Accessing displayObjects on the timeline after a gotoAndStop or gotoAndPlay

By scott

I have been meaning to add this to my blog for quite some time now. I have read a few postings related to this topic but I am surprised there aren’t a lot more people complaining about this. Personally I feel Adobe really dropped the ball with this bug. I guess I should explain what the bug is before I go on.

Lets pretend we’re creating a button, now I know most of my readers are developers and for the most part we would never create a simple button like this using multiple frames on the timeline. But we all know that designers love to use the timeline and create button states using frames and frame labels. I actually think this posting will help designers as much as it will help the developers who are working with said designers.

Now lets pretend our button has 3 states, up, over, and down and each state is represented on the timeline, 5 frames apart and the frame is labeled the same as each state. So the first frames label is “up”, the 5th frames label is “over”, and the 10th frames label is “down”. On each frame there is a MovieClip named button and each key frame has the same graphic just tinted differently to differentiate the states. Then on our code layer we set up MouseEvents for each state MOUSE_OVER, MOUSE_OUT, and MOUSE_DOWN, in each of the event handlers we move the playhead to each frame using the gotoAndStop method while passing in the frame label that we want the playhead to move to. Ok, so this is all straight forward. Very flash 4. The interesting part of this is when you try to access sibling displayObjects on the same frame right after we call gotoAndStop.

To illustrate this bug lets add a layer below the layer that has our button on it. On this layer add a keyframe at frame 5 and add a MovieClip, whatever you want, import a picture draw a shape, it doesn’t matter. Just as long as you give it an instance name of overClip. Right after we call gotoAndStop(‘over’) try and trace (overClip). If you are not completely following me right now here is a picture of what my timeline looks like:

And our code will look something like this (excuse the timeline code, but it is the easiest way to demonstrate this bug).

button.addEventListener(MouseEvent.MOUSE_OVER, rollover);
button.addEventListener(MouseEvent.MOUSE_OUT, rollout);

function rollover(e:MouseEvent):void {
     gotoAndStop('over');
     trace('the instance name of the overclip is: ' + this.overClip.name);
}

function rollout(e:MouseEvent):void {
     gotoAndStop('up');
}

In the rollover function you will notice I added a trace that traces out the name property of the overClip that appears on the out frame (or frame 5 for those of you who like numbers). If you were to run this code you will notice that the rollover works, the playhead moves to frame 5 and visually you see the change, however, the trace statement throws the following error “TypeError: Error #1009: Cannot access a property or method of a null object reference.” Null?? How can that be, the playhead is at frame 5, and the overClip is on frame 5, why is overClip null? Good question! The other odd thing is if you trace out numChildren right after the gotoAndStop(‘over’) call it will return the correct number of child displayObjects. How can the player know how many children there is but still throw an error saying we’re trying to access a null object reference?

This was a very common practice in AS2, especially in highly creative sites with both Flash Designers and Flash Developers. And as more creative shops start embracing Flash 9 I think this issue will become more common.

Well, the first thing I thought to do was to call stage.invalidate() before I called gotoAndStop(‘over’), in theory this should force a redraw and fire the render event. Well it did fire the render event but I still couldn’t trace out the clip on frame 5. Arghhh!

The one thing I did notice is the error is only thrown the first time rollover is called. Everytime after that the reference to overClip traces out fine. So this got me thinking. It looks like displayObjects do not register until the current frame cycle is complete. For those who do not know, a frame cycle is two parts, first the code executes, once the code on that particular frame executes any display updates are executed (adding overClip to the timeline is a display update).

