Category:Actionscript
From Flash Wiki
ActionScript is a scripting language based on ECMAScript. ActionScript is used primarily for the development of websites and software using the Adobe Flash Player platform (in the form of SWF files embedded into Web pages), but is also used in some database applications (such as Alpha Five), and in basic robotics, as with the Make Controller Kit. Originally developed by Macromedia, the language is now owned by Adobe (which acquired Macromedia in 2005). ActionScript was initially designed for controlling simple 2D vector animations made in Adobe Flash (formerly Macromedia Flash). Later versions added functionality allowing for the creation of Web-based games and rich Internet applications with streaming media (such as video and audio).
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[edit] History
ActionScript started as a scripting language for Macromedia's Shockwave Flash authoring tool, now developed by Adobe as Adobe Flash. The first three versions of the Flash authoring tool provided limited interactivity features. Early Flash developers could attach a simple command, called an "action", to a button or a frame. The set of actions was basic navigation controls, with commands such as "play", "stop", "getURL", and "gotoAndPlay".
With the release of Flash 4 in 1999, this simple set of actions became a small scripting language. New capabilities introduced for Flash 4 included variables, expressions, operators, if statements, and loops. Although referred to internally as "ActionScript", the Flash 4 user manual and marketing documents continued to use the term "actions" to describe this set of commands .
[edit] Timeline by player
- Flash Player 2: The first version with scripting support. Actions included gotoAndPlay, gotoAndStop, nextFrame and nextScene for timeline control.
- Flash Player 3: Expanded basic scripting support with the ability to load external SWFs (loadMovie).
- Flash Player 4: First player with a full scripting implementation (called Actions). The scripting was a flash based syntax and contained support for loops, conditionals, variables and other basic language constructs.
- Flash Player 5: Included the first version of ActionScript. Used prototype-based programming based on ECMAScript, and allowed full procedural programming and object-oriented programming.
- Flash Player 6: Added an event handling model, accessibility controls and support for switch. The first version with support for the AMF and RTMP protocols which allowed for ondemand audio/video streaming.
- Flash Player 7: Additions include CSS styling for text and support for ActionScript 2.0, a programming language based on the ECMAScript 4 Netscape Proposal with class-based inheritance. However, ActionScript 2.0 can cross compile to ActionScript 1.0 byte-code, so that it can run in Flash Player 6.
- Flash Player 8: Further extended ActionScript 1/ActionScript 2 by adding new class libraries with APIs for controlling bitmap data at run-time, file uploads and live filters for blur and dropshadow.
Example of ActionScript 2.0 running on Macromedia Flash 8.
- Flash Player 9 (initially called 8.5): Added ActionScript 3.0 with the advent of a new virtual machine, called AVM2 (ActionScript Virtual Machine 2), which coexists with the previous AVM1 needed to support legacy content. Performance increases were a major objective for this release of the player including a new JIT compiler. Support for binary sockets, E4X XML parsing, full-screen mode and Regular Expressions were added. This is the first release of the player to be titled Adobe Flash Player.
- Flash Player 10 (initially called Astro): Added basic 3D manipulation, such as rotating on the X, Y, and Z axis, and a 3D drawing API. Ability to create custom filters using Adobe Pixel Bender. Graphic processing is now offloaded to the GPU which gives a noticeable decrease to rendering time for each frame, basically higher Frame rate. There is a new sound API which allows for custom creation of audio in flash, something that has never been possible before. [2]
[edit] Timeline by ActionScript version
2000–2003: ActionScript "1.0" With the release of Flash 5 in September 2000, the "actions" from Flash 4 were enhanced once more and named "ActionScript" for the first time.[3] This was the first version of ActionScript with influences from JavaScript and the ECMA-262 (Third Edition) standard, supporting the said standard's object model and many of its core data types. Local variables may be declared with the var statement, and user-defined functions with parameter passing and return values can also be created. Notably, ActionScript could now also be typed with a text editor rather than being assembled by choosing actions from drop-down lists and dialog box controls. With the next release of its authoring tool, Flash MX, and its corresponding player, Flash Player 6, the language remained essentially unchanged; there were only minor changes, such as the addition of the switch statement and the "strict equality" (===) operator, which brought it closer to being ECMA-262-compliant. Two important features of ActionScript that distinguish it from later versions are its loose type system and its reliance on prototype-based inheritance. Loose typing refers to the ability of a variable to hold any type of data. This allows for rapid script development and is particularly well-suited for small-scale scripting projects. Prototype-based inheritance is the ActionScript 1.0 mechanism for code reuse and object-oriented programming. Instead of a class keyword that defines common characteristics of a class, ActionScript 1.0 uses a special object that serves as a "prototype" for a class of objects. All common characteristics of a class are defined in the class's prototype object and every instance of that class contains a link to that prototype object.
