MACROMEDIA FLASH 8-LEARNING ACTIONSCRIPT 2.0 IN FLASH User manual

Learning ActionScript 2.0 in Flash

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Acknowledgments
Project Management: Sheila McGinn
Writing: Jen deHaan; Peter deHaan, Joey Lott
Managing Editor: Rosana Francescato
Lead Editor: Lisa Stanziano
Editing: Linda Adler, Geta Carlson, Evelyn Eldridge, John Hammett, Mary Kraemer, Noreen Maher, Jessie Wood, Anne Szabla
Production Management: Patrice O’Neill, Kristin Conradi, Yuko Yagi
Media Design and Production: Adam Barnett, Aaron Begley, Paul Benkman. John Francis, Geeta Karmarkar, Masayo Noda,
Paul Rangel, Arena Reed, Mario Reynoso
Special thanks to Jody Bleyle, Mary Burger, Lisa Friendly, Stephanie Gowin, Bonnie Loo, Mary Ann Walsh, Erick Vera, the beta
testers, and the entire Flash and Flash Player engineering and QA teams.
First Edition: September 2005
Macromedia, Inc.
601 Townsend St.
San Francisco, CA 94103

3
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Intended audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
System requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Updating Flash XML files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
About the documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Additional resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Chapter 1: What’s New in Flash 8 ActionScript . . . . . . . . . . . . . . 19
New in ActionScript 2.0 and Flash 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Changes to security model for locally installed SWF files. . . . . . . . . . 28
Chapter 2: Writing and Editing ActionScript 2.0 . . . . . . . . . . . . . 31
About ActionScript and events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Organizing ActionScript code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Using the Actions panel and Script window. . . . . . . . . . . . . . . . . . . . . . 35
About the Actions panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
About the Script window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
About coding in the Actions panel and Script window. . . . . . . . . . . . . 38
About Actions panel features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
About behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
About ActionScript publish settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Chapter 3: About ActionScript . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
What is ActionScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
About choosing between ActionScript 1.0 and ActionScript 2.0 . . . 69
Understanding ActionScript and Flash Player . . . . . . . . . . . . . . . . . . . .70
Chapter 4: Data and Data Types. . . . . . . . . . . . . . . . . . . . . . . . . . . 71
About data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
About data types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
About variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Organizing data in objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108
About casting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

4Contents
Chapter 5: Syntax and Language Fundamentals . . . . . . . . . . . . 113
About syntax, statements, and expressions . . . . . . . . . . . . . . . . . . . . . .114
About dot syntax and target paths. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
About language punctuators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
About constants and keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
About statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141
About arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
About operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Chapter 6: Functions and Methods . . . . . . . . . . . . . . . . . . . . . . . 201
About functions and methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Understanding methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222
Chapter 7: Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
About object-oriented programming and Flash . . . . . . . . . . . . . . . . . .226
Writing custom class files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .235
About working with custom classes in an application . . . . . . . . . . . . .238
Example: Writing custom classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263
Example: Using custom class files in Flash . . . . . . . . . . . . . . . . . . . . . .276
Assigning a class to symbols in Flash . . . . . . . . . . . . . . . . . . . . . . . . . . .279
Compiling and exporting classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
Understanding classes and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .283
About top-level and built-in classes . . . . . . . . . . . . . . . . . . . . . . . . . . . .286
About working with built-in classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296
Chapter 8: Inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
About inheritance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
About writing subclasses in Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
Using polymorphism in an application . . . . . . . . . . . . . . . . . . . . . . . . . 308
Chapter 9: Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
About interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
Creating interfaces as data types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Understanding inheritance and interfaces . . . . . . . . . . . . . . . . . . . . . . 320
Example: Using interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
Example: Creating a complex interface . . . . . . . . . . . . . . . . . . . . . . . . .323