The first approach to get around this bug I thought up was to kick off a EnterFrame event in the rollever function, after the EnterFrame event is fired, it still didn’t trace out overClip. Then I thought maybe I need a second frame cycle to register everything because technically the EnterFrame event fires at the exact moment the playhead hits the frame which is exactly the same problem we already have. Ok, so lets allow for two EnterFrame events to fire, kill the event, and trace out overClip. Guess what, that works. Here is the code for this approach.

var count = 0;

button.addEventListener(MouseEvent.MOUSE_OVER, rollover);
button.addEventListener(MouseEvent.MOUSE_OUT, rollout);

function rollover(e:MouseEvent):void {
     count = 0;
     gotoAndStop('over');
     addEventListener(Event.ENTER_FRAME, rolloverDelay);
}

function rolloverDelay(e:Event):void {
     count++
     if (count == 2) {
          removeEventListener(Event.ENTER_FRAME, rolloverDelay);
          trace('the instance name of the overclip is: ' + this.overClip.name);
     }
}

function rollout(e:MouseEvent):void {
     gotoAndStop('up');
}

Yes this works, but imagine how complex this mess of code would get if we had a complex 12 state button with animations on each state. Not very practical.

The only way I could come up with to get around this issue was to create an EnterFrame that fires right off the bat, moves the playhead to the last frame of the timeline, and then returns it to the first frame. This ensures that everything that exists on the last frame will be registered and you will be able to access it immediately following the gotoAndStop(‘over’) call. The key to this approach is only items that are still in the display list on the last frame will register. If you have a blank keyframe after overClip it will not register if the last frame of the timeline is beyond that. Here is the code for this approach.

button.buttonMode = true;
button.addEventListener(MouseEvent.MOUSE_OVER, rollover);
this.addEventListener(Event.ENTER_FRAME, frameentered);
this.addEventListener(Event.RENDER, rendered);

function frameentered(e:Event) {
     this.removeEventListener(Event.ENTER_FRAME, frameentered);
     if (overClip == null) {
          stage.invalidate();
          this.gotoAndStop(totalFrames);
     }
}

function rendered(e:Event):void {
     if (this.currentFrame == this.totalFrames) {
          this.gotoAndStop(1);
     }
}

function rollover(e:MouseEvent):void {
     trace('the instance name of the overclip is: ' + this.overClip.
}

Excellent, we’re making progress. But we are working with a very simple example, a two state button (up and over). What if we had a more complex button, say 4 states (up, over, down, and disabled), and at each state different assets were added to the timeline like so.

I know, I said complex, and this timeline is far from complex, where are all the tweens, and hundreds of layers, guides, and masks. Well, lets just pretend all that fun stuff is there for now.

If we were to try the last approach with this more complex timeline we still wouldn’t have access to the clips on the over and down frames. This is because we moved the playhead from the first frame to the last frame and back to the first frame again. The playhead never touched anything in between so the clips on the over and down frames would not have been registered yet.

The first approach I came up with to register the clips on all the frames was quite innovative, so I thought. Basically I used the currentLabels array property of MovieClip. For those who don’t know, the MovieClip class now contains a currentLabel and a currentLabels property. The currentLabel returns a FrameLabel object if one exists for the current frame that the playhead is currently on. A FrameLabel Object contains two properties, name, and frame. The name property is the frame label name and the frame property is the frame number (int) of the current frame the playhead is on. The currentLabels property of MovieClip returns an array of FrameLabel Objects containing all the FrameLabels for the targeted MovieClip. Using the currentLabels array I thought I could loop through each FrameLabel in the array and move the playhead to each frame label and once it is complete return the playhead back to the first frame. However, you cannot use a traditional for loop because the frame cycle will not occur until the for loop is complete. Instead I set up a counter variable and use an EnterFrame to move through each FrameLabel Object for targeted MovieClip. This approach is very similar to our previous approach with more stops in between. Lets call this approach the milk run. Here is what my code looked like for this approach.

