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We have mentioned the Extension Context a few times already:
- when we saw how ActionScript and native code communicate;
- when we talked about the Extension Initializer and Finalizer;
- when we looked at the Extension Initializer and Finalizer implementations in C and in Java.
I reckon it’s time to look at what actually an Extension Context is. Agreed?
It’s a middleman
You can think of the Extension Context as the middleman between ActionScript and Native code. It’s like a tour guide that speaks both languages and helps the two sides communicate with one another.
You can have one or more Extension Context instances in your native extension.
Extension Context on the ActionScript side
In ActionScript an Extension Context is an instance of flash.external.ExtensionContext. Its role is to allow your ActionScript code to do the following:
- create one or more instances of the Extension Context:
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import flash.external.ExtensionContext; var m_extensionContext : ExtensionContext; m_extensionContext = ExtensionContext.createExtensionContext(EXTENSION_ID, null); |
- call native functions:
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m_extensionContext.call( "as_reverseArrayInPlace", _array ); |
Here as_reverseArrayInPlace is the name of a function that is implemented in your native library and _array is an argument that this function takes. We will see how native functions are implemented and made available to ActionScript in a future post.
- receive events sent from native code:
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m_extensionContext.addEventListener( StatusEvent.STATUS, onStatusEvent ); private function onStatusEvent( _event : StatusEvent ) : void { trace( _event.code ); trace( _event.level ); } |
Extension Context on the native side
In your native code the Extension Context masquerades as an instance of FREContext. It’s the first thing that gets created when your extension is loaded and the Extension Initializer is called.
The C version of FREContext is defined as
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typedef void * FREContext; |
In Java, unsurprisingly, FREContext is a class that you have to implement:
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import com.adobe.fre.FREContext; public class SpeechRecognizerContext extends FREContext; {...} |
What’s next?
Next we will see how the Extension Context is created, initialized and destroyed.
Then we will have a look at an ActionScript example of handling the extension context.
Over to you
Which programming language do you use for the native code in your ANEs?
The ExtensionContext class is not available to me. The only thing available to me in the flash.external class is flash.external.ExternalInterface.
I’ve tried with AIR24 as well as Flex 4.15.0 + AIR23. I’m using FlashDevelop and trying to build a library for an ANE, following your tutorial and your sample project I downloaded.
I was able to access ExtensionContext when building the project in FlashBuilder, as per your tutorial, so looks like it’s an Adobe imposed limitation.