method or give the shape a linear velocity using setLinearVelocity PointF Users can also specify how a shape interacts with other shapes by using the setShapeMotion method to specify if the shape is dynami
45. s They are later unmasked in the dispatch method for the DpadDispatcher The dpad is not added to the world by default instead when a student adds an actor to the world the world will check to see if the actor has any dispatch able dpad methods If the actor does have some dispatch able methods then the dpad will be added to the bottom left corner of the screen This simplifies the code for the student since they do not have to explicitly add the dpad themselves and do not have to calculate the bounds of the dpad Chapter 5 Case Studies To demonstrate the capabilities of the new features for Sofia Micro we have implemented a few classic Greenfoot examples in addition to writing a few of our own examples 5 1 Jeroo As mentioned in Chapter 2 a jeroo is a kangaroo like animal on an island that hops around collecting flowers while avoiding traps Jeroo is similar to Karel in that it also uses the programmable actor found in Karel and other similar microworlds Sofia Micro has a built in jeroo package along with Lightbot and Greenfoot so students who wish to use it can simple extend or use the appropriate jeroo classes 5 1 1 Actors and Programmable Actors Jeroo emphasizes the actor aspects of Sofia Micro namely the actor and programmable actor The jeroo itself is a programmable actor where students write their logic in the myProgram method An example of some of the logic for a jeroo program is given below 3
46. s based games such as Asteroids see Section 5 2 Angry Birds see Section 5 3 or Plants vs Zombies see Section 5 4 By utilizing the physics engine students can write code for moving and de tecting actors or shapes in a cleaner fashion For example rather than using the move method in actor to move an actor can instead say that it is a dynamic object and give itself a linear velocity This may not look much different but since the actor is moving by the physics engine rather than being manually moved by the user then it collides and reacts to the environment in a more realistic fashion This also avoids the issue of a fast moving actor moving past another actor completely since a physics actor will be moved more frequently The physics engine supports three different types of physics objects static kinematic Brian L Bowden Chapter 3 Sofia Micro Features 22 and dynamic objects Static objects can not be moved except by explicitly changing their position x or y coordinate and they do not participate in collisions with other static or kinematic objects 3 Kinematic objects are similar to static objects except they can have a non zero velocity 3 Like static objects however they have infinite mass and do not collide with other static or kinematic objects 3 Lastly dynamic objects are simulated objects that move by forces collisions velocity etc and will respond to collisions with other objects 3 Dynamic actors can b
47. students to drag and drop actions and observe an avatar perform those actions rather than writing the code themselves 2 Students can drag and drop actions in this manner to create a story or an interactive game 2 This approach to programming allows for easy experimentation by the students and for them to use their own creativity One of the important ideas with Alice along with Scratch is that students can not write Brian L Bowden Chapter 2 Related Work 10 E BlueJ people2 Project Edit Tools View Help New Class gt ESA Compile View lv Uses lv Inheritance staff_1 Staff Creating object Done Figure 2 3 BlueJ Class Layout 26 syntactically incorrect code which removes one of the hardest hurdles for students who are first learning to program and instead allows the student to focus on the logic of the program 2 Like Karel however Alice suffers from many of the same drawbacks since students are not actually writing any code themselves and they are limited to the tools Alice provides for them 2 3 BlueJ BlueJ is a pedagogical Java IDE designed to help teach object oriented programming that uses the standard Java JDK compiler and virtual machine 26 BlueJ is based on three design goals interactivity visualization and simplicity 27 BlueJ uses a simpler interface to reduce the complexity that many students must overcome when learning to use an IDE Brian
48. students to grasp 4 28 Both tools have been well received by students however they have the same drawbacks as Karel since students are still only limited to a single scenario and programming a single type of actor Brian L Bowden Chapter 2 Related Work 12 Kara the programmable ladybug Figure 2 4 Kara Sample Program 4 2 5 Greenfoot Greenfoot is an integrated development environment IDE that aims to teach Java program ming 25 A 2D grid is used with the origin 0 0 being in the top left corner so students can address a given cell in the same way a 2D array would be indexed 25 This grid represents a world which can contain objects referred to as actors 7 25 Every Greenfoot scenario will contain at least one class that extends World and one or more classes that extend Actor Brian L Bowden Chapter 2 Related Work 13 Actor classes Actor classes Open editor Set image Remove New subclass a E Figure 2 5 Greenfoot Wombats example 24 25 Actors contain an act method which defines what each actor will do during each tick of the world timer and is where students write the majority of their programs This paradigm of how students program actors closely follows the cellular automata idea where each object responds to their immediate surroundings and reacts accordingly Greenfoot also contains a simple user interface for students to use which removes much of the advanc
49. ues are also stored in the wrapper for motion events so they can also be dispatched to the world or actors To help with dispatching events a TouchDispatcher class was created This class has a static dispatchTo method that takes in the object to dispatch the event to the event itself along with its action code and a PointF object that contains the x and y coordinate where the event occurred For Sofia Micro this x y coordinate pair will be the grid location Brian L Bowden Chapter 4 Design amp Implementation 34 otherwise it will just be the motion event s getX and getY In order to speed up the dispatch portion when the world is dispatching the events to all the actors a static hasDispatchableEvents method is used which will return true if the actor has any motion event handlers so that dispatching events is skipped for actors that have no event handlers After the motion and key events have been dispatched to all the actors and worlds then the buffers being used are cleared and then swapped so the next iteration of the run loop in the Engine will use the other buffer 4 4 Directional Pad Sofia Micro s directional pad dpad is implemented as a shape that extends the Rectan gleShape class with a dpad image see Figure 4 4 Touch events are dispatched to the dpad before being dispatched to the actors and the world The dpad contains motion event handlers for onTouchDown onTouchUp and onTouchMove that catches
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