Stronger Together: Developing an Organizational Strategy for Accessible Desig...
AFPS_2011
1. Flash Runtime Native Extensions
Building AIR apps with native capabilities
Rajorshi Ghosh Choudhury Syed Mohd Mehadi
Computer Scientist Lead Software Engineer
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2. What are native extensions?
Third-party, native-code backed ActionScript API
additions to AIR applications
Flash Builder
Android SDK & NDK
AIR SDK
XCode
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3. Who needs them anyway…
• Adobe AIR is awesome
– Allows you to create cross platform applications
– Rapid multiscreen development
– A large feature set (Accelerometer, Geolocation, Gestures and more)
• But…
– No access to some device specific capabilities (Contacts, Bluetooth, etc)
– Waits for a native feature to mature before providing access to it
– Porting existing native applications to AIR might be a pain
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4. Bridging the gap
• Provides access to device specific features
• Native developers can reuse existing code
• AS API set can be extended
• Same interface can be used on different platforms
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5. Anatomy of an extension
• A set of ActionScript classes
• Associated native code for one or more target
devices
• A descriptor that contains deployment information
• A signature to ensure secure delivery (optional)
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6. Accessing the native code
Creating the Extension Context
• A context object binds the ActionScript and native halves of
an extension.
• Calls to native functions happen within a context.
• There may be multiple extension context objects.
import flash.external.ExtensionContext;
...
var ctx : ExtensionContext =
ExtensionContext.createExtensionContext(“com.sample.myExtension", “basicType");
var str : String = ctx.call(“myNativeFunction") as String;
...
ctx.dispose();
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7. Writing the native code
• Use either C or Java APIs
• APIs are mostly cross-platform
• Can be multi-threaded
• Compiled into static or dynamic libraries depending on
target platform
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8. Writing the native code
Initializing and finalizing the extension
• Extension Initializer
– Called when the first extension context is created.
typedef void (*FREInitializer)(
void** extDataToSet ,
FREContextInitializer* ctxInitializerToSet,
FREContextFinalizer* ctxFinalizerToSet );
• Extension Finalizer
– Called (if and) when extension is unloaded.
typedef void (* FREFinalizer)(
void** extDataToSet);
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9. Writing the native code
Initializing and finalizing the context
• Context Initializer
– Called every time a new extension context is created.
– Registers native functions to be called in this context.
typedef void (*FREContextInitializer)(
void** extDataToSet ,
const uint8_t* ctxType,
FREContext ctx,
uint32_t* numFunctionsToSet,
const FRENamedFunction** functionsToSet);
• Context Finalizer
– Called when an extension context is disposed.
typedef void (* FREContextFinalizer)(
FREContext ctx);
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12. Multi-threading support
Threading
• Native libraries may be multi-threaded
• Native calls are serialized
• All functions in the API except one can be called only from a
thread on which a registered function is in progress.
• Only function that can be called from any thread is
FREDispatchStatusEventAsync()/FREContext.DispatchStatusEventAsy
nc()
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13. Describing the Extension
The extension descriptor
<extension xmlns="http://ns.adobe.com/air/extension/2.5">
<id>com.sample.myExtension</id>
<version>1</version>
<platforms>
<platform name="Android-ARM">
<applicationDeployment>
<nativeLibrary>MyExtension.jar</nativeLibrary>
<initializer>com.example.MyExtension</initializer>
</applicationDeployment>
</platform>
<platform name="MacOS-x86">
<applicationDeployment>
<nativeLibrary>MyExtension.framework</nativeLibrary>
<initializer>InitMyExtension</initializer>
<finalizer>FiniMyExtension</finalizer>
</applicationDeployment>
</platform>
<!-- Hypothetical example of a possible Digital Home platform -->
<platform name="Samsung-MIPS">
<deviceDeployment/>
</platform>
<!-- Optional default impl -->
<platform name="default">
<applicationDeployment/>
</platform>
</platforms>
</extension>
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16. Java API List
interface FREExtension {
public static native FREObject newObject ( String
void initialize ();
className, FREObject constructorArgs[]);
FREContext createContext( String contextType); }
void dispose ();
}
public class FREBitmapData extends FREObject {
public static FREBitmapData newBitmapData (int width, int
public abstract class FREContext {
height, boolean transparent, Byte[] fillColor);
public abstract Map<String,FREFunction> getFunctions();
public int getWidth();
public FREObject getActionScriptData();
public int getHeight() ;
public void setActionScriptData( FREObject object );
public java.nio.ByteBuffer getBits();
public abstract void dispose();
public void acquire();
public void dispatchStatusEventAsync( String code,
String level );
void invalidateRect( int x , int y , int width , int height );
} }
interface FREFunction { public class FREByteArray extends FREObject {
FREObject call( FREContext ctx, FREObject[] args ); public static FREByteArray newByteArray ();
} public long getLength();
public java.nio.ByteBuffer getBytes();
public class FREObject { public void acquire();
public static FREObject newObject ( int value ); public void release();
public static FREObject newObject ( double value ); }
public static FREObject newObject ( boolean value );
public static FREObject newObject ( String value ); public class FREArray extends FREObject {
public int getAsInt (); public double getAsDouble(); public static FREArray newArray (String classname, int
public bool void setProperty( String propertyName, FREObject numElements, boolean fixed);
propertyValue );
public static FREArray newArray (int numElements);
FREObject callMethod( String methodName,
public long getLength();
FREObject methodArgs[] );
public void setLength( long length );
getAsBool ();
public FREObject getObjectAt( long index );
public String getAsString();
public void setObjectAt( long index, FREObject value );
FREObject getProperty( String propertyName );
}
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