Contents 5
Chapter 10: Handling Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Using event handler methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
Using event listeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
Using event listeners with components . . . . . . . . . . . . . . . . . . . . . . . . . 335
Using button and movie clip event handlers. . . . . . . . . . . . . . . . . . . . . 337
Broadcasting events from component instances . . . . . . . . . . . . . . . . 342
Creating movie clips with button states. . . . . . . . . . . . . . . . . . . . . . . . . 342
Event handler scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
Scope of the this keyword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
Using the Delegate class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
Chapter 11: Working with Movie Clips. . . . . . . . . . . . . . . . . . . . . . 351
About controlling movie clips with ActionScript . . . . . . . . . . . . . . . . . 352
Calling multiple methods on a single movie clip . . . . . . . . . . . . . . . . . 354
Loading and unloading SWF files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
Changing movie clip position and appearance . . . . . . . . . . . . . . . . . . 357
Dragging movie clips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
Creating movie clips at runtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
Adding parameters to dynamically created movie clips. . . . . . . . . . . 364
Managing movie clip depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
About caching and scrolling movie clips with ActionScript . . . . . . . 369
Using movie clips as masks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
Handling movie clip events. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
Assigning a class to a movie clip symbol. . . . . . . . . . . . . . . . . . . . . . . . 378
Initializing class properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
Chapter 12: Working with Text and Strings . . . . . . . . . . . . . . . . . 381
About text fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383
About loading text and variables into text fields . . . . . . . . . . . . . . . . . 392
Using fonts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398
About font rendering and anti-alias text . . . . . . . . . . . . . . . . . . . . . . . . 406
About text layout and formatting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .414
Formatting text with Cascading Style Sheet styles . . . . . . . . . . . . . . .421
Using HTML-formatted text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 436
Example: Creating scrolling text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449
About strings and the String class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 450

6Contents
Chapter 13: Animation, Filters, and Drawings. . . . . . . . . . . . . . 469
Scripting animation with ActionScript 2.0 . . . . . . . . . . . . . . . . . . . . . .470
About bitmap caching, scrolling, and performance . . . . . . . . . . . . . 480
About the Tween and TransitionManager classes . . . . . . . . . . . . . . . 481
Using filter effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 498
Working with filters using ActionScript . . . . . . . . . . . . . . . . . . . . . . . . 505
Manipulating filter effects with code . . . . . . . . . . . . . . . . . . . . . . . . . . . 530
Creating bitmaps with the BitmapData class . . . . . . . . . . . . . . . . . . . .534
About blending modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .537
About operation order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
Drawing with ActionScript. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 540
Understanding scaling and slice guides . . . . . . . . . . . . . . . . . . . . . . . . .556
Chapter 14: Creating Interaction with ActionScript . . . . . . . . . . 561
About events and interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .562
Controlling SWF file playback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .562
Creating interactivity and visual effects . . . . . . . . . . . . . . . . . . . . . . . . .566
Creating runtime data bindings using ActionScript . . . . . . . . . . . . . . .579
Deconstructing a sample script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .588
Chapter 15: Working with Images, Sound, and Video . . . . . . . . 591
About loading and working with external media . . . . . . . . . . . . . . . . 592
Loading external SWF and image files. . . . . . . . . . . . . . . . . . . . . . . . . 593
About loading and using external MP3 files . . . . . . . . . . . . . . . . . . . . .598
Assigning linkage to assets in the library . . . . . . . . . . . . . . . . . . . . . . . 602
About using FLV video. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
About creating progress animations for media files. . . . . . . . . . . . . . .624
Chapter 16: Working with External Data . . . . . . . . . . . . . . . . . . 633
Sending and loading variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .634
Using HTTP to connect to server-side scripts . . . . . . . . . . . . . . . . . . .638
About file uploading and downloading . . . . . . . . . . . . . . . . . . . . . . . . . 644
About XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .652
Sending messages to and from Flash Player . . . . . . . . . . . . . . . . . . . .663
About the External API . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .667
Chapter 17: Understanding Security. . . . . . . . . . . . . . . . . . . . . . .677
About compatibility with previous Flash Player security models . . . 677
About local file security and Flash Player. . . . . . . . . . . . . . . . . . . . . . . .679
About domains, cross-domain security, and SWF files . . . . . . . . . . 694
Server-side policy files for permitting access to data . . . . . . . . . . . . .702
HTTP to HTTPS protocol access between SWF files . . . . . . . . . . . . 707

