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

[Emily Higgins]

Don -
Could you send a screenshot of how you would program what you did the
algorithm for Whack-A-Mole?  I can't figure out where to put the
isClickedOn variable.

Refresher - the question was how to control when an event listener is
activated, and the response was this:
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


Thank you
Emily Higgins

On Wed, Oct 1, 2014 at 12:51 PM, Don Slater <dslater at andrew.cmu.edu> wrote:

> 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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