Tài liệu Thiết kế flash với flash cs5 part 56 docx

For example, _root.amer-ica.kansas.wichita defines a movie clip on the main _root Timeline with the name america, containing a movie clip named kansas, which in turn contains a movie c

ActionScript, just like any human language,

has rules you should follow However, in

ActionScripts, you have to follow the rules or

it won't work One of the more important

rules to follow is the use of dot syntax The

use of dots (.) in a script serves several

pur-poses First, is to specify the target path to a

particular Timeline For example,

_root.amer-ica.kansas.wichita defines a movie clip on the

main (_root) Timeline with the name america,

containing a movie clip named kansas, which

in turn contains a movie clip named wichita

Dot syntax is used to create a road map for

Flash to follow Dot syntax is a separator

between two or more parts of a Flash script

Another use of dot syntax is to change the properties and methods for a specific object

Since ActionScript, by definition is an object-oriented language, Flash performs its respon-sibilities by instructing an object to do something (method), or by changing a

prop-erty For example, star._rotation = 90; instructs

Flash to rotate the MovieClip instance named star, 90 degrees (property) To instruct the star MovieClip instance to play (method), you

would enter the following code: star.play();

Using Dot Syntax

Movie Clip with Instance Name: MovieA

ActionScript 2.0

When you use ActionScripts, you have the

ability to work with data Data can be

informa-tion entered in by a visitor in an input data

field, or it can be computer information such

as the current position of the mouse, or the

date and time When you work with data, you

have 4 possible data types:

◆ String Allows for the entering of text

values

◆ Number Allows for the entering of

numeric values

◆ Boolean A Boolean state has two

values; typically true or false

◆ Object Serves as a storage device for

any data type, including other objects

Use Data Types to Control Information

Since data types control the type of

informa-tion that can be entered into a data field, you

can use them to validate the data someone is

entering For example, you want to create a

calculator to convert between degrees

Fahrenheit and Celsius To do this, you will

need an input field for someone to enter the

current temperature in Fahrenheit, a button that would perform the calculation, and then a dynamic text field for the result, and one for

an error message

Select the Input Field, and then give it a unique variable name in the Properties panel

Select the Error Dynamic Text Field and give it a unique variable name in the Properties panel

Select the Results Dynamic Text Field, and give it a unique variable name in the Properties panel

Select the button instance, and then enter a script into the Actions panel (see the example file for script details)

When the movie is played, the visitor will enter a value into the data field, and it will be evaluated as to whether it's purely numeric If

it isn't, an error message will display in the dynamic error field If the field contains num-bers, then the calculation will perform the conversion and display the results displayed

in the output field

4 3 2 1 Understanding Data Types

Error Message using text Error Message using a

blank field

Correct data no error message

A function is a block of ActionScript code that

can be reused anywhere in a SWF file If you

pass values as parameters to a function, the

function will operate on those values A

func-tion can also return values Flash contains

built-in functions that let you access certain

information and perform certain tasks, such

as getting the version number of Flash Player

hosting the SWF file (getVersion()) Functions

that belong to an object are called methods

Functions that don't belong to an object are

called top-level functions and are found in the

Functions category of the Actions panel

Each function has its own characteristics,

and some functions require you to pass

cer-tain values If you pass more parameters than

the function requires, the extra values are

ignored If you don't pass a required

parame-ter, the empty parameters are assigned the

undefined data type, which can cause errors

when you export a script To call a function, it

must be in a frame that the playhead has

reached

To call a function, simply use the function

name and pass any required parameters The

following code describes a common syntax

for creating functions:

function firstFunction (x, y, z) {

// place all actions here;

}

Using Functions

Calling a Function

Functions begin with the word function, fol-lowed by the name of the function (user-defined) The area enclosed by parenthesis is used for passing parameters to the function actions If the parameters are left blank, you're essentially creating a generic function that will function the same way every time it's called If the function contains parameters, it will perform in a unique way each time it's called When you call a function, you're instructing Flash to execute all of the actions within that function Therefore, if firstFunction contained 20 actions, all of them would be executed by using a single line of script To call a function, simply add this line to the action:

myFunction ();

Passing Parameters to a Function

If the function has been defined to accept parameter information, you can use the fol-lowing line of script:

myFunction (parameter 1, parameter2);

