alice-teacher Event Listeners and Handle Active Command in Alice 3.1

[Scott Hogben]

Hi Don,

 

There seems to be a lot of info in regards to Alice but it is tough to make
heads or tails or to even figure out where things begin.  I would be
interested in using Alice in the classroom but I have zero idea where to
begin or how to use it.  Is there a curriculum or lessons?  Thank you!

 

SCOTT HOGBEN

 

From: alice-teachers-bounces+srhogben=comcast.net at lists.andrew.cmu.edu
[mailto:alice-teachers-bounces+srhogben=comcast.net at lists.andrew.cmu.edu] On
Behalf Of Don Slater
Sent: Wednesday, October 01, 2014 12:51 PM
To: Alice Teachers
Subject: Re: alice-teacher Event Listeners and Handle Active Command in
Alice 3.1

 

See below...

 

On Oct 1, 2014, at 9:39 AM, Emily Higgins <erphiggins at gmail.com> wrote:





Dear All-

 I have two questions. 

1)  What does the Handle Active command do in Alice 3.1?

 

I assume you mean the HandleActiveChanged method of the Scene class. This is
a method that will facilitate the creation of multiple scenes in Alice 3
when it is implemented. If you look at what it does right now (see attached
screen shot), you will see that it essentially builds the current (and only
possible) Scene, readying it for execution. It is not a method you or your
students need to use at this time.

 

2) How can you set up a program so that an object is only affected by an
event listener for part of the program?  For example, a student wants to
have the program user move a box but only at a certain point of the program.
I can't figure out how to limit when an event listener is active.  

 

The student should create a boolean variable for the Scene class that is
initially set to false as the program runs, and at the time when the student
wants the event to become active, he sets the value of the variable to true.
He would reset it to false when he no longer wants to listen for the event.

 

Then the event would be guarded by an if statement, that performs the event
action when the variable is true.

 

For example, i have a type of "Whack-A-Mole" game in which the player is
supposed to click on the target object when it appears, but you only one to
add one point at most for each appearance of the target.

 

So my code might look something like

 

            Scene variable / property -> boolean isClickedOn = false;

 

            Event definition - mouseClickListener

 

                        if (mouse clicks on target) and (not isClickedOn)

                                    add 1 to score

                                    isClickedOn = true

 

            target move method

                        hide target

                        if (isClickedOn)

                                    isClickedOn = false

                        move target

                        showTarget

 

 

            myFirstMethod

                        while (score < targetScore) or (time runs out)

                                    target move

                        game over

 

Let me know if you have any other questions.

 

All the best,

 

 



 

Don Slater

Alice Team

Carnegie Mellon University

5000 Forbes Avenue

Pittsburgh, PA 15213

 

Email: don at alice.org

 

I have learned this at least by my experiment: that if one advances
confidently in the direction of his dreams, and endeavors to live the life
he has imagined, he will meet with a success unexpected in common hours.
--- Henry David Thoreau

 

The true object of all human life is play. -- G.K. Chesterton

 

Thank you,

Emily Higgins

Boothbay Region High School

Boothbay Harbor, Maine

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