button.buttonMode = true;
var count:int;
if (count == 0) {
     this.visible = false;
     addEventListener(Event.ENTER_FRAME, proxyframes);
     addEventListener(Event.RENDER, rendered);
}

function proxyframes(e:Event) {
     stage.invalidate();
     gotoAndStop(this.currentLabels[count].name);
     trace(this.currentFrame);
}

function rendered(e:Event):void {
     count++
     trace('render called' + this.currentFrame)

     if (count == this.currentLabels.length) {
          init();
          gotoAndStop(1);
          removeEventListener(Event.ENTER_FRAME, proxyframes);
          removeEventListener(Event.RENDER, rendered);
     }
}

function init() {
     this.visible = true;
     button.addEventListener(MouseEvent.MOUSE_OVER, rollover);
     button.addEventListener(MouseEvent.MOUSE_OUT, rollout);
     button.addEventListener(MouseEvent.MOUSE_DOWN, press);
     button.addEventListener(MouseEvent.MOUSE_UP, release);
}

function rollover(e:MouseEvent):void {
     gotoAndStop('over');
     trace(overClip.name);
}

function rollout(e:MouseEvent):void {
     gotoAndStop('up');
}

function press(e:MouseEvent):void {
     gotoAndStop('down');
     trace(downClip.name);
}

function release(e:MouseEvent):void {
     gotoAndStop('disabled');
     trace(disabledClip.name);

     //disable buttons if there was a parent clip parent.mouseChildren = false would also work.
     button.buttonMode = false;
     button.removeEventListener(MouseEvent.MOUSE_OVER, rollover);
     button.removeEventListener(MouseEvent.MOUSE_OUT, rollout);
     button.removeEventListener(MouseEvent.MOUSE_DOWN, press);
     button.removeEventListener(MouseEvent.MOUSE_UP, release);
}

So why doesn’t this work. Well if you remember what I said earlier, moving the playhead only registers the last frame that it was on. If you run this code you will notice the rollover and rollout methods return null but the release method traces out the correct value, this is because that was the last stop on our playhead milk run.

In order for this approach to work I would have to layout my timeline appropriately. Each state clip should be on its own layer with nothing after it (including blank keyframes) on the timeline, like so:

Now you will notice that the above code works, we are now able to trace out the extra clips that appear on each frame with a label. However, now that everything exists on the last frame we really don’t need to loop through each FrameLabel to register the clips, we can just use our first trick and move the playhead to the last frame, once it renders move back to the first frame. Even though the looping through the FrameLabels code is overkill for this example I thought I would keep it in so people know that capability exists.

So we are able to access sibling displayObjects now but there still is one functional issue. Since the frames are cascading on the timeline when the playhead is on the down frame both downClip and overClip are visible. Likewise, when the playhead is on the disabled FrameLabel upClip, downClip, and disabledClip are visible. That little bug is not going to slip by the creative department. Normally we would get around this issue by adding blank keyframes on the frame following where the extra clip was displayed. If we were to do this in our example the clips wouldn’t register because they do not exist on the last frame and we would be right back where we started. There are two ways around this, one involves more code (the developer approach), the other involves more keyframes (the designer approach). Both are valid.

The timeline approach basically consists of adding keyframes (not blank keyframes) on the frame after the frame where the extra clip appears and setting the alpha of the clip on the second frame to 0. This ensures that the clip is still on the display list in the last frame and allows it to register. With this approach your timeline would now look like so:

Depending on what else is happening in your application this approach may not work. This is when you have to resort to code (yay). Basically with code we do the same thing, however, instead of simply setting the alpha to 0 we’ll set the visibility to false. This only requires three extra lines of code which are included below.

stop();

button.buttonMode = true;
var count:int;
if (count == 0) {
     this.visible = false;
     addEventListener(Event.ENTER_FRAME, proxyframes);
     addEventListener(Event.RENDER, rendered);
}

function proxyframes(e:Event) {
     stage.invalidate();
     gotoAndStop(this.currentLabels[count].name);
     //gotoAndStop(this.totalFrames);
     trace(this.currentFrame);
}

function rendered(e:Event):void {
     count++
     trace('render called' + this.currentFrame)

     if (count == this.currentLabels.length) {
          init();
          gotoAndStop(1);
          removeEventListener(Event.ENTER_FRAME, proxyframes);
          removeEventListener(Event.RENDER, rendered);
     }
}

function init() {
     this.visible = true;
     button.addEventListener(MouseEvent.MOUSE_OVER, rollover);
     button.addEventListener(MouseEvent.MOUSE_OUT, rollout);
     button.addEventListener(MouseEvent.MOUSE_DOWN, press);
     button.addEventListener(MouseEvent.MOUSE_UP, release);
}

