Macromedia Flash ActionScript - MX 2004 Reference Guide

ActionScript Reference Guide

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Add Life to the Web, Afterburner, Aftershock, Andromedia, Allaire, Animation PowerPack, Aria, Attain, Authorware, Authorware Star, Backstage, Bright Tiger, Clustercats, ColdFusion, Contribute, Design In Motion, Director, Dream Templates, Dreamweaver, Drumbeat 2000, EDJE, EJIPT, Extreme 3D, Fireworks, Flash, Fontographer, FreeHand, Generator, HomeSite, JFusion, JRun, Kawa, Know Your Site, Knowledge Objects, Knowledge Stream, Knowledge Track, LikeMinds, Lingo, Live Effects, MacRecorder Logo and Design, Macromedia, Macromedia Action!, Macromedia Flash, Macromedia M Logo and Design, Macromedia Spectra, Macromedia xRes Logo and Design, MacroModel, Made with Macromedia, Made with Macromedia Logo and Design, MAGIC Logo and Design, Mediamaker, Movie Critic, Open Sesame!, Roundtrip, Roundtrip HTML, Shockwave, Sitespring, SoundEdit, Titlemaker, UltraDev, Web Design 101, what the web can be, and Xtra are either registered trademarks or trademarks of Macromedia, Inc. and may be registered in the United States or in other jurisdictions including internationally. Other product names, logos, designs, titles, words, or phrases mentioned within this publication may be trademarks, service marks, or trade names of Macromedia, Inc. or other entities and may be registered in certain jurisdictions including internationally.

Third-Party Information

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Apple Disclaimer

APPLE COMPUTER, INC. MAKES NO WARRANTIES, EITHER EXPRESS OR IMPLIED, REGARDING THE ENCLOSED COMPUTER SOFTWARE PACKAGE, ITS MERCHANTABILITY OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. THE EXCLUSION OF IMPLIED WARRANTIES IS NOT PERMITTED BY SOME STATES. THE ABOVE EXCLUSION MAY NOT APPLY TO YOU. THIS WARRANTY PROVIDES YOU WITH SPECIFIC LEGAL RIGHTS. THERE MAY BE OTHER RIGHTS THAT YOU MAY HAVE WHICH VARY FROM STATE TO STATE.

Copyright © 2003 Macromedia, Inc. All rights reserved. This manual may not be copied, photocopied, reproduced, translated, or converted to any electronic or machine-readable form in whole or in part without prior written approval of Macromedia, Inc. Part Number ZFL70M400

Acknowledgments

Director: Erick Vera

Project Management: Stephanie Gowin, Barbara Nelson

Writing: Jody Bleyle, Mary Burger, Kim Diezel, Stephanie Gowin, Dan Harris, Barbara Herbert, Barbara Nelson, Shirley Ong, Tim Statler

Managing Editor: Rosana Francescato

Editing: Linda Adler, Mary Ferguson, Mary Kraemer, Noreen Maher, Antonio Padial, Lisa Stanziano, Anne Szabla

Production Management: Patrice O’Neill

Media Design and Production: Adam Barnett, Christopher Basmajian, Aaron Begley, John Francis, Jeff Harmon

First Edition: Septermber 2003

Macromedia, Inc. 600 Townsend St. San Francisco, CA 94103

INTRODUCTION: Getting Started with ActionScript . . . . . . . . . . . . . . . . . . . . . . . 9

Intended audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

System requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Using the documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Typographical conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Terms used in this document. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Additional resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

PART I: Welcome to ActionScript

CHAPTER 1: What’s New in Flash MX 2004 ActionScript. . . . . . . . . . . . . . . . . . 13

New and changed language elements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

New security model and legacy SWF files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Porting existing scripts to Flash Player 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

ActionScript editor changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Debugging changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

New object-oriented programming model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

CHAPTER 2: ActionScript Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Differences between ActionScript and JavaScript . . . . . . . . . . . . . . . . . . . . . . . . . 25

Unicode support for ActionScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

About data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Assigning data types to elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

About variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

Using operators to manipulate values in expressions . . . . . . . . . . . . . . . . . . . . . . . 45

Specifying an object’s path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Using built-in functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Creating functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

CHAPTER 3: Writing and Debugging Scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Controlling when ActionScript runs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Using the Actions panel and Script window. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Using the ActionScript editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

Debugging your scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

Using the Output panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Updating Flash Player for testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

PART II: Handling Events and Creating Interaction

CHAPTER 4: Handling Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Using event handler methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Using event listeners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Using button and movie clip event handlers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

Creating movie clips with button states . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Event handler scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Scope of the “this” keyword. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

CHAPTER 5: Creating Interaction with ActionScript . . . . . . . . . . . . . . . . . . . . . . 91

About events and interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Controlling SWF file playback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Creating interactivity and visual effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

Deconstructing a sample script . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

PART III: Working with Objects and Classes

CHAPTER 6: Using the Built-In Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

About classes and instances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

Overview of built-in classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

CHAPTER 7: Working with Movie Clips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

About controlling movie clips with ActionScript . . . . . . . . . . . . . . . . . . . . . . . . . 121

Calling multiple methods on a single movie clip . . . . . . . . . . . . . . . . . . . . . . . . . 122

Loading and unloading additional SWF files. . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Specifying a root Timeline for loaded SWF files . . . . . . . . . . . . . . . . . . . . . . . . . 123

Loading JPEG files into movie clips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

Changing movie clip position and appearance. . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Dragging movie clips. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Creating movie clips at runtime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Adding parameters to dynamically created movie clips . . . . . . . . . . . . . . . . . . . . 128

Managing movie clip depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

Drawing shapes with ActionScript. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

Using movie clips as masks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

4 Contents

Handling movie clip events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

Assigning a class to a movie clip symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

Initializing class properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

CHAPTER 8: Working with Text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Using the TextField class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

Creating text fields at runtime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

Using the TextFormat class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

Formatting text with Cascading Style Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

Using HTML-formatted text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

Creating scrolling text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

CHAPTER 9: Creating Classes with ActionScript 2.0 . . . . . . . . . . . . . . . . . . . . 155

Principles of object-oriented programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