2003–2006: ActionScript 2.0 The next major revision of the language, ActionScript 2.0, was introduced in September 2003 with the release of Flash MX 2004 and its corresponding player, Flash Player 7. In response to user demand for a language better equipped for larger and more complex applications, ActionScript 2.0 featured compile-time type checking and class-based syntax, such as the keywords class and extends. (While this allowed for a more flexible object-oriented programming approach, the code would still be compiled to ActionScript 1.0 bytecode, allowing it to be used on the preceding Flash Player 6 as well. In other words, the class-based inheritance syntax was a layer on top of the existing prototype-based system.) With ActionScript 2.0, developers could constrain variables to a specific type by adding a type annotation so that type mismatch errors could be found at compile-time. ActionScript 2.0 also introduced class-based inheritance syntax so that developers could create classes and interfaces, much as they would in class-based languages such as Java and C++. This version conformed partially to the ECMAScript Fourth Edition draft specification.
2006–today: ActionScript 3.0 In June 2006, ActionScript 3.0 debuted with Adobe Flex 2.0 and its corresponding player, Flash Player 9. ActionScript 3.0 was a fundamental restructuring of the language, so much so that it uses an entirely different virtual machine. Flash Player 9 contains two virtual machines, AVM1 for code written in ActionScript 1.0 and 2.0, and AVM2 for content written in ActionScript 3.0. ActionScript 3.0 is faster than its previous versions but still not fast enough for fullscreen applications with many objects active. Actionscript 3.0 has limited support for hardware acceleration ( DirectX, OpenGL ).
The update to the language introduced several new features:
- Compile-time and runtime type checking—type information exists at both compile-time and runtime.
- Improved performance from a class-based inheritance system separate from the prototype-based inheritance system.
- Support for packages, namespaces, and regular expressions.
- Compiles to an entirely new type of bytecode, incompatible with ActionScript 1.0 and 2.0 bytecode.
- Revised Flash Player API, organized into packages.
- Unified event handling system based on the DOM event handling standard.
- Integration of ECMAScript for XML (E4X) for purposes of XML processing.
- Direct access to the Flash runtime display list for complete control of what gets displayed at runtime.
- Completely conforming implementation of the ECMAScript fourth edition draft specification.
[edit] Flash Lite
- Flash Lite 1.0: Flash Lite is the Flash technology specifically developed for mobile phones and consumer electronics devices. Supports Flash 4 ActionScript.
- Flash Lite 1.1: Flash 4 ActionScript support and additional device APIs added.
- Flash Lite 2.0 and 2.1: Added support for Flash 7 ActionScript 2.0 and some additional fscommand2 API.
- Flash Lite 3: Added support for Flash 8 ActionScript 2.0 and also FLV video playback.
[edit] Syntax
ActionScript code is free form and thus may be created with whichever amount or style of whitespace that the author desires. The basic syntax is derived from ECMAScript.
[edit] ActionScript 2.0
The following code, which works in any compliant player, creates a text field at depth 0, at position (0, 0) on the screen (measured in pixels), that is 100 pixels wide and high. Then the text parameter is set to the "Hello, world!" string, and it is automatically displayed in the player:
createTextField("greet", 0, 0, 0, 100, 100);
greet.text = "Hello, world";
When writing external ActionScript 2.0 class files the above example could be written in a file named Greeter.as as following.
class com.example.Greeter extends MovieClip
{
public function Greeter() {}
public function onLoad() :Void
{
var txtHello:TextField = this.createTextField("txtHello", 0, 0, 0, 100, 100.);
txtHello.text = "Hello, world";
}
}
[edit] ActionScript 3.0
ActionScript 3.0 has a similar syntax to ActionScript 2.0 but a different set of APIs for creating objects. Compare the below to the previous ActionScript 2.0 version:
var greet:TextField = new TextField(); greet.text = "Hello World"; this.addChild(greet);
Minimal ActionScript 3.0 programs may be somewhat larger and more complicated due to the increased separation of the programming language and the Flash IDE.
Presume the following file to be Greeter.as:
package com.example
{
import flash.text.TextField; import flash.display.Sprite;
public class Greeter extends Sprite { public function Greeter() { var txtHello:TextField = new TextField(); txtHello.text = "Hello World"; addChild(txtHello); } }
}
Finally, an example of using ActionScript when developing Flex applications, again presuming the following content to be in a file named Greeter.as:
package
{
public class Greeter { public static function sayHello():String { var greet:String = "Hello, world!"; return greet; } }
}
This code will work with the following MXML application file:
<?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" xmlns="*" layout="vertical" c reationComplete="initApp()">
<mx:Script> <![CDATA[ public function initApp():void { // Prints our "Hello, world!" message into "mainTxt". mainTxt.text = Greeter.sayHello(); } ]]> </mx:Script>
<mx:Label id="title" fontSize="24" fontStyle="bold" text='"Hello, world!" E xample'/> <mx:TextArea id="mainTxt" width="250"/>
</mx:Application>
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