function rollover(e:MouseEvent):void {
     gotoAndStop('over');
     trace(overClip.name);
}

function rollout(e:MouseEvent):void {
     gotoAndStop('up');
}

function press(e:MouseEvent):void {
     overClip.visible = false;
     gotoAndStop('down');
     trace(downClip.name);
}

function release(e:MouseEvent):void {
     gotoAndStop('disabled');
     trace(disabledClip.name);
     overClip.visible = false;
     downClip.visible = false;
     button.buttonMode = false;
     button.removeEventListener(MouseEvent.MOUSE_OVER, rollover);
     button.removeEventListener(MouseEvent.MOUSE_OUT, rollout);
     button.removeEventListener(MouseEvent.MOUSE_DOWN, press);
     button.removeEventListener(MouseEvent.MOUSE_UP, release);
}

That’s it. Adobe, if you are reading this, please, please, please fix this bug. It is very annoying. It is obvious that Flash Player 9 was built with Flex in mind (aka no timeline) since that is all that was available when Flash Player 9 was released. I remember reading someone from Adobe admitting that on their personal blog, if I can find the link again I will post it in the comments below. I covered a lot here, but this bug goes even further. Sometimes Event.RENDER doesn’t even fire. In another related bug stop events on the first frame of nested MovieClip do not always work. Supposidly Adobe fixed this in version 9.0.45 of the player but as you can see by the comments on Emmy’s blog posting about the 9.0.45 release it was never really fixed. In fact we ran into this issue at work recently in the latest 9.0.115 version of the player.

I actually met with the Adobe Flash Player team last week and we discussed a lot of these issues, hopefully they will take these into consideration for the next release. To a developer they may seem like minor issues but designers and animators are going to have a difficult time getting around a lot of these bugs. If anyone else has any workarounds please feel free to explain them in the comments below.

P.S. this is my longest post ever, yay me.

Finally, Yahoo releases Maps API in Actionscript 3

By scott

Better late then never right? For about a year and a half, maybe even 2 years now, developers have been requesting an Actionscript 3 Yahoo Maps API. To cool the fires I wrote the Yahoo Maps Communication Kit, which was a hack that allowed you to use the Actionscript 2 Yahoo Maps component in an Actionscript 3 application. I am glad to say that the Maps communication kit is no longer needed. Head on over to the Yahoo Flash Developer center and download the real Yahoo AS3 Maps Component.

The component looks great, out of the gate I did notice one bug though. They didn’t account for the MOUSE_LEAVE event. You can see this bug in this example, start dragging the map and move the your cursor outside of the map, if you release your mouse while you are still outside of the map and move your cursor back into the map you will notice the map is still moving. A very minor bug. I can’t wait to use this component. I already have a few ideas where I can use it.

Thanks Yahoo! Let’s hope this doesn’t turn into the Microsoft Live Maps AS3 component

onDragOver, onDragOut, and onReleaseOutside in ActionScript 3.0 (AS3)

By scott

In AS2 there were three mouse events that I used quite often. onDragOver was thrown when the mouse button is selected and the cursor was moved over a MovieClip. This was useful to detect if another object was being dragged over a given clip. onDragOut was the opposite, this event was thrown when the mouse button was selected and the cursor was dragged outside of a given clip. And lastly, onReleaseOutside was thrown when a clip was pressed and the user dragged off the clip before releasing the mouse button. Releasing the mouse outside is a common way for a user to bail out of selecting a button among other reasons.

