Description
1. Introduction
The purpose of this assignment is to help you gain experience with interactive graphics
and animation techniques such as repainting, timer-driven animation, collision detection, and
object selection. Specifically, you are to make the following modifications to your game:
(1) the game world map is to display in the GUI (in addition to the text form on the console),
(2) the movement (animation) of game objects is to be driven by a timer,
(3) the game is to support dynamic collision detection and response,
(4) the game is to support simple interactive editing of some of the objects in the world, and
(5) the game is to include sounds appropriate to collisions and other events.
2. Game World Map
If you did Assignment#2 (A#2) properly, your program included an instance of a
MapView class which is an observer that displayed the game elements on the console.
MapView also extended Container and that panel was placed in the middle of the game
frame, although it was empty.
For this assignment, MapView will display the contents of the game graphically in the
container in the middle of the game screen (in addition to displaying it in the text form on the
console). When the MapView update() is invoked, it should now also should call
repaint() on itself. As described in the course notes, MapView should override paint(),
which will be invoked as a result of calling repaint(). It is then the duty of paint() to
iterate through the game objects invoking draw() in each object – thus redrawing all the
objects in the world in the container. Note that paint() must have access to the GameWorld.
That means that the reference to the GameWorld must be saved when MapView is
constructed, or alternatively the update() method must save it prior to calling repaint().
Note that the modified MapView class communicates with the rest of the program exactly as it
did previously (e.g., it is an observer of GameWorld).
As indicated in A#1, each type of game object has a different shape which can be
bounded by a square. The size attribute provides the length of this bounding square. The
different graphical representation of each game object is as follows: Bases are filled isosceles
triangles; energy stations are filled circle; the player robot is a filled square while non-player
robots are unfilled square; and drones are unfilled isosceles triangles. Hence, the size attribute
of an energy station indicates the diameter of the circle, size of a base or drone indicates the
length of the unequal side and height of the isosceles triangle, and size of a robot indicates the
length of equal sides of the square.
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Bases should include a text showing their number; energy stations should include a text
showing their capacity. Use the Graphics method drawString() to draw the text on bases
and energy stations.
The appropriate place to put the responsibility for drawing each shape is within each
type of game object (that is, to use a polymorphic drawing capability). The program should
define a new interface named IDrawable specifying a method draw(Graphics g,
Point pCmpRelPrnt). GameObject class should implement this interface and each
concrete game object class should then provide code for drawing that particular object using
the received Graphics object g (which belong to MapView) and Point object
pCmpRelPrnt, which is the component location (MapView’s origin location which is located at
its the upper left corner) relative to its parent container’s origin (parent of MapView is the
content pane of the Game form and origin of the parent is also located at its upper left corner).
Remember that calling getX() and getY() methods on MapView would return the MapView
component’s location relative to its parent container’s origin.
Each object’s draw() method draws the object in its current color and size, at its
current location. Recall that current location of the object is defined relative to the origin of the
game world (which corresponds to the origin of the MapView in A#2 and A#3). Hence, do not
forget to add MapView’s origin location (relative to its parent container’s origin) to the current
location while drawing your game objects since draw…() methods (e.g., drawRect()) of
Graphics expects coordinates which are relative to the parent container’s origin. Also, recall
that the location of each object is the position of the center of that object. Each draw()
method must take this definition into account when drawing an object. Remember that the
draw…() method of the Graphics class expects to be given the X,Y coordinates of the
upper left corner of the shape to be drawn. Thus, a draw() method would need to use the
location and size attributes of the object to determine where to draw the object so its center
coincides with its location (i.e., the X,Y coordinate of the upper left corner of a game object
would be at center_location.x – size/2, center_location.y – size/2 relative
to the origin of the MapView, which is the origin of the game world).
3. Animation Control
The Game class is to include a timer (you should use the UITimer, a build-in CN1
class) to drive the animation (movement of movable objects). Game should also implement
Runnable (a build-in CN1 interface). Each tick generated by the timer should call the run()
method in Game. run() in turn can then invoke the “Tick” method in GameWorld from the
previous assignment, causing all moveable objects to move. This replaces the “Tick” button,
which is no longer needed and should be eliminated.