Using classes: a simple example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

Creating and using classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

Instance and class members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

Creating and using interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

Understanding the classpath . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

Using packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Importing classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

Implicit get/set methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

Creating dynamic classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

How classes are compiled and exported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

PART IV: Working with External Data and Media

CHAPTER 10: Working with External Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Sending and loading variables to and from a remote source. . . . . . . . . . . . . . . . . 177

Sending messages to and from Flash Player . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

Flash Player security features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

CHAPTER 11: Working with External Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Overview of loading external media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

Loading external SWF and JPEG files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

Loading external MP3 files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

Reading ID3 tags in MP3 files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

Playing back external FLV files dynamically . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

Preloading external media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198

Contents 5

PART V: Reference

CHAPTER 12: ActionScript Dictionary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

Sample entry for most ActionScript elements . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

Sample entry for classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Contents of the dictionary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

Accessibility class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266

Arguments class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272

Array class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273

Boolean class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289

Button class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293

Camera class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312

Color class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

ContextMenu class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335

ContextMenuItem class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341

CustomActions class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347

Date class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349

Error class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377

Function class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389

Key class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

LoadVars class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425

LocalConnection class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 434

Math class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 445

Microphone class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461

Mouse class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 476

MovieClip class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482

MovieClipLoader class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544

NetConnection class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555

NetStream class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 556

Number class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 569

Object class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574

PrintJob class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 595

Selection class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607

SharedObject class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617

Sound class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624

Stage class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 640

String class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

System class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 661

System.capabilities object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 666

System.security object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 675

TextField class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 680

TextField.StyleSheet class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703

TextFormat class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715

TextSnapshot object . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725

Video class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 744

XML class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 751

XMLNode class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 773

XMLSocket class . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 774

6 Contents

APPENDIX A: Error Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 783

APPENDIX B: Operator Precedence and Associativity . . . . . . . . . . . . . . . . . . . 787

APPENDIX C: Keyboard Keys and Key Code Values . . . . . . . . . . . . . . . . . . . . . 789

Letters A to Z and standard numbers 0 to 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 789

Keys on the numeric keypad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 790

Function keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 791

Other keys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 792

APPENDIX D: Writing Scripts for Earlier Versions of Flash Player. . . . . . . . . . . 795

About targeting older versions of Flash Player . . . . . . . . . . . . . . . . . . . . . . . . . . . 795

Using Flash MX 2004 to create content for Flash Player 4. . . . . . . . . . . . . . . . . . 796

APPENDIX E: Object-Oriented Programming with ActionScript 1 . . . . . . . . . . . 799

About ActionScript 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 799

INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 807

Contents 7

8 Contents

INTRODUCTION

Getting Started with ActionScript

Macromedia Flash MX 2004 and Flash MX Professional 2004 are the professional standard authoring tools for producing high-impact web experiences. ActionScript is the language you use when you want to develop an application within Flash. You don’t have to use ActionScript to use Flash, but if you want to provide 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.

Intended audience

This book assumes that you already have Flash MX 2004 or Flash MX Professional 2004 installed and know how to use it. You should know how to place objects on the Stage and manipulate them in the Flash authoring environment. If you have written programs before, ActionScript will feel familiar. But even if you haven’t, ActionScript isn’t hard to learn. It’s easy to start with very simple commands and build more complexity as you go along.

System requirements

ActionScript does not have any system requirements in addition to Flash MX 2004 or Flash MX Professional 2004. However, the documentation assumes that you are using the default publishing settings for your Flash files: Flash Player 7 and ActionScript 2.0. If you change either of these settings, explanations and code samples shown in the documentation may not work correctly.

Using the documentation

This document provides an overview of ActionScript syntax, information on how to use ActionScript when working with different types of objects, and details on the syntax and usage of every language element. Start by learning the terminology and basic concepts used in the rest of the document (see Chapter 2, “ActionScript Basics,” on page 25). Next, learn the mechanics of writing and debugging Flash scripts (see Chapter 3, “Writing and Debugging Scripts,”

on page 55).

Before writing your own scripts, you should complete the lessons “Write Scripts with ActionScript” and “Create a Form with Conditional Logic and Send Data,” which provide a hands-on introduction to working with ActionScript. To find these lessons, select Help > How Do I > Quick Tasks.

After you understand the basics, you are ready to use the information in the rest of this document as it applies to the specific effect you are trying to achieve. For example, if you want to learn how to write a script that performs a certain action when a user clicks the mouse, see Chapter 4,

“Handling Events,” on page 83.

When you find information about a certain command you want to use, you can look up its entry in Chapter 12, “ActionScript Dictionary,” on page 205; every language element is listed there in alphabetical order.

Typographical conventions

The following typographical conventions are used in this book:

• Code font indicates ActionScript code.

• Code font italic indicates an element, such as an ActionScript parameter or object name,

that you replace with your own text when writing a script.

Terms used in this document

The following terms are used in this book:

• You refers to the developer who is writing a script or application.

• The user refers to the person who will be running your scripts and applications.

• Compile time is the time at which you publish, export, test, or debug your document.

• Runtime is the time at which your script is running in Flash Player.

ActionScript terms such as method and object are defined in Chapter 2, “ActionScript Basics,”

on page 25.

Additional resources

Specific documentation about Flash and related products is available separately.

• For information about working in the Flash authoring environment, see Using Flash Help. For

information about working with components, see Using Components Help.

• For information about creating communication applications with Flash Communication

Server, see Developing Communications Applications and Managing Flash Communication Server.

• For information about accessing web services with Flash applications, see Using Flash Remoting.

The Macromedia DevNet website (www.macromedia.com/devnet) is updated regularly with the latest information on Flash, plus advice from expert users, advanced topics, examples, tips, and other updates. Check the website often for the latest news on Flash and how to get the most out of the program.

The Macromedia Flash Support Center (www.macromedia.com/support/flash) provides TechNotes, documentation updates, and links to additional resources in the Flash community.

10 Introduction: Getting Started with ActionScript

PART I

Welcome to ActionScript

This part includes basic information on the ActionScript language.

Chapter 1 includes information on what is new or changed in ActionScript and Flash Player 7. If you have used ActionScript before, be sure to review this information carefully.

