About native extensions
What is Adobe AIR?
Adobe® AIR® is a cross-operating system runtime that allows
content developers to build rich Internet applications (RIAs). The
developers can deploy the RIAs to the desktop, mobile devices, and
digital home devices. AIR applications can be built using Adobe®
and Ajax (HTML-based). For more information about the Adobe Flash Platform
tools that you can use to build AIR applications, see
Adobe Flash Platform tools for AIR development
Building Adobe AIR Applications
What is Adobe ActionScript?
SWF-based AIR applications can use Adobe ActionScript® 3.0. ActionScript 3.0 is an object-oriented
language that can add interactivity and data-handling to RIAs. For
more information about the language, see
Learning ActionScript 3.0
ActionScript 3.0 Developer's Guide
ActionScript provides many built-in classes. For example, MovieClip,
Array, and NetConnection are built-in ActionScript classes. Additionally,
a content developer can create application-specific classes. Sometimes
an application-specific class derives from a built-in class.
The runtime executes the code in ActionScript classes. The runtime
What is a native extension?
A native extension is a combination of:
Native code. Native code is defined here as code that executes
outside the runtime. For example, code that you write in C is native
code. On some platforms, Java code is supported in extensions. For
the purpose of this documentation, this is also considered “native”
Reasons to write a native extension include the following:
A native code implementation provides access to device-specific
features. These device-specific features are not available in the
built-in ActionScript classes, and are not possible to implement
in application-specific ActionScript classes. The native code implementation
can provide such functionality because it has access to device-specific
hardware and software.
A native code implementation can sometimes be faster than
an implementation that uses only ActionScript.
A native code implementation allows you to reuse existing
For example, you could create a native extension that allows
an application to do the following:
When you have finished your ActionScript and native implementations,
you package your extension. Then, an AIR application developer can
use the package to call your extension’s ActionScript APIs to execute
device-specific functionality. The extension runs in the same process
as the AIR application.
Native extensions versus the NativeProcess ActionScript class
ActionScript 3.0 provides a NativeProcess class. This class
lets an AIR application execute native processes on the host operating
system. This capability is similar to native extensions, which provide
access to device-specific features and libraries. When deciding
on using the NativeProcess class versus creating a native extension,
consider the following:
supports the NativeProcess class. Therefore, for applications with
the AIR profiles
native extensions are the only choice.
Native extension developers often provide native implementations
for various platforms, but the ActionScript API they provide is
typically the same across platforms. When using the NativeProcess
class, ActionScript code to start the native process can vary among
the different platforms.
The NativeProcess class starts a separate process, whereas
a native extension runs in the same process as the AIR application.
Therefore, if you are concerned about code crashing, using the NativeProcess
class is safer. However, the separate process means that you possibly
have interprocess communication handling to implement.
Native extensions versus ActionScript class libraries (SWC files)
The most important difference between a native extension
and a SWC file is that the SWC file contains no native code. Therefore,
if you determine that you can accomplish your goal without native
code, use a SWC file rather than a native extension.
You can create native extensions for the following devices:
Android devices, starting with AIR 3 and Android 2.2.
iOS devices, starting with AIR 3 and iOS 4.0
iOS Simulator, starting with AIR 3.3
Blackberry PlayBook, starting with AIR 2.7
Windows desktop devices that support AIR 3.0
Mac OS X desktop devices that support AIR 3.0
An extension can target multiple platforms. For more information,
Targeting multiple platforms
Supported device profiles
The following AIR profiles support native extensions:
, starting in AIR
, starting in AIR 3.0