Implementing the FREFunction interface

The AIR runtime uses the FREFunction interface to invoke your Java functions from ActionScript code. Implement this interface to expose a concrete piece of functionality.

The FREFunction interface defines a single method, call() . This method is called by the AIR runtime when ActionScript code in the extension invokes the call() method of the ExtensionContext class. To find the right FREFunction instance, the runtime looks in the FREContext function map. The ActionScript code passes an array of arguments to the method using the normal ActionScript types and classes for the arguments. Your Java code sees these values as FREObject instances. Likewise, your Java call() method returns an FREObject instance and the ActionScript code sees the return value as an ActionScript type.

When you implement an FREFunction class, you decide on the order of the parameters in the call() method arguments array. Since you also write the ActionScript side, you use that same parameter order in the ExtensionContext instance’s call() method. Therefore, although every Java function parameter is an FREObject type, you know its corresponding ActionScript type.

Similarly you decide on the ActionScript type of the return value, if any, of a Java function. The call() method returns an object of this type. Although the Java function return value is always an FREObject instance, you know its corresponding ActionScript type.

The FREObject instances created by or passed to an FREFunction object have limited valid life spans. Do not save references to FREObjects between function invocations.

FREFunction example

The following example illustrates a simple FREFunction implementation. The function takes a boolean parameter and returns its negation.

package com.example; 
 
import com.adobe.fre.FREContext; 
import com.adobe.fre.FREFunction; 
import com.adobe.fre.FREObject; 
 
import android.util.Log; 
 
public class UsefulFunction implements FREFunction { 
    public static final String KEY = "usefulFunctionKey"; 
    private String tag; 
 
    public FREObject call(FREContext arg0, FREObject[] arg1) { 
        ExtensionContext ctx = (ExtensionContext) arg0; 
        tag = ctx.getIdentifier() + "." + KEY; 
        Log.i( tag, "Invoked " + KEY ); 
        FREObject returnValue = null; 
 
        try { 
            FREObject input = arg1[0]; 
            Boolean value = input.getAsBool(); 
            returnValue = FREObject.newObject( !value );//Invert the received value 
 
        } catch (Exception e) { 
            Log.d(tag, e.getMessage()); 
            e.printStackTrace(); 
        } 
        return returnValue; 
    } 
}