PIIT Computer Science
Summer Camp - Alice
July 11, 2012
Brenda Parker
Computer Science Department
MTSU
Welcome
• Review??
• Demonstrations?
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Today’s Topics
• Event Programming
– Event
– Event handler
• Interactive Programming
• Billboards
• Games
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Event-Driven
Programming
Event – special condition that occurs
while a program is running (event
trigger)
Event Handler – method that executes
when an event has occurred.
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Sample Events
• The user presses the left mouse
button
• The user presses a key on the
keyboard
• The user presses the space bar on
the keyboard
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Event Handlers
We must create “event handlers” – we
must create methods to tell the
computer what to do if an event
occurs!
What do we do if the user presses the
spacebar?
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Events and Event Handlers use
Interactive Programming
• Interactive
– User participates while the video is
playing
– When the user clicks mouse or presses a
key, an event occurs and must be
handled by a given method
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Event Programming
1. Click “create new event” in the
Events Editor Window
2. Choose desired event
3. Create method to handle the event
4. Play and save video
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Simple Example of
Event and Event Handlers
Suppose that we wish to create a video
which contains a fish swimming in the
ocean by an island. The fish jumps out of
the water when the user presses the space
bar.
EVENT: user presses the space bar
EVENT HANDLER: a method indicating what
to do when the space bar is pressed
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Fish Example
1. Open Alice and create the original
scene.
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Fish Example
2. Create the code to allow the fish to
swim (forever).
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Fish Example
3. Create a world method to tell the
fish to jump out of the water.
a.Select the world object
b.Choose “create new method”
c.Name the method (jumpOut)
d.Write the method
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Fish Example
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Fish Example
4. Create the Event
a. In the Events Area, click on
“create new event”
b. Click on “when key is typed”
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Fish Example
c. Replace “any key” with “Space”
d. Replace “do nothing” with “jumpOut”
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Fish Example
5. Play the video.
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Practice X
Choose from any one of the following to create
“interactive” programming. Save the file!
1. Create a boat scene in which the boat moves to the
right when the right arrow key is pressed and moves to
the left when the left arrow key is pressed.
2. Create a scene with 2 penguins (Sam and Joe). When
the user presses “J” on the keyboard, Joe jumps or
flaps his wings. When the user presses “S”, Sam jumps
and flaps his wings.
3. Create your own scene which allows user input of some
type.
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User Input
If a program (video) requires
interactive input, the user should be
given instructions on what to input.
Example: In the “fishJump.a2w” video,
the user should be told to press the
space bar to make the fish jump.
User Input
The user should be given a set of
instructions to read when the world
first starts.
These instructions can be displayed in
Alice with a “billboard”
A billboard is a picture file that is
added to an Alice world.
Displaying User
Instructions
1. Use Microsoft Word to create the
instructions.
2. Use Copy and Paste to place the
image into Microsoft Paintbrush or
Paint and save the file as a picture
(jpg or gif).
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1.
2.
3.
4.
5.
6.
7.
Practice XI
Create Instructions
Open Word
Type in instructions
Format instructions
Copy instructions
Open Paint
Paste instructions
Save your picture as jump.jpg
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Instructions created in
Microsoft Word
Displaying Game
Instructions
3. In Alice, FileMake Billboardselect
your instructions picture.
4. Position your billboard in your Alice world
so that it is displayed appropriately.
5. Make all other objects invisible
(propertiesis showing=false)
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Billboard is visible!
Practice XII
1. Use Microsoft Word to create
instructions for your Practice X
program.
2. Copy the instructions. (Control + C)
3. Open Microsoft Paint
4. Paste the instructions (Control+P)
5. Save your instructions
(instructions.jpg)
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We now have 2 Events
• If user presses the space bar, our
program will execute the jumpOut
method
• What do we do if the user presses a
1?
Events
Summary
1. We have events (user presses space
bar and user types a 1)
2. We have event handlers.
3. We have a Billboard to display
instruction
4. Now, let’s put it all together!
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Putting it All Together
When the World starts:
1. Make everything invisible except the
billboard (instructions).
2. When the user presses a 1, the
world.myfirstmethod should begin
execution.
3. The world.myfirstmethod should make
the billboard invisible and everything
else should be visible.
Practice XIII
Choose 1 of the following:
1. Add instructions for your Practice XI
program. Make sure that your billboard
“is showing=true” but that it changes to
“is showing=false” when the user presses
a particular key.
2. Page AL 224, Three Dancing Penguins
3. Page AL 226, Simple Flight Simulator
1.
Practice VI Test
What is the difference between “interactive” and
“passive” animations?
2.
Interactive animations are created in Alice creating a/an
___________.
3. _________________ run __________________ when
certain things happen like a key is pressed or the mouse
is clicked. on an object.
4. Show the specific instruction that should be used for each
of the following scenarios.
a. We wish to move a penguin when a number is typed on the
keyboard
b. We wish to move a penguin when the mouse is click on
the penguin
c. We wish to allow the mouse to move the penguin
d. We wish the arrow keys to move the penguin.
e. Allow the mouse to control the camera location
5. If we want a custom method called “jump” to be executed
each time the mouse is clicked on a penguin, what must we
do first?
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Review of Variables
A variable is a name for a storage
location in the computer’s memory.
In Algebra:
x=21 (x is called a variable)
In computer science, a variable is a
name for a location in memory.
Variables
• In a programming language, when working
with variables:
– You should create “good” variable names (names
should be meaningful
– use the camelCase naming convention
– camelCase means that multi-word names begin
with a lowercase letter and following words are
in uppercase
– Example: timesToJump,yourAge,yourFirstName
Variables
• You should specify the type: number,
object, string, Boolean (true or false)
• You should give variables a beginning
value
• Example: timesToJump (number),
yourFirstName(string)
Creating and using a
variable in Alice
Example 1: Let’s create a world with a
bunny. Your program should have a
variable called numberHops, set it as
a number and give it the value 5.
Then, create a Alice file that will
allow the bunny to jump 5 times using
the variable numberJumps
Using Variables
1. Click on “create new variable”
2. Name the variable and give a value
3. Bring in loop
structureexpressionsvariable
name
4. Add code to the loop
Using a Variable
Creating and using a
variable in Alice
Example 2: Same problem. However,
this time let’s ask the user how many
times the bunny should jump.
Practice XIII
Choose one of the following:
1) Create an Alice scene which will compute and
display the average of two test grades. (Alice
should ask for data from the user)
2) Create an Alice scene which computes and
displays amount of pay (hours worked * pay
rate)
3) Create an Alice scene which asks for your name
and then prints a welcome message that includes
your name.
4) Create an Alice scene of your own but you must
use variables!
Class Demonstrations
Volunteers????
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Manipulating the Camera
• Create world methods
– Scene1
– Scene2
• Add Objects
• Click “more controls”
• Move camera and drop dummy at camera for each
scene
• At the beginning of each scene, place
“camera set point of view to ….” (dummy1,
dummy2, etc.
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User Input
Example – Ask user to input a name
• Create a new variable – name, string
• Drag variable to editor window and set
valueexpressionname
• Drag world function “ask user for a string”
and place on top of “name”other”What
is your name?”
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Using Random Numbers
Example: Create a world with Alice.
Alice should ask the user for a
number between 1 and 10. The user
will get three choices to guess the
number.
Using Lists
Suppose we wish to work with several
similar objects. (7 penguins, for
example)
We should use a programming
construct called “list” or “array”.
To create a list of 7
penguins
1.
2.
3.
4.
Create a new variable
Select Object
Choose make a List
Add items to the list.