Contents 7
Chapter 18: Debugging Applications . . . . . . . . . . . . . . . . . . . . . . 711
Debugging your scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 711
Using the Output panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724
Chapter 19: Best Practices and Coding Conventions for
ActionScript 2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 731
Naming conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 732
Using comments in your code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 742
ActionScript coding conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 745
ActionScript and Flash Player optimization . . . . . . . . . . . . . . . . . . . . . 762
Formatting ActionScript syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764
Appendix A: Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . .773
Appendix B: Deprecated Flash 4 operators . . . . . . . . . . . . . . . 779
Appendix C: Keyboard Keys and Key Code Values . . . . . . . . . . 781
Appendix D: Writing Scripts for
Earlier Versions of Flash Player . . . . . . . . . . . . . . . . . . . . . . . . . . .787
About targeting earlier versions of Flash Player . . . . . . . . . . . . . . . . . 787
Using Flash 8 to create content for Flash Player 4 . . . . . . . . . . . . . . 788
Appendix E: Object-Oriented Programming with
ActionScript 1.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791
About ActionScript 1.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 792
Creating a custom object in ActionScript 1.0 . . . . . . . . . . . . . . . . . . . . 794
Assigning methods to a custom object in ActionScript 1.0. . . . . . . . 795
Defining event handler methods in ActionScript 1.0 . . . . . . . . . . . . . 796
Creating inheritance in ActionScript 1.0 . . . . . . . . . . . . . . . . . . . . . . . . 798
Adding getter/setter properties to objects in ActionScript 1.0. . . . . 800
Using Function object properties in ActionScript 1.0 . . . . . . . . . . . . . .801
Appendix F: Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 811

8Contents

9
Introduction
Macromedia Flash Basic 8 and Macromedia Flash Professional 8 are the professional standard
authoring tools for producing high-impact web experiences. ActionScript is the language you
use to add interactivity to Flash applications, whether your applications are simple animated
SWF files or more complex rich Internet applications. You don’t have to use ActionScript to
use Flash, but if you want to provide basic or complex user interactivity, work with objects
other than those built into Flash (such as buttons and movie clips), or otherwise turn a SWF
file into a more robust user experience, you’ll probably want to use ActionScript.
For more information, see the following topics:
Intended audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Updating Flash XML files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
System requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
About the documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Additional resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Intended audience
This manual assumes that you have already installed Flash Basic 8 or Flash Professional 8 and
know how to use the user interface.You should know how to place objects on the Stage and
manipulate them in the Flash authoring environment. If you have used a scripting language
before, ActionScript will seem familiar. But if you’re new to programming, ActionScript basics
are easy to learn. You can start with simple commands and build more complexity as you
progress. You can add a lot of interactivity to your files without having to learn (or write) a lot
of code.

10 Introduction
System requirements
ActionScript 2.0 does not have any system requirements in addition to Flash 8.
This manual assumes that you are using the default publishing settings for your Flash files:
Flash Player 8 and ActionScript 2.0. If you change either of these settings, explanations and
code samples in the documentation might not work correctly. If you develop applications for
earlier versions of Flash Player, see Appendix D, “Writing Scripts for Earlier Versions of Flash
Player,” on page 787.
Updating Flash XML files
It is important that you always have the latest Flash XML files installed. Macromedia
sometimes introduces features in dot releases (minor releases) of Flash Player. When such a
release is available, you should update your version of Flash to get the latest XML files.
Otherwise, the Flash 8 compiler might generate errors if you use new properties or methods
that were unavailable in the version of Flash Player that came with your Flash installation.
For example, Flash Player 7 (7.0.19.0) contained a new method for the System object,
System.security.loadPolicyFile. To access this method, you must use the Player
Updater installer to update all the Flash players that are installed with Flash. Otherwise, the
Flash compiler displays errors.
Remember that you can install a Player Updater that is one or more major versions ahead of
your version of Flash. By doing this, you will get the XML files that you need but shouldn’t
have any compiler errors when you publish to older versions of Flash Player. Sometimes new
methods or properties are available to older versions, and having the latest XML files
minimizes the compiler errors you get when you try to access older methods or properties.
About the documentation
This manual provides an overview of ActionScript syntax and information on how to use
ActionScript when working with different types of objects. For details on the syntax and usage
of every language element, see the ActionScript 2.0 Language Reference.
For more information, see the following topics:
■“Learning ActionScript 2.0 book overview” on page 11
■“About the sample files” on page 14
■“Terms used in this document” on page 13
■“Copy and paste code” on page 13