How many levels deep can you nest swf's - will 3 work - like child inside parent inside grandparent?

Question

The code at the bottom of this post nests an AS2 "player" inside a Flex app (AS3). Look at the part that says "[AS2 player swf]". That AS2 player swf has almost no code - just one function that loads an asset from a remote server. Very simple:

this.onLoad = function(){
    content.loadMovie("http://URL_TO_REMOTE_SWF");
};

And it has no other assets. Just one MovieClip - "content".

So we've got a Flex app that loads an AS2 swf that loads a remote swf. No dice. Remote swf doesn't load and display. No errors reported.

Important: The AS2 app on its own works. If I go navigate to it in my file system and double click, remote swf does indeed load and display. So I've established that the unwrapped AS2 swf player works and does indeed load remote swf's. Something about nesting that player inside the Flex app creates a problem. Are you not allowed to do this - 3 levels of swf nesting (child - parent - grandparent)?

UPDATE: Target remote swf's load and display fine directly in Flex as well (skipping AS2 swf). So problem doesn't appear to be with AVM1/AVM2 discrepancy between target content and Flex app. Could be AVM1/AVM2 problem with how the Flex app displays the AS2 swf but only when it contains content.loadMovie("http://URL_TO_REMOTE_SWF"). Loads and displays without that line.

UPDATE: This is a Flex packaged IOS application and thus is subject to ActionScript restrictions for dynamically loaded code. But it doesn't work in a regular Flex (non packaged IOS) app either which is not subject to these limitations. THE FOLLOWING CODE SHOULD WORK AS FAR AS I CAN TELL IN A REGULAR FLEX BROWSER BASED APPLICATION.

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
               xmlns:s="library://ns.adobe.com/flex/spark" 
               xmlns:mx="library://ns.adobe.com/flex/mx"
               initialize="init()"> 
    <fx:Script>
        <![CDATA[           
            import mx.core.UIComponent;

            private var request:URLRequest = new URLRequest("[AS2 player swf]");
            private var loader:Loader = new Loader();

            private var myComponent:UIComponent = new UIComponent;  

            private function init():void{
                myComponent.percentHeight = 100;
                myComponent.percentWidth = 100;
                loader.load(request);
                myComponent.addChild(loader);
                player.addElement(myComponent);
            }           
        ]]>
    </fx:Script>

    <s:Group id="player"
             height="100%" width="100%"/>   

</s:Application>

weltraumpirat weltraumpirat · Accepted Answer · 2011-12-21T19:08:15

Since all Sprites and MovieClips are both display objects and display object containers, you could theoretically keep nesting them forever. There are physical restraints, of course, but I see no reason why there should be a limit other than memory and processing power (at some point, refreshing the screen will become sluggish, and eventually painful to wait for).

I've searched the web to see if I could find any information about a built-in limit enforced by the AVM, any documents or error codes that would suggest there is one, but I couldn't find anything at all. Of course, that doesn't mean there isn't - it just means the limit hasn't been reached by many people yet ;)
So if anyone else knows more...

EDIT

Since the information about your loaded MovieClip is new, here's my update: AVM1 (AS1 & 2) SWFs don't always execute in the same way when loaded into an AVM2 (AS3) movie. This has nothing to do with the number of nested display objects. I originally thought this was because the _lockroot property was removed in AS3, but I've searched a bit and found out it is assumed true by default, and should therefore not be a problem.

There may be many things about your scenario that are different from when the file runs on its own, and I would start by looking at these:

Do you use relative path names to load other data into the AS2 swf?
Do you get any error messages (particularly, security sandbox violation errors)?
Does your AS2 SWF rely on external variables to be set (FlashVars)
Does your AS2 SWF need ExternalInterface access?

FINAL EDIT

Since this new info has just come up:

There is absolutely no way to execute dynamically loaded AVM byte code on an iPad at runtime, for the same reason that there is no Java VM and no Flash Player for iOS: Apple does not allow the execution of dynamically loaded byte code at all. Period.

Hence, you can load and play SWF animations, but not ActionScript. It will simply be ignored. Also, neither of the apps that you did run is in fact AVM byte code - they are compiled into LLVM byte code instead.

You will have to find a way to check for the end of the animation that does not involve stop() commands. Perhaps this can be done by checking frame numbers from your AS3 container?

How many levels deep can you nest swf's - will 3 work - like child inside parent inside grandparent?

2 Answers