There are some changes in the way the Tick method works for this assignment. In order
for the animation to look smooth, the timer itself will have to tick at a fairly fast rate (about
every 20 msec or so). In order for each movable object to know how far it should move, each
timer tick should pass an “elapsed time” value to the move() method. The move() method
should use this elapsed time value when it computes a new location. For simplicity, you can
simply pass the value of the timer event rate (e.g., 20 msec), rather than computing a true
elapsed time. However, it is a requirement that each move() computes movement based on
the value of the elapsed time parameter passed in, not by assuming a hard-coded time value
within the move() method itself. You should experiment to determine appropriate movement
values (e.g., in A#1, we have specified the initial speed of the drone to be a random value
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between 5 and 10, you may need to adjust this range to make your drones have reasonable
speed which is not to too fast or too slow). In addition, be aware that methods of the built-in
CN1 Math class that you will use in move() method (e.g., Math.cos(), Math.sin())
expects the angles to be provided in radians not degrees. You can use
Math.toRadians()to convert degrees to radians. Likewise, the built-in
MathUtil.atan() method that you might have used in the strategy classes also produces
an angle in radians. You can use Math.toDegrees()to convert degrees to radians.
Remember that a UITimer starts as soon as its schedule() method is called. To
stop a UITimer call its cancel() method. To re-start it call the schedule() method again.
4. Collision Detection and Response
There is another important thing that needs to happen on Tick method in GameWorld.
After invoking move() for all movable objects, your Tick method must determine if there are
any collisions between objects, and if so to perform the appropriate “collision response”. You
must handle collision detection/response by having GameObject class implement a new
interface called “ICollider” which declares two methods
boolean collidesWith(GameObject otherObject) and
void handleCollision(GameObject otherObject) which are intended for
performing collision detection and response, respectively.
In the previous assignment, collisions were caused by pressing one of the “pretend
collision buttons” (i.e., “Collide With NPR”, “Collide With Base”, “Collide With Drone”, “Collide
with Energy Station”) and the objects involved in the collision were chosen arbitrarily. Now, the
type of collision will be detected automatically during collision detection, so the pretend
collision buttons are no longer needed and should be removed. Collision detection will require
objects to check to see if they have collided with other objects, so the actual collisions will no
longer be arbitrary, but will correspond to actual collisions in the game world. There are more
hints regarding collision detection in the notes below.
Collision response (that is, the specific action taken by an object when it collides with
another object) will be similar as before. Hence, handleCollision() method of a game
object should call the appropriate collision handling method in GameWorld from the previous
assignment. Collisions also generate a sound (see below) and thus, collision handling
methods in GameWorld should be updated accordingly.
In addition to the player robot, NPRs can also collide with other NPRs, bases, drones,
and energy stations. The effects of these collisions on an NPR would be the same as the
effects caused by these collisions on the player robot (i.e., collision with other NPR would
increase damage level and fade color of both NPRs, collision with base would increase the
lastBaseReached value of the NPR given that the base number is one more than the current
lastBaseReached value, collision with a drone would increase the damage level of the NPR,
collision with an energy station would increase NPR’s energy level, reduce capacity of the
energy station to zero, fade the color of the energy station, and add a new energy station).
Finally, since we now automatically detect collisions, we do not need to (and thus, we
should not) assign the next lastBaseReached value to NPRs each time “Change Strategies”
button is hit. This value of the NPR will now be updated as a result of collisions with the bases.
In addition, although we still assume that NPRs never run out of energy, collision between a
NPR and an energy station would increase the energy level of the NPR.
5. Sound
You may add as many sounds into your game as you wish. However, you must
implement particular, clearly different sounds for at least the following situations:
(1) when robots collides, e.g., a player robot-NPR or NPR-NPR collision happens (such as a
crash sound),
(2) when a robot (NPR/player robot) collides with an energy station (such as an electric
charge sound),
(3) any collision which results in the player robot losing a life (such as an explosion or dying
sound),
(4) some sort of appropriate background sound that loops continuously during animation.
Sounds should only be played if the “Sound” attribute is “On”. Note that except for the
“background” sound, sounds are played as a result of executing a collision. Hence, you must
play these sounds in collision methods in GameWorld.