Once a Function is defined, it can be called anytime it's needed Therefore, it's a good practice to define all of your functions in frame 1 of the active Flash document That way they can be called anytime after that

Conditional statements in ActionScript are a

critical part of interactivity They let you

pro-gram a script based on any number of

condi-tions For example, in the morning, you say

good day, or good morning to someone you

meet In doing so, you made a conditional

choice

ActionScript does the same thing You can

create an ActionScript that checks the time of

day If it's before noon, Flash responds with a

Good Morning message If it's from noon to 5,

Flash says Good Afternoon, or from 5 till

mid-night, Flash says Good Evening This type of

condition is known as an if/else condition If

this happens, do this… else do that Since a

variable can be almost anything you can

measure on a computer, and a conditional

statement is made up of two or more

vari-ables, ActionScript can be taken to a point

where it almost thinks for itself The previous

example could be expressed in flow charting

the following way:

Typically, when you're creating a condi-tional statement, you're comparing one ele-ment against another using operators The following operators are available to create conditional statements:

◆ == Checks for equality between two values (is time of day equal to 5)

◆ != Checks for inequality between two values

◆ < Checks for less than (is value A less than value B)

◆ > Checks for greater than (is value A greater than value B)

◆ <= Checks for less than or equal to between two values

◆ >= Checks for greater than or equal to between two values

◆ && Checks for a logical AND (if day ==

"Friday" && time > 5)

◆ || Checks for a logical OR (if day ==

"Saturday" || day == "Sunday")

Using these operators to check between two or more values, you can create complex ActionScripts that react differently based on the available data To create a dynamic field that checks the time, and responds with the appropriate answer, you would enter the fol-lowing code:

if (time > "0000 && time < 1200) { response = "Good Morning";

} else if (time >1200 && time < 1700) { response = "Good Afternoon";

}else if (time > 1700 && time < 2400);

Using Conditional Statements

Attaching a mouse event to a button is probably the easiest of all the event handlers For example, you have a movie clip of a dog that con-tains a barking audio file When the movie clip plays, the dog barks The trick is to have the dog bark when the visitor rolls their mouse over the dog’s face To do this, you will need to create an invisible button and then attach the mouse event to the invisible button

Attaching a Mouse

Event to a Button

Attach an Event to a Button

Click the Insert menu, and then

click New Symbol.

Select the Button type, and then

name the symbol

Click OK.

Create a blank keyframe in the Hit

state of the button, and then

create a shape

Leave the Up, Over, and Down

states blank

Exit the Symbol editing mode, and

then return to the Stage

Drag a movie clip onto the Stage

Create a new layer, and then name

the layer

Drag the invisible button onto the

Stage, and then place it over the

area of the image you want to use

as a button

Enter the script (ActionScript 2.0)

as shown in the illustration

◆ ActionScript 3.0 example files

are available on the Web at

www.perspection.com

When the visitor rolls into or out of

the invisible button, the rollOver or

rollOut event handlers will trigger

the playing or stopping of the dog

movie clip

Click the Control menu, point to

Test Movie, and then click Test.

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Frame event handlers are easy to understand When an action is attached to a frame, the action is triggered when the play head hits the frame For example, you want to create a frame event that swaps images on the Stage, and you want the images to swap every 40 frames You can attach an ActionScript that swaps the image, and place the action every 40 frames When the play head hits the frame, the action executes When you attach an ActionScript to a frame, you’ll need a blank keyframe on the Timeline, and it is strongly recommended that you always place ActionScripts in a separate layer from access and control In addition, if you're planning to swap images in a Flash movie, it's always best to use a blank movie clip (called a placeholder)

to hold the images

Working with

Frame Events

Attach an ActionScript

to a Frame

Drag a blank movie clip onto the

Stage, and then select the clip

Give the movie clip a unique

instance name in the Properties

panel

Create a new layer, and then name

the layer

Create blank keyframes at frame

numbers 1, 21, 41, and 61

Select a frame, click the Insert

menu, point to Timeline, and then

click Blank Keyframe.

Select frame 1, and then enter the

script (ActionScript 2.0) as shown

in the illustration

◆ ActionScript 3.0 example files

are available on the Web at

www.perspection.com

Select frames 21, 41, and 61, and

then repeat the script, except

change the name of the image you

want to load (image_b.jpg,

image_c.jpg, image_d.jpg)

Click the Control menu, point to

Test Movie, and then click Test.

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