If you are new to ActionScript, read Chapters 2 and 3 to get a good foundation for understanding ActionScript terminology and syntax and for learning how to write and debug your scripts.

Chapter 1: What’s New in Flash MX 2004 ActionScript . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Chapter 2: ActionScript Basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Chapter 3: Writing and Debugging Scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

PART I

CHAPTER 1

What’s New in Flash MX 2004 ActionScript

Macromedia Flash MX 2004 and Macromedia Flash MX Professional 2004 provide several enhancements that make it easier for you to write more robust scripts using the ActionScript language. These new features, which are discussed in this chapter, include new language elements, improved editing and debugging tools (see “ActionScript editor changes” on page 21 and

“Debugging changes” on page 22), and the introduction of a more object-oriented programming

model (see “New object-oriented programming model” on page 22).

This chapter also contains an extensive section that you should read carefully if you plan to publish any of your existing Flash MX or earlier files to Flash Player 7 (see “Porting existing

scripts to Flash Player 7” on page 15).

New and changed language elements

This section describes the ActionScript language elements that are new or changed in Flash MX

2004. To use any of these elements in your scripts, you must target Flash Player 7 (the default) when you publish your documents.

• The Array.sort() and Array.sortOn() methods let you add parameters to specify

additional sorting options, such as ascending and descending sorting, whether to consider case sensitivity when sorting, and so on.

• The Button.menu, MovieClip.menu, and TextField.menu properties work with the new

ContextMenu and ContextMenuItem classes to let you associate context menu items with Button, MovieClip, or TextField objects.

• The ContextMenu class and ContextMenuItem class let you customize the context menu that

is displayed when a user right-clicks (Microsoft Windows) or Control-clicks (Macintosh) in Flash Player.

• The Error class and the throw and try..catch..finally commands let you implement

more robust exception handling.

• The LoadVars.addRequestHeader() and XML.addRequestHeader() methods add or change

HTTP request headers (such as

• The MMExecute() function lets you issue Flash JavaScript API commands from ActionScript.

• (Windows only) The Mouse.onMouseWheel event listener is generated when the user scrolls

using the mouse wheel.

Content-Type or SOAPAction) sent with POST actions.

• The MovieClip.getNextHighestDepth() method lets you create MovieClip instances at

runtime and be guaranteed that their objects render in front of the other objects in a parent movie clip’s z-order space. The dynamically created MovieClip instances using the depth as a search index.

MovieClip.getInstanceAtDepth() method lets you access

• The MovieClip.getSWFVersion() method lets you determine which version of Flash Player

is supported by a loaded SWF file.

• The MovieClip.getTextSnapshot() method and the TextSnapshot object let you work with

text that is in static text fields in a movie clip.

• The MovieClip._lockroot property lets you specify that a movie clip will act as _root for

any movie clips loaded into it, or that the meaning of that movie clip is loaded into another movie clip.

_root in a movie clip won’t change if

• The MovieClipLoader class lets you monitor the progress of files as they are being loaded into

movie clips.

• The NetConnection class and NetStream class let you stream local video files (FLV files).

• The PrintJob class gives you (and the user) more control over printing from Flash Player.

• The Sound.onID3 event handler provides access to ID3 data associated with a Sound object

that contains an MP3 file.

• The Sound.ID3 property provides access to the metadata that is part of an MP3 file.

• The System class has new objects and methods, and the System.capabilities object has several

new properties.

• The TextField.condenseWhite property lets you remove extra white space from HTML text

fields that are rendered in a browser.

• The TextField.mouseWheelEnabled property lets you specify whether a text field’s contents

should scroll when the mouse pointer is positioned over a text field and the user rolls the mouse wheel.

• The TextField.StyleSheet class lets you create a style sheet object that contains text formatting

rules such as font size, color, and other formatting styles.

• The TextField.styleSheet property lets you attach a style sheet object to a text field.

• The TextFormat.getTextExtent() method accepts a new parameter, and the object it

returns contains a new member.

• The XML.addRequestHeader() method lets you add or change HTTP request headers (such

Content-Type or SOAPAction) sent with POST actions.

New security model and legacy SWF files

Rules for how Flash Player determines whether two domains are the same have changed in Flash Player 7. In addition, rules that determine whether and how a SWF file served from an HTTP domain can access a SWF file or load data from an HTTPS domain have changed. In most cases, these changes won’t affect you unless you are porting your existing SWF files to Flash Player 7.

However, if you have SWF files published for Flash Player 6 or earlier that load data from a file stored on a server, and the calling SWF is playing in Flash Player 7, the user might see a dialog box that didn’t appear before, asking whether to allow access. You can prevent this dialog box from appearing by implementing a policy file on the site where the data is stored. For more information on this dialog box, see “About compatibility with previous Flash Player security

models” on page 191.

14 Chapter 1: What’s New in Flash MX 2004 ActionScript

You might also need to implement a policy file if you are using runtime shared libraries. If either the loading or loaded SWF file is published for Flash Player 7 and the loading and loaded files aren’t served from the exact same domain, use a policy file to permit access. For more information on policy files, see “About allowing cross-domain data loading” on page 190.

Porting existing scripts to Flash Player 7

As with any new release, Flash Player 7 supports more ActionScript commands than previous versions of the player; you can use these commands to implement more robust scripts. (See “New

and changed language elements” on page 13.)However, if you used any of these commands in

your existing scripts, the script might not work correctly if you publish it for Flash Player 7.

For example, if you have a script with a function named Error, the script might appear to compile correctly but might not run as expected in Flash Player 7, because Error is now a built-in class (and thus a reserved word) in ActionScript. You can fix your script by renaming the Error function to something else, such as ErrorCondition.

Also, Flash Player 7 implements a number of changes that affect how one SWF file can access another SWF file, how external data can be loaded, and how local settings and data (such as privacy settings and locally persistent shared objects) can be accessed. Finally, the behavior of some existing features has changed.

If you have existing scripts written for Flash Player 6 or earlier that you want to publish for Flash Player 7, you might need to modify the scripts so they conform with the implementation of Flash Player 7 and work as designed. These modifications are discussed in this section.

ECMA-262 Edition 4 compliance

Several changes have been implemented in Flash Player 7 to conform more closely to the ECMA-262 Edition 4 proposal (see www.mozilla.org/js/language/es4/index.html). In addition to the class-based programming techniques available in ActionScript 2.0 (see “New object-oriented

programming model” on page 22), other features have been added and certain behaviors have

changed. Also, when publishing for Flash Player 7 and using ActionScript 2.0, you can cast one object type to another. For more information, see “Casting objects” on page 39. These capabilities don’t require you to update existing scripts; however, you may want to use them if you publish your scripts to Flash Player 7 and then continue to revise and enhance them.

Porting existing scripts to Flash Player 7 15

Unlike the changes mentioned above, the changes listed in the following table (some of which also improve ECMA compliance) may cause existing scripts to work differently than they did previously. If you used these features in existing scripts that you want to publish to Flash Player 7, review the changes to make sure your code still works as intended or to determine whether you need to rewrite your code. In particular, because

undefined is evaluated differently in certain

cases, you should initialize all variables in scripts that you port to Flash Player 7.

SWF file published for Flash Player 7 SWF file published for earlier versions of

Flash Player

Case sensitivity is supported (variable names that differ only in capitalization are interpreted as being different variables). This change also affects files loaded with with

#include and external variables loaded

LoadVars.load(). For more information, see

Case sensitivity is not supported (variable names that differ only in capitalization are interpreted as being the same variable).

“Case sensitivity” on page 29.

Evaluating

NaN. myCount +=1;

trace(myCount); // NaN

When undefined is converted to a string, the result is

undefined. firstname = "Joan ";

lastname = "Flender"; trace(firstname + middlename + lastname); // Joan undefinedFlender

When you convert a string to a Boolean value, the result is zero; the result is

undefined in a numeric context returns

true if the string has a length greater than

false for an empty string.

Evaluating undefined in a numeric context returns 0.

myCount +=1; trace(myCount); // 1

When undefined is converted to a string, the result is "" (an empty string).

firstname = "Joan "; lastname = "Flender"; trace(firstname + middlename + lastname); // Joan Flender

When you convert a string to a Boolean value, the string is first converted to a number; the result is

true if the number is nonzero, false

otherwise.

When setting the length of an array, only a valid number string sets the length. For example, "6" works but " 6" or "6xyz" does not.

my_array=new Array(); my_array[" 6"] ="x"; trace(my_array.length); // 0 my_array["6xyz"] ="x"; trace(my_array.length); // 0 my_array["6"] ="x"; trace(my_array.length); // 7

When setting the length of an array, even a malformed number string sets the length:

my_array=new Array(); my_array[" 6"] ="x"; trace(my_array.length); // 7 my_array["6xyz"] ="x"; trace(my_array.length); // 7 my_array["6"] ="x"; trace(my_array.length); // 7

16 Chapter 1: What’s New in Flash MX 2004 ActionScript

Domain-name rules for settings and local data

In Flash Player 6, superdomain matching rules are used by default when accessing local settings (such as camera or microphone access permissions) or locally persistent data (shared objects). That is, the settings and data for SWF files hosted at here.xyz.com, there.xyz.com, and xyz.com are shared, and are all stored at xyz.com.

In Flash Player 7, exact-domain matching rules are used by default. That is, the settings and data for a file hosted at here.xyz.com are stored at here.xyz.com, the settings and data for a file hosted at there.xyz.com are stored at there.xyz.com, and so on.

A new property,

System.exactSettings, lets you specify which rules to use. This property is

supported for files published for Flash Player 6 or later. For files published for Flash Player 6, the default value is Flash Player 7, the default value is

false, which means superdomain matching rules are used. For files published for

true, which means exact-domain matching rules are used.

If you use settings or persistent local data and want to publish a Flash Player 6 SWF file for Flash Player 7, you might need to set this value to

For more information, see

System.exactSettings on page 662.

false in the ported file.

Cross-domain and subdomain access between SWF files

When you develop a series of SWF files that communicate with each other—for example, when using

loadMovie(), MovieClip.loadMovie(), MovieClipLoader.LoadClip(), or Local

Connection objects—you might host the movies in different domains, or in different subdomains of a single superdomain.

In files published for Flash Player 5 or earlier, there were no restrictions on cross-domain or subdomain access.

In files published for Flash Player 6, you could use the or

System.security.allowDomain() method to specify permitted cross-domain access (for

LocalConnection.allowDomain handler

example, to let a file at someSite.com be accessed by a file at someOtherSite.com), and no command was needed to permit subdomain access (for example, a file at www.someSite.com could be accessed by a file at store.someSite.com).

Files published for Flash Player 7 implement access between SWF files differently from earlier versions in two ways. First, Flash Player 7 implements exact-domain matching rules instead of superdomain matching rules. Therefore, the file being accessed (even if it is published for a Player version earlier than Flash Player 7) must explicitly permit cross-domain or subdomain access; this topic is discussed below. Second, a file hosted at a site using a secure protocol (HTTPS) must explicitly permit access from a file hosted at a site using an insecure protocol (HTTP or FTP); this topic is discussed in the next section (see “HTTP to HTTPS protocol access between SWF

files” on page 19).

Porting existing scripts to Flash Player 7 17

Because Flash Player 7 implements exact-domain matching rules instead of superdomain matching rules, you might have to modify existing scripts if you want to access them from files that are published for Flash Player 7. (You can still publish the modified files for Flash Player 6.) If you used any

LocalConnection.allowDomain() or System.security.allowDomain()

statements in your files and specified superdomain sites to permit, you must change your parameters to specify exact domains instead. The following code shows an example of the kinds of changes you might have to make:

// Flash Player 6 commands in a SWF file at www.anyOldSite.com // to allow access by SWF files that are hosted at www.someSite.com // or at store.someSite.com System.security.allowDomain("someSite.com"); my_lc.allowDomain = function(sendingDomain) {

return(sendingDomain=="someSite.com"); } // Corresponding commands to allow access by SWF files // that are published for Flash Player 7 System.security.allowDomain("www.someSite.com", "store.someSite.com"); my_lc.allowDomain = function(sendingDomain) {

return(sendingDomain=="www.someSite.com" ||

sendingDomain=="store.someSite.com");

}

You might also have to add statements like these to your files if you aren’t currently using them. For example, if your SWF file is hosted at www.someSite.com and you want to allow access by a SWF file published for Flash Player 7 at store.someSite.com, you must add statements like the following to the file at www.someSite.com (you can still publish the file at www.someSite.com for Flash Player 6):

System.security.allowDomain("store.someSite.com"); my_lc.allowDomain = function(sendingDomain) {

return(sendingDomain=="store.someSite.com"); }

To summarize, you might have to modify your files to add or change allowDomain statements if you publish files for Flash Player 7 that meet the following conditions:

• You implemented cross-SWF scripting (using loadMovie(), MovieClip.loadMovie(),

MovieClipLoader.LoadClip(), or Local Connection objects).

• The called SWF file (of any version) is not hosted at a site using a secure protocol (HTTPS), or

the calling and called SWF files are both hosted at HTTPS sites. (If only the called SWF file is

HTTPS, see “HTTP to HTTPS protocol access between SWF files” on page 19.)

• The SWF files are not in same domain (for example, one file is at www.domain.com and one is

at store.domain.com).

18 Chapter 1: What’s New in Flash MX 2004 ActionScript

You have to make the following changes:

• If the called SWF file is published for Flash Player 7, include System.security.allowDomain

LocalConnection.allowDomain in the called SWF file, using exact domain-

name matching.

• If the called SWF file is published for Flash Player 6, modify the called file to add or change a

System.security.allowDomain or LocalConnection.allowDomain statement, using exact

domain-name matching, as shown in the code examples earlier in this section. You can publish

the modified file for either Flash Player 6 or 7.

• If the called SWF file is published for Flash Player 5 or earlier, port the called file to

Flash Player 6 or 7 and add a

domain-name matching, as shown in the code examples earlier in this section.

(LocalConnection objects aren’t supported in Flash Player 5 or earlier.)

HTTP to HTTPS protocol access between SWF files

As discussed in the previous section, rules for cross-domain and subdomain access have changed in Flash Player 7. In addition to the exact-domain matching rules now being implemented, you must explicitly permit files hosted at sites using a secure protocol (HTTPS) to be accessed by files hosted at sites using an insecure protocol. Depending on whether the called file is published for Flash Player 7 or Flash Player 6, you must implement either one of the (see “Cross-domain and subdomain access between SWF files” on page 17), or use the new

LocalConnection.allowInsecure Domain or System.security.allowInsecureDomain()

statements.

Warning: Implementing an allowInsecureDomain() statement compromises the security offered by the HTTPS protocol. You should make these changes only if you can’t reorganize your site so that all SWF files are served from the HTTPS protocol.

System.security.allowDomain statement, using exact

allowDomain statements

The following code shows an example of the kinds of changes you might have to make:

// Commands in a Flash Player 6 SWF file at https://www.someSite.com // to allow access by Flash Player 7 SWF files that are hosted // at http://www.someSite.com or at http://www.someOtherSite.com System.security.allowDomain("someOtherSite.com"); my_lc.allowDomain = function(sendingDomain) {

return(sendingDomain=="someOtherSite.com"); } // Corresponding commands in a Flash Player 7 SWF file // to allow access by Flash Player 7 SWF files that are hosted // at http://www.someSite.com or at http://www.someOtherSite.com System.security.allowInsecureDomain("www.someSite.com",

"www.someOtherSite.com"); my_lc.allowInsecureDomain = function(sendingDomain) {

return(sendingDomain=="www.someSite.com" ||

sendingDomain=="www.someOtherSite.com");

}

You might also have to add statements like these to your files if you aren’t currently using them. A modification might be necessary even if both files are in same domain (for example, a file in http://www.domain.com is calling a file in https://www.domain.com).

Porting existing scripts to Flash Player 7 19

To summarize, you might have to modify your files to add or change statements if you publish files for Flash Player 7 that meet the following conditions:

• You implemented cross-SWF scripting (using loadMovie(), MovieClip.loadMovie(),

MovieClipLoader.LoadClip(), or Local Connection objects).

• The calling file is not hosted using an HTTPS protocol, and the called file is HTTPS.

You must make the following changes:

• If the called file is published for Flash Player 7, include

System.security.allowInsecureDomain or LocalConnection.allowInsecureDomain in

the called file, using exact domain-name matching, as shown in the code examples earlier in

this section. This statement is required even if the calling and called SWF files are in

same domain.

• If the called file is published for Flash Player 6 or earlier, and both the calling and called files

are in same domain (for example, a file in http://www.domain.com is calling a file in https://

www.domain.com), no modification is needed.

• If the called file is published for Flash Player 6, the files are not in same domain, and you don’t

want to port the called file to Flash Player 7, modify the called file to add or change a

System.security.allowDomain or LocalConnection.allowDomain statement, using exact

domain-name matching, as shown in the code examples earlier in this section.

• If the called file is published for Flash Player 6 and you want to port the called file to Flash

Player 7, include

LocalConnection.allowInsecureDomain in the called file, using exact domain-name

matching, as shown in the code examples earlier in this section. This statement is required even

if both files are in same domain.

System.security.allowInsecureDomain or

• If the called file is published for Flash Player 5 or earlier, and both files are not in the same

domain, you can do one of two things. You can either port the called file to Flash Player 6 and

add or change a

matching, as shown in the code examples earlier in this section, or you can port the called file

to Flash Player 7, and include a

called file, using exact domain-name matching, as shown in the code examples earlier in

this section.

System.security.allowDomain statement, using exact domain-name

System.security.allowInsecureDomain statement in the

Server-side policy files for permitting access to data

A Flash document can load data from an external source by using one of the following data loading calls:

LoadVars.sendAndLoad(), loadVariables(), loadVariablesNum(), MovieClip.loadVariables()

XML.load(), XML.sendAndLoad(), LoadVars.load(),

, XMLSocket.connect(), and Macromedia Flash Remoting (NetServices.createGatewayConnection). Also, a SWF file can import runtime shared libraries (RSLs), or assets defined in another SWF file, at runtime. By default, the data or RSL must reside in the same domain as the SWF file that is loading that external data or media.

To make data and assets in runtime shared libraries available to SWF files in different domains, you should use a cross-domain policy file. A cross-domain policy file is an XML file that provides a way for the server to indicate that its data and documents are available to SWF files served from certain domains, or from all domains. Any SWF file that is served from a domain specified by the server’s policy file is permitted to access data or RSLs from that server.

20 Chapter 1: What’s New in Flash MX 2004 ActionScript

If you are loading external data, you should create policy files even if you don’t plan to port any of your files to Flash Player 7. If you are using RSLs, you should create policy files if either the calling or called file is published for Flash Player 7.

For more information, see “About allowing cross-domain data loading” on page 190.

ActionScript editor changes

The ActionScript editor has been updated in a number of ways to make it more robust and easier to use. These changes are summarized in this section.

Word wrapping You can now use the Options pop-up menu in the Script pane, Debugger

panel, and Output panel to enable or disable word wrapping. You can also toggle word wrapping using the pop-up menu in the Actions panel. The keyboard shortcut is Control+Shift+W (Windows) or Command+Shift+W (Macintosh).

Viewing context-sensitive help When your pointer is positioned over an ActionScript

language element in the Actions toolbox or in the Script pane, you can use the View Help item in the context menu to display a help page about that element.

Importing scripts When you select Import Script from the pop-up menu in the Actions panel,

the imported script is copied into the script at the insertion point in your code file. In previous versions of Flash, importing a script overwrote the contents of the existing script.

Single-click breakpoints To add a debugging breakpoint before a line of code in the Debugger

panel or the Script pane of the Actions panel, you can click in the left margin. In previous versions of Flash, clicking in the left margin selected a line of code. The new way to select a line of code is to Control-click (Windows) or Command-click (Macintosh).

Normal and expert modes no longer in Actions panel In previous versions of Flash, you could

work in the Actions panel either in normal mode, in which you filled in options and parameters to create code, or in expert mode, in which you added commands directly into the Script pane. In Flash MX 2004 and Flash MX Professional 2004, you can work in the Actions panel only by adding commands directly to the Script pane. You can still drag commands from the Actions toolbox into the Script pane or use the Add (+) button above the Script pane to add commands to a script.

Pinning multiple scripts You can pin multiple scripts within a FLA file along the bottom of the

Script pane in the Actions panel. In previous versions of Flash, you could pin only one script at atime.

Script navigator The left side of the Actions panel now contains two panes: the Actions toolbox

and a new Script navigator. The Script navigator is a visual representation of the structure of your FLA file; you can navigate through your FLA file here to locate ActionScript code.

Integrated Script window for editing external files (Flash Professional only) You can use the

ActionScript editor in a Script window (separate from the Actions panel) to write and edit external script files. Syntax coloring, code hinting, and other preferences are supported in the Script window, and the Actions toolbox is also available. To display the Script window, use File > New and then select the type of external file you want to edit. You can have multiple external files open at the same time; filenames are displayed on tabs across the top of the Script window. (The tabs appear only in Windows.)

ActionScript editor changes 21

Debugging changes

This section describes changes that improve your ability to debug your scripts.

Output window changed to Output panel You can now move and dock the Output panel in

the same way as any other panel in Flash.

Improved error reporting at compile time In addition to providing more robust exception

handling, ActionScript 2.0 provides a number of new compile-time errors. For more information, see Appendix A, “Error Messages,” on page 783.

Improved exception handling The Error class and the throw and try..catch..finally

commands let you implement more robust exception handling.

New object-oriented programming model

The ActionScript language has grown and developed since its introduction several years ago. With each new release of Flash, additional keywords, objects, methods, and other language elements have been added to the language. However, unlike earlier releases of Flash, Flash MX 2004 and Flash MX Professional 2004 introduce several new language elements that implement objectoriented programming in a more standard way than before. Because these language elements represent a significant enhancement to the core ActionScript language, they represent a new version of ActionScript itself: ActionScript 2.0.

ActionScript 2.0 is not a new language. Rather, it comprises a core set of language elements that make it easier to develop object-oriented programs. With the introduction of keywords such as

class, interface, extends, and implements, ActionScript syntax is now easier to learn for

programmers familiar with other languages. New programmers can learn more standard terminology that they can apply to other object-oriented languages they may study in the future.

ActionScript 2.0 supports all the standard elements of the ActionScript language; it simply enables you to write scripts that more closely adhere to standards used in other object-oriented languages, such as Java. ActionScript 2.0 should be of interest primarily to intermediate or advanced Flash developers who are building applications that require the implementation of classes and subclasses. ActionScript 2.0 also lets you declare the object type of a variable when you create it (see “Strict data typing” on page 38) and provides significantly improved compiler errors (see Appendix A, “Error Messages,” on page 783).

The language elements that are new in ActionScript 2.0 are listed below.

• class

• extends

• implements

• interface

• dynamic

• static

• public

• private

• get

• set

• import

22 Chapter 1: What’s New in Flash MX 2004 ActionScript

Key facts about ActionScript 2.0 include the following points:

• Scripts that use ActionScript 2.0 to define classes or interfaces must be stored as external script

files, with a single class defined in each script; that is, classes and interfaces cannot be defined in the Actions panel.

• You can import individual class files implicitly (by storing them in a location specified by

global or document-specific search paths and then using them in a script) or explicitly (by using the

import command); you can import packages (collections of class files in a directory)

by using wildcards.

• Applications developed with ActionScript 2.0 are supported by Flash Player 6 and later.

Caution: The default publish setting for new files created in Flash MX 2004 is ActionScript 2.0. If you plan to modify an existing FLA file to use ActionScript 2 specifies ActionScript 2 although Flash will not generate compiler errors.

.0 in its publish settings. If it does not, your file will compile incorrectly,

For more information on using ActionScript 2.0 to write object-oriented programs in Flash, see

Chapter 9, “Creating Classes with ActionScript 2.0,” on page 155.

.0 syntax, ensure that the FLA file

New object-oriented programming model 23

24 Chapter 1: What’s New in Flash MX 2004 ActionScript

CHAPTER 2

ActionScript Basics

ActionScript has rules of grammar and punctuation that determine which characters and words are used to create meaning and in which order they can be written. For example, in English, a period ends a sentence. In ActionScript, a semicolon ends a statement.

The following general rules apply to all ActionScript. Most ActionScript terms also have individual requirements; for the rules for a specific term, see its entry in Chapter 12,

“ActionScript Dictionary,” on page 205.

Differences between ActionScript and JavaScript

ActionScript is similar to the core JavaScript programming language. You don’t need to know JavaScript to use and learn ActionScript; however, if you know JavaScript, ActionScript will appear familiar.

This manual does not attempt to teach general programming. There are many resources that provide more information about general programming concepts and the JavaScript language.

• The European Computers Manufacturers Association (ECMA) document ECMA-262 is

derived from JavaScript and serves as the international standard for the JavaScript language. ActionScript is based on the ECMA-262 specification.

• Netscape DevEdge Online has a JavaScript Developer Central site (http://

developer.netscape.com/tech/javascript/index.html) that contains documentation and articles

useful for understanding ActionScript. The most valuable resource is the Core JavaScript Guide.

Some of the differences between ActionScript and JavaScript are as follows:.

• ActionScript does not support browser-specific objects such as Document, Window,

and Anchor.

• ActionScript does not completely support all the JavaScript built-in objects.

• ActionScript does not support some JavaScript syntax constructs, such as statement labels.

• In ActionScript, the eval() action can perform only variable references.

Unicode support for ActionScript

Macromedia Flash MX 2004 and Macromedia Flash MX Professional 2004 support Unicode text encoding for ActionScript. This means that you can include text in different languages in an ActionScript file. For example, you could include text in English, Japanese, and French in the same file.

You can set ActionScript preferences to specify the type of encoding to use when importing or exporting ActionScript files. You can select either UTF-8 encoding or Default Encoding. UTF-8 is 8-bit Unicode format; Default Encoding is the encoding form supported by the language your system is currently using, also called the traditional code page.

In general, if you are importing or exporting ActionScript files in UTF-8 format, use the UTF-8 preference. If you are importing or exporting files in the traditional code page in use on your system, use the Default Encoding preference.

If text in your scripts doesn’t look as expected when you open or import a file, change the import encoding preference. If you receive a warning message when exporting ActionScript files, you can change the export encoding preference or turn this warning off in ActionScript preferences.

To select text encoding options for importing or exporting ActionScript files:

1 In the Preferences dialog box (Edit > Preferences), click the ActionScript tab. 2 Under Editing Options, do one or both of the following:

■ For Open/Import, select UTF-8 to open or import using Unicode encoding, or select

Default Encoding to open or import using the encoding form of the language currently used by your system.

■ For Save/Export, select UTF-8 to save or export using Unicode encoding, or select Default

Encoding to save or export using the encoding form of the language currently used by your system.

To turn the export encoding warning off or on:

1 In the Preferences dialog box (Edit > Preferences), click the Warnings tab. 2 Select or deselect Warn on Encoding Conflicts When Exporting .as Files.

Caution: The Test Movie command (see “Debugging your scripts” on page 68) will fail if any part of the SWF file path has characters that cannot be represented using the MBCS encoding scheme. For example, Japanese paths on an English system will not work. All areas of the application that use the external player are subject to this limitation.

Terminology

As with any scripting language, ActionScript uses its own terminology. The following list provides an introduction to important ActionScript terms.

Actions are statements that instruct a SWF file to do something while it is playing. For example,

gotoAndStop() sends the playhead to a specific frame or label. In this manual, the terms action

and statement are interchangeable.

Boolean is a true or false value.

Classes are data types that you can create to define a new type of object. To define a class,

you use the Actions panel).

26 Chapter 2: ActionScript Basics

class keyword in an external script file (not in a script you are writing in the

Constants are elements that don’t change. For example, the constant Key.TAB always has the

same meaning: it indicates the Tab key on a keyboard. Constants are useful for comparing values.

Constructors are functions that you use to define the properties and methods of a class.

By definition, constructors are functions within a class definition that have the same name as the class. For example, the following code defines a Circle class and implements a constructor function:

// file Circle.as class Circle {

private var radius:Number private var circumference:Number

// constructor

function Circle(radius:Number) {

circumference = 2 * Math.PI * radius;

}

The term constructor is also used when you create (instantiate) an object based on a particular class. The following statements are constructors for the built-in Array class and the custom Circle class:

my_array:Array = new Array(); my_circle:Circle = new Circle();

Data types

describe the kind of information a variable or ActionScript element can hold. The ActionScript data types are String, Number, Boolean, Object, MovieClip, Function, null, and undefined. For more information, see “About data types” on page 34.

Events are actions that occur while a SWF file is playing. For example, different events are

generated when a movie clip loads, the playhead enters a frame, the user clicks a button or movie clip, or the user types on the keyboard.

Event handlers are special actions that manage events such as mouseDown or load. There are two

kinds of ActionScript event handlers: event handler methods and event listeners. (There are also two event handlers,

on() and onClipEvent(), that you can assign directly to buttons and movie

clips.) In the Actions toolbox, each ActionScript object that has event handler methods or event listeners has a subcategory called Events or Listeners. Some commands can be used both as event handlers and as event listeners and are included in both subcategories.

Expressions are any legal combination of ActionScript symbols that represent a value. An

expression consists of operators and operands. For example, in the expression x + 2, x and 2 are operands and

Functions are blocks of reusable code that can be passed parameters and can return a value. For

+ is an operator.

more information, see “Creating functions” on page 51.

Identifiers are names used to indicate a variable, property, object, function, or method. The first

character must be a letter, underscore (

_), or dollar sign ($). Each subsequent character must be a

letter, number, underscore, or dollar sign. For example, firstName is the name of a variable.

Instances are objects that belong to a certain class. Each instance of a class contains all the

properties and methods of that class. For example, all movie clips are instances of the MovieClip class, so you can use any of the methods or properties of the MovieClip class with any movie clip instance.

Terminology 27

Instance names are unique names that let you target movie clip and button instances in scripts.

You use the Property inspector to assign instance names to instances on the Stage. For example, a master symbol in the library could be called the SWF file could have the instance names following code sets a variable called

score inside each movie clip instance by using

counter and the two instances of that symbol in

scorePlayer1_mc and scorePlayer2_mc. The

instance names:

_root.scorePlayer1_mc.score += 1; _root.scorePlayer2_mc.score -= 1;

You can use special suffixes when naming instances so that code hints (see “Using code hints”

on page 63) appear as you type your code. For more information, see “Using suffixes to trigger code hints” on page 62.

Keywords are reserved words that have special meaning. For example, var is a keyword used to

declare local variables. You cannot use a keyword as an identifier. For example,

var is not a legal

variable name. For a list of keywords, see “Keywords” on page 33.

Methods are functions associated with a class. For example, getBytesLoaded() is a built-in

method associated with the MovieClip class. You can also create functions that act as methods, either for objects based on built-in classes or for objects based on classes that you create. For example, in the following code,

clear() becomes a method of a controller object that you

have previously defined:

function reset(){

this.x_pos = 0;

this.x_pos = 0; } controller.clear = reset; controller.clear();

Objects

are collections of properties and methods; each object has its own name and is an instance of a particular class. Built-in objects are predefined in the ActionScript language. For example, the built-in Date object provides information from the system clock.

Operators are terms that calculate a new value from one or more values. For example, the

addition (

+) operator adds two or more values together to produce a new value. The values that

operators manipulate are called operands.

Parameters (also called arguments) are placeholders that let you pass values to functions.

For example, the following

firstName and hobby:

function welcome(firstName, hobby) {

welcomeText = "Hello, " + firstName + "I see you enjoy " + hobby;

}

Packages

are directories that contain one or more class files, and reside in a designated classpath

welcome() function uses two values it receives in the parameters

directory (see “Understanding the classpath” on page 169).

Properties are attributes that define an object. For example, _visible is a property of all movie

clips that defines whether a movie clip is visible or hidden.

28 Chapter 2: ActionScript Basics

Target paths are hierarchical addresses of movie clip instance names, variables, and objects in a

SWF file. You name a movie clip instance in the movie clip Property inspector. (The main Timeline always has the name

_root.) You can use a target path to direct an action at a movie clip

or to get or set the value of a variable. For example, the following statement is the target path to the variable

_root.stereoControl.volume

volume inside the movie clip stereoControl:

For more information on target paths, see “Absolute and relative target paths” in Using Flash Help.

Variables are identifiers that hold values of any data type. Variables can be created, changed, and

updated. The values they store can be retrieved for use in scripts. In the following example, the identifiers on the left side of the equal signs are variables:

var x = 5; var name = "Lolo"; var c_color = new Color(mcinstanceName);

For more information on variables, see “About variables” on page 40.

Syntax

As with any language, ActionScript has syntax rules that you must follow in order to create scripts that can compile and run correctly. This section describes the elements that comprise ActionScript syntax.

Case sensitivity

In a case-sensitive programming language, variable names that differ only in case ( are considered different from each other. Therefore, it’s good practice to follow consistent capitalization conventions, such as those used in this manual, to make it easy to identify names of functions and variables in ActionScript code.

When you publish files for Flash Player 7 or later, Flash implements case sensitivity whether you are using ActionScript 1 or ActionScript 2.0. This means that keywords, class names, variables, method names, and so on are all case sensitive. For example:

// In file targeting Flash Player 7 // and either ActionScript 1 or ActionScript 2.0 // // Sets properties of two different objects cat.hilite = true; CAT.hilite = true;

book and Book)

// Creates three different variables var myVar=10; var myvar=10; var mYvAr=10; // Does not generate an error var array = new Array(); var date = new Date();

This change also affects external variables loaded with LoadVars.load().

Syntax 29

In addition, case sensitivity is implemented for external scripts, such as ActionScript 2.0 class files or scripts that you import using the

#include command. If you are publishing files for Flash

Player 7 and have previously created external files that you add to your scripts by using the

#include statement, you should review each file and confirm that you used consistent

capitalization throughout. One way to do this is to open the file in the Script window (Flash Professional only) or, in a new FLA file, set your publish settings to Flash Player 7 and copy the file’s contents into the Actions panel. Then use the Check Syntax button (see “Checking syntax

and punctuation” on page 66) or publish your file; errors that are caused by naming conflicts

appear in the Output panel.

When Syntax coloring is enabled, language elements written with correct capitalization are blue by default. For more information, see “Keywords” on page 33 and “Syntax highlighting”

on page 61.

Dot syntax

In ActionScript, a dot (

.) is used to indicate the properties or methods related to an object or

movie clip. It is also used to identify the target path to a movie clip, variable, function, or object. A dot syntax expression begins with the name of the object or movie clip followed by a dot, and ends with the element you want to specify.

For example, the expression

As another example, movie clip variable of the instance

_x movie clip property indicates a movie clip’s x axis position on the Stage. The

ballMC._x refers to the _x property of the movie clip instance ballMC.

submit is a variable set in the form movie clip, which is nested inside the

shoppingCart. The expression shoppingCart.form.submit = true sets the submit

form to true.

Expressing a method of an object or movie clip follows the same pattern. For example, the

play() method of the ball_mc movie clip instance moves the playhead in the Timeline of ball_mc, as shown in the following statement:

ball_mc.play();

Dot syntax also uses two special aliases, _root and _parent. The alias _root refers to the main Timeline. You can use the following statement calls the function

_root alias to create an absolute target path. For example, the

buildGameBoard() in the movie clip functions on the

main Timeline:

_root.functions.buildGameBoard();

You can use the alias _parent to refer to a movie clip in which the current object is nested. You can also use _parent to create a relative target path. For example, if the movie clip dog_mc is nested inside the movie clip

animal_mc to stop:

_parent.stop();

animal_mc, the following statement on the instance dog_mc tells

Slash syntax

Slash syntax was used in Flash 3 and 4 to indicate the target path of a movie clip or variable. This syntax is still supported by Flash Player 7, but its use is not recommended, and slash syntax is not supported in ActionScript 2.0. However, if you are creating content intended specifically for Flash Player 4, you must use slash syntax. For more information, see “Using slash syntax”

on page 797.

30 Chapter 2: ActionScript Basics

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