code by Michael Avila,
written by Kirupa | 3 April 2006
In the previous
page, you learned how to specify key combinations.
But that is only part of the fun. We need to specify what
needs to be done when a certain key combination is pressed.
For that, we look at the switch statement in the code:
- switch
(name)
{
- case
"caseName1"
:
- //something
- break;
- case
"caseName2"
:
- //something
- break;
- }
Replace caseName1 and caseName2 with
the caseName value you specified in your addCombination
arguments. When a key combination is executed, the
appropriate switch case will be fired. Any code that is
contained in that particular case will be executed. One
thing to remember, though, is that you will need a
separate case for every key combination you specify.
While in the above example I only provided two cases,
you can have as many cases as you want. Just remember to
give your caseName values a unique name, or else Flash
won't know which case to fire.
For the most part, the code you need to use the key
detection is straightforward. I want to take a big
u-turn and talk about the actual code in the
KeyDetection class file. For, I think that is where the
real action is!
Code Explained
Learning how to use the code is just one part of this
tutorial. The other major part involves learning why the
code works. Let's start at the top of our
KeyDetection.as file:
- // a list of all the key codes
that have been pressed
- private
var
keys_pressed :
Array;
- // a multi-dimensional list of
all of our key combinations
- private
var
key_combinations :
Array;
- // objects listening to this
detection
- private
var
listeners :
Array;
The keyDetection class contains three private variables,
keys_pressed, key_combination, and listeners, that will be
instantiated for each object created.
- public
function
KeyDetection
()
- {
- keys_pressed
=
new Array
();
- key_combinations
=
new Array
();
- listeners
=
new Array
();
- // allow this object to
listen for events from the key object
- Key.addListener
(this);
- }
The above code is the constructor used to create
KeyDetection objects. The constructor basically creates the
object. Very little heavy lifting goes on here. The main
thing to note is that the private variables we declared
earlier are initialized here, and that ensures that a local
copy of these variables are attached to the object being
created by the constructor.
In the last line, I add this object to the Key's
addListener method. The this variable inside the
constructor refers to the object being created by this
constructor.
- public
function
addListener
(listener
:
Object)
: Void
- {
- for
(var
i
: Number
=
0; i
<
listeners.length;
i
++)
- {
- if
(listeners
[i]
==
listener)
return;
- }
- listeners.push
(listener);
- }
If your listeners array does not contain the object being
passed in, then you add this object to your listeners array.
This method is called by your Key.addListener line in the
constructor.
We have barely scratched the surface of the code. There
is more on the next
page!
|
Multiple Key Detection - Page 3