If you look through the AS3 documentation you will notice there are no MouseEvent.DRAG_OVER, MouseEvent.DRAG_OUT, or MouseEvent.RELEASE_OUTSIDE events. This does not mean that this functionality is not available, it’s just not as obvious. The following code shows how to recreate this functionality in AS3.

var button:Sprite = new Sprite();
button.graphics.beginFill(0x000000, 1);
button.graphics.drawRect(50,50,200,100);
addChild(button);

button.buttonMode = true;
button.addEventListener(MouseEvent.MOUSE_DOWN, buttonPress);
button.addEventListener(MouseEvent.MOUSE_UP, buttonRelease);
button.addEventListener(MouseEvent.MOUSE_OVER, buttonOver);
button.addEventListener(MouseEvent.MOUSE_OUT, buttonOut);

function buttonPress(e:MouseEvent):void {
     //the button is pressed, set a MOUSE_UP event on the button's parent stage
     //to caputre the onReleaseOutside event.
     button.parent.stage.addEventListener(MouseEvent.MOUSE_UP, buttonRelease);
}

function buttonRelease(e:MouseEvent):void {
     //remove the parent stage event listener
     button.parent.stage.removeEventListener(MouseEvent.MOUSE_UP, buttonRelease);

     //if the events currentTarget doesn't equal the button we
     //know the mouse was released outside.
     if (e.currentTarget != button) {
          trace('onReleasedOutside');
     } else {
          //the events currentTarget property equals the button instance therefore
          //the mouse was released over the button.
          trace('onRelease');
     }
}

function buttonOver(e:MouseEvent):void {
     if (e.buttonDown) {
          //if the mouse button is selected when the cursor is
          //over our button trigger the onDragOver functionality
          trace('onDragOver');
     } else {
          //if the mouse button isn't selected trigger the standard
          //onRollOver functionality
          trace('onRollOver');
     }
}

function buttonOut(e:MouseEvent):void {
     if (e.buttonDown) {
          //if the mouse button is selected when the cursor is
          //moves off of our button trigger the onDragOut functionality
          trace('onDragOut');
     } else {
          //if the mouse button isn't selected trigger the standard
          //onRollOut functionality
          trace('onRollOut');
     }
}

So let me explain what is going on here.

To recreate the onDragOver and onDragOut functionality we use the buttonDown property of the MouseEvent. The buttonDown property is a Boolean value that indicates if the users mouse button is selected when the event was triggered. If this property is true we know the user is dragging over or dragging out of the button. If the buttonDown property is false we can trigger our standard rollOver or rollOut functionality.

Recreating the onReleaseOutside functionality is a trickier multi-step process. First we must set up a MouseEvent.MOUSE_DOWN event listener on the button. Secondly we set up a MouseEvent.MOUSE_UP event listener on the same button. Third, in the MouseEvent.MOUSE_DOWN event handler we set up another MouseEvent.MOUSE_UP event listener on the button’s stage that triggers the same event handler as the MouseEvent.MOUSE_UP event handler (buttonRelease) that is set on the button. And lastly we check the currentTarget property of the event passed into the MouseEvent.MOUSE_DOWN event handler to see if it equals the button or the button’s parent stage. If the currentTarget equals the button we know the mouse button was released over the button and we can trigger the onRelease functionality. If the currentTarget property isn’t the button we can assume the user released the mouse button outside of the button. Each situation is different, button.parent.stage may not work in your application, you may have to traverse up the display list, possibly right down to the root child (the Stage) to succesfully detect the onReleaseOutside event. Below I have updated the buttonDown method to show a simple way of traversing up the display list as far as you can go and setting the MouseEvent.MOUSE_UP on the root child.

function buttonPress(e:MouseEvent):void {
     //the button is pressed, set a MOUSE_UP event on the root child in the display list
     //to caputre the onReleaseOutside event.
     var rootChild:DisplayObject = button;
     while (rootChild.parent != null) {
          rootChild = rootChild.parent;
     }
     rootChild.stage.addEventListener(MouseEvent.MOUSE_UP, buttonRelease);
}

Enjoy!

AS3 Garbage Collection, the reason your tweens are ending early.

By scott

Josh Tynjala and I were speaking today, well actually typing over IM. We were discussing a problem we both ran into recently, the fl.transitions.Tween class was not dispatching events consistently. Sometimes the TweenEvent.MOTION_FINISH event would be broadcasted, other times it would not. Sometimes our programmatic tweens were visually completing, other times