You may use any sounds you like, as long as I can show the game to the Dean and your
mother (in other words, they are not disgusting or obscene). Short, unique sounds tend to
improve game playability by avoiding too much confusing sound overlap. Do not use
copyrighted sounds. You may search the web to find these non-copyrighted sounds (e.g.,
www.findsounds.com).
You must copy the sound files directly under the src directory of your project for CN1 to
locate them. You should add Sound and BGSound classes to your project to add a capability
for playing regular and looping (e.g., background) sounds, respectively, as discussed in the
lecture notes. These classes encapsulate given sound files by making use of InputStream,
MediaManager, and Media build-in CN1 classes. In addition to these built-in classes,
BGSound also utilizes Runnable build-in CN1 interface. You should create a single sound
object in GameWorld for each audio file and when you need to play the same sound file, you
should use this single instance (e.g., all robot and energy station collisions should use the
same sound object).
6. Object Selection and Game Modes
In order for us to explore the Command design pattern more thoroughly, and to gain
experience with graphical object selection, we are going to add an additional capability to the
game. The game is to have two modes: “play” and “pause”. The normal game play with
animation as implemented above is “play” mode. In “pause” mode, animation stops – the game
objects don’t move, the clock stops, and the background looped sound also stops. Also, when
in pause mode, the user can use the pointer to select some of the game objects as explained
below.
Ability to select the game mode should be implemented via a new GUI command button
that switches between “play” and “pause” modes (you should create an additional command
class to handle action events generated by this button and set its target as Game). When the
game first starts it should be in play mode, with the mode control button displaying the label
“Pause” (indicating that pushing the button switches to pause mode). Pressing the Pause
button switches the game to pause mode and changes the label on the button to “Play”,
indicating that pressing the button again resumes play and puts the game back into play mode
(also restarting the background sound, if sound is enabled).
– Object Selection
When in pause mode, the game must support the ability to interactively select objects.
To identify “selectable” objects, you should have those objects implement an interface called
ISelectable which specifies the methods required to implement selection, as discussed in
the lecture notes. Selecting an object allows the user to perform certain actions on the
selected object. For this assignment, all Fixed objects (Energy Stations and Bases) are
selectable. The selected energy station/base must be highlighted by drawing it as an un-filled
circle/triangle (a normal energy station/base is drawn as a filled circle/triangle). Selection is
only allowed in pause mode, and switching to play mode automatically “unselects” the object.
An individual object is selected by pressing the pointer on it. Pressing on an object
selects that object and “unselects” all other objects. Clicking in a location where there are no
objects causes the selected object to become unselected. Remember that pointer (x,y)
location received by overriding the pointerPressed() method of MapView is relative to
screen origin. You can make this location relative to MapView’s parent’s origin by calling the
following lines inside the pointerPressed() method:
x = x – getParent().getAbsoluteX()
y = y – getParent().getAbsoluteY()
A new Position command (which should extend from Command as the other
commands of the game) is to be added to the game, invocable from a new “Position” button.
When the position command is invoked, the selected energy station or base is to be moved to
a new location. This movement should be done by following the below steps in the given
order: 1) Select the object 2) Hit Position button 3) Click on MapView to select a new position
for the selected object 4) Selected object would appear in the new location. The position
action should only be available while in pause mode, and should have no effect on unselected
objects. Note that the new position command gives the user the ability to create an arbitrary
track configuration; the game is no longer constrained to use the hard-coded initial layout
provided when the game starts or life is lost.
To execute the position command properly in A#3, we remove the requirement that was
introduced in A#1 that restricted all fixed game objects from changing location once they are
created. Also, note that regardless of their capacity all energy stations are allowed to be
moved.
– Command Enabling/Disabling
Commands should be enabled only when their functionality is appropriate. For example,
the Position command should be disabled while in play mode; likewise, commands that involve
playing the game (e.g., changing the player robot direction) should be disabled while in pause
mode. Note that disabling a command should disable it for all invokers (buttons, keys, and
menu items). Note also that a disabled button or menu item should still be visible; it just cannot
be active (enabled). This is indicated by changing the appearance of the button or menu item.
To disable a button or a menu item which is added to the form by
addComponentToSideMenu() use setEnabled() method of Button (remember that
Checkbox is-a Button). To disable a menu item which is added to the form by
addCommandToSideMenu() use setEnabled() method of Command. To disable a key,
use removeKeyListener() method of Form (remember to re-add the key listener when the
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command is enabled). You can set disabled style of a button using
getDisabledStyle().set…() methods on the Button.
Additional Notes
• Please make sure that in A#2 you have added a MapView object directly to the center of
the form. Adding a Container object to the center and then adding a MapView object
onto it would cause incorrect results when a default layout is used for this center container
(e.g., you cannot see any of the game objects being drawn in the center of the form).
• To draw a un-filled and filled triangle you can use drawPolygon()/fillPolygon()
methods of Graphics. These methods expect the following parameters: xPoints which
is an array of integers that has x coordinates of the corners, yPoints which is an array of
integers that has y coordinates of the corners, nPoints which is the integer that indicates
the number of corners of the polygon. For instance, to draw a triangle with corner
coordinates (1,1) (3,1) (2,2), you should assign xPoints = {1,3,2}, yPoints = {1,1,2},
nPoints = 3.
• To draw a filled circle with radius r at location (x,y)use fillArc(x, y, 2*r, 2*r,
0, 360).
• As before, the origin of the game world (which corresponds to the origin of the MapView for
now) is considered to be in its lower left corner. Hence, the Y coordinate of the game world
grows upward (Y values increase upward). However, origin of the MapView container is at
its upper left corner and Y coordinate of the MapView grows downward. So when a game
object moves north (e.g., it’s heading is 0 and hence, its Y values is increasing) in the
game world, they would move up in the game world. However, due to the coordinate
systems mismatch mentioned above, heading up in the game world will result in moving
down on the MapView (screen). Hence your game will be displayed as upside down on the
screen. This also means that when we robots turn left they will go west in game world, but
they will go east on the MapView (and turning right means going west on the MapView). In
addition, triangles (e.g. bases and drones) will be drawn upside down in MapView. Leave it
like this – we will fix it in A#4.
• The simple shape representations for game objects will produce some slightly weird visual
effects in MapView. For example, squares or triangles will always be aligned with the X/Y
axes even if the object being represented is moving at an angle relative to the axes. This
is acceptable for now; we will see how to fix it in A#4.
• You may adjust the size of game objects for playability if you wish; just don’t make them so
large (or small) that the game becomes unwieldy.
• As indicated in A#2, boundaries of the game world are equal to dimensions of MapView.
Hence, drones should consider the width and the height of MapView when they move, not
to be out of boundaries.
• Because the sound can be turned on and off by the user (using the menu), and also turns
on/off automatically with the pause/play button, you will need to test the various
combinations. For example, turning off sound, then pressing pause, then pressing play,
should result in the sound not coming back on. There are several sequences to test.
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• When two objects collide handling the collision should be done only once. For instance,
when two robots collide (i.e., robot1 and robot2) the robots damage level should be
increased only once, not twice. In the two nested loops of collision detection,
robot1.collidesWith(robot2) and robot2.collidesWith(robot1) will both
return true. However, if we handle the collision with
robot1.handleCollision(robot2) we should not handle it again by calling
robot2.handleCollision(robot1). This problem is complicated by the fact that in
most cases the same collision will be detected repeatedly as one object passes through
the other object. Another complication is that more than two objects can collide
simultaneously. One straight-forward way of solving this complicated problem, is to have
each collidable object (that may involve in such a problem) keep a list of the objects that it
is already colliding with. An object can then skip the collision handling for objects it is
already colliding with. Of course, you’ll also have to remove objects from the list when they
are no longer colliding.
Implementation of this solution would require you to have a Vector (or Arraylist) for
each collidable object (i.e., all game objects in Robo-Track game) which we will call as
“collision vector”. When collidable object obj1 collides with obj2, right after handling the
collision, you need to add obj2 to collision vector of obj1. If obj2 is also a collidable object,
you also need to add obj1 to collision vector of obj2. Each time you check for possible
collisions (in each clock tick, after the moving the objects) you need to update the collision
vectors. If the obj1 and obj2 are no longer colliding, you need to remove them from each
other’s collision vectors. You can use remove() method of Vector to remove an object
from a collision vector. If two objects are still colliding (passes through each other), you
should not add them again to the collision vectors. You can use contains() method of
Vector to check if the object is already in the collision vector or not. The contains()
method is also useful for deciding whether to handle collision or not. For instance, if the
collision vector of obj2 already contains obj1 (or collision vector of obj1 already contains
obj2), it means that collision between obj1 and obj2 is already handled and should not be
handled again.
• You should tweak the parameters of your program for playability after you get the
animation working. Things that impact playability include object sizes and speeds, etc.
Your game is expected to operate in a reasonably-playable manner.
• As before, you may not use a “GUI Builder” for this assignment.
• All functionality from the previous assignment must be retained unless it is explicitly
changed or deleted by the requirements for this assignment.
• Your program must be contained in a CN1 project called A3Prj. You must create your
project following the instructions given at “2 – Introduction to Mobile App Development and
CN1” lecture notes posted at Canvas (Steps for Eclipse: 1) File → New → Project →
Codename One Project. 2) Give a project name “A3Prj” and uncheck “Java 8 project” 3) Hit
“Next”. 4) Give a main class name “Starter”, package name “com.mycompany.a3”, and
select a “native” theme, and “Hello World(Bare Bones)” template (for manual GUI building).
5) Hit “Finish”.). Further, you must verify that your program works properly from the
command prompt before submitting it to Canvas (Get into the A3Prj directory and type
“java -cp dist\A3Prj.jar;JavaSE.jar com.codename1.impl.javase.Simulator
com.mycompany.a3.Starter” for Windows machines. For the command line arguments of
Mac OS/Linux machines please refer to the class notes.). Substantial penalties will be
applied to submissions which do not work properly from the command prompt.
Deliverables
Submitting your program requires the same three steps as for A#1 and A#2 except that
you do not need to submit a UML for A#3:
1. Be sure to verify that your program works from the command prompt as explained above.
2. Create a single file in “ZIP” format containing (1) the entire “src” directory under your CN1
project directory (called A3Prj) which includes source code (“.java”) for all the classes in your
program and the audio files, and (2) the A3Prj.jar (located under the “A3Prj/dist” directory)
which is automatically generated by CN1 and includes the compiled (“.class”) files for your
program in a zipped format. Be sure to name your ZIP file as YourLastName-YourFirstNamea3.zip.
3. Create a “TEXT” (i.e., not a pdf, doc etc.) file called “readme-a3.txt” that includes your name
and whether you have tested your submission on a lab machine. You are strongly
encouraged to run and test your program on a lab machine (Hydra terminal server is
recommended) before submitting your project. If you have done this test, also specify the lab
number and the name of the specific machine you have used in that lab (or if you have used
Hyrda as recommended, just say it was tested on Hydra) in the text file. In addition, if you have
done this test, be sure that you include the src folder and jar file generated/tested on the lab
machine in the above-mentioned zip file. This information helps the grader in case your
submission does not work on the machine (s)he uses. You may also include additional
information you want to share with the grader in this text file. You will receive the grader
comments on your text file when grades are posted.
4. Login to Canvas, select “Assignment#3”, and upload your ZIP file and TEXT file separately
(do NOT place this TEXT file inside the ZIP file). Also, be sure to take note of the requirement
stated in the course syllabus for keeping a backup copy of all submitted work (save a copy of
your ZIP and TEXT files).
All submitted work must be strictly your own!
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Appendix 1: Sample GUI
The following shows an example of how a completed A#3 game might look. It has a
control panel on the left, right, and bottom with the required command buttons. Notice that the
bottom control container does not have the Collide With NPR, Collide With Base, Collide With
Drone, Collide With Energy Station buttons as in A#2 GUI, instead it has the Pause/Play and
Position buttons. Position button is disabled since the game here is in “Play” mode as
indicated by the fact that the Pause/Play button shows “Pause”. MapView in the middle
contains 4 bases (blue filled triangles), 2 energy stations (green filled circles), 1 player robot
(red filled square), 3 NPRs (red unfilled squares), and 2 drones (black unfilled triangles).
Bases and energy stations include a text showing their number and capacity, respectively. As
indicated in A#1, all bases and all robots have the same size whereas sizes of the rest of the
game objects are chosen randomly when created. The initial capacity of an energy station is
proportional to its size. Note also that the world is “upside down” (e.g., the triangles are facing
down). We will fix this in A#4.
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