ActionScript

A Primer


Based on JavaScript



Object
-
oriented programming



Everything you do in
ActionScript

does something to some
object*



Some objects in Flash


Movie Clip


Graphic


Button



Objects are defined by classes in AS3

2

*
anything you can manipulate in some way


Class
: a group of items that are similar in some way


Items are called
objects

or
instances

of the class

▪
Objects

can be concrete (like a
button

or
graphic
) or abstract (like a
variable

that is invisible, but hold data)

▪
Objects have two aspects: form (
properties
) and function
(
methods
)



Each
property

and
method

is defined by
Actions
(pieces of code that tell Flash how to manipulate a
target object at any point in your movie).

3


Ball could be considered a
class

of items defined as
“spherical things”


One
object

in this
class

is a movie clip called
Tennis_ball

▪
The
properties

of
Tennis_ball

might be the color
neon green

or a 20
-
pixel diameter

▪
Its
methods

might be bounce, roll, and/or spin


A 2
nd

object

in the ball
class

might be Softball

▪
Properties

white…etc.


4


syntax


variables


constants


statements


assignment statements


keywords


operators


expressions


arrays


procedures


functions


arguments


control structures


loops


conditions


comments

5


control
the
playhead

of a timeline


move
things around


create
and manage user interfaces


play
sounds


control
video


manage
data (xml, lists,
etc
)


communicate
with server
-
side applications (e.g., web
servers)


6


select frame 1


type the following into the
Actions
panel
:



var

message
= "Hello world!";


that line of code constitutes a complete instruction, known
as a
statement



now create three more statements:

var

firstName

= "
your name here
";

trace(message
);

trace ("
Hi there, " +
firstName

+ ", nice to meet you
.");



play
the
movie
-

select
Control
>>
Test Movie


7


ActionScript

notation must end in ;


object.method

(argument);


like
noun.verb

(adjective);



Example 1

root.gotoAndPlay
(2);

this.gotoAndPlay
(2);

gotoAndPlay
(2);



Explanation: This script instructs the
playhead

on the main timeline
(“root” or “this”) to go to and play on frame 2. Identifying “root” or “this”
by name is optional
—
the current timeline is the default, so you could just
say
gotoAndPlay
(2);


8


To write AS on Timeline:

1.
Click on a
key frame

and then press F9.

2.


9

Methods:


play();


stop();


gotoAndPlay
();


gotoAndStop
();


nextFrame
();


prevFrame
();


navigateToURL
();


Properties


currentFrame


currentLabel


currentLabels


totalFrames

10


Reusable content stored in Library


Create
instance

from symbols, and name


Make a pictures slideshow
(SlideShow.fla)

12

1.
Open a Flash file (AS3.0)

2.
Import
pics

to library (File
-
>Import)

3.
Convert the
pics

to Movie Clip
(Optional)


4.
Make
keyframes

and place a pic to every
Keyframe

13

5.
Create a button symbol and put it in a new layer

6.
Make two instances (next,
prev
) from the button
symbol

7.
Give an instance name “
nextButton
” and another one
“
previousButton
”



14


Create a new layer and name it, say, “AS3”


Write code on the
keyframe

of the AS3 layer




15

1.
stop();


2.
nextButton.
addEventListener
(
MouseEvent.CLICK
,
onNextButtonClicked
);


3.
previousButton.
addEventListener
(
MouseEvent.CLICK
,
onPreviousButtonClicked
);


4.
function

onNextButtonClicked
(
e:
MouseEvent
):
void

{

5.

if (
currentFrame

==
totalFrames
) {

6.


gotoAndStop
(1);

7.

} else {

8.


nextFrame
();

9.

}

10.
}


11.
function

onPreviousButtonClicked
(
e:
MouseEvent
):void {

12.

if (
currentFrame

== 1) {

13.


gotoAndStop
(
totalFrames
);

14.

} else {

15.


prevFrame
();

16.

}

17.
}

16

1.
stop();



2.
// add an event listener to the next button

3.
nextButton.
addEventListener
(
MouseEvent.CLICK
,
onNextButtonClicked
);


4.
// add an event listener to the previous button

5.
previousButton.
addEventListener
(
MouseEvent.CLICK
,
onPreviousButtonClicked
);


6.
// a function that goes to the next frame when the next button is clicked

7.
function

onNextButtonClicked
(
e:
MouseEvent
):
void

{

8.

if (
currentFrame

==
totalFrames
) {

9.


gotoAndStop
(1);

10.

} else {

11.


nextFrame
();

12.

}

13.
}


14.
// a function that goes to the previous frame when the next button is clicked

15.
function

onPreviousButtonClicked
(
e:
MouseEvent
):void {

16.

if (
currentFrame

== 1) {

17.


gotoAndStop
(
totalFrames
);

18.

} else {

19.


prevFrame
();

20.

}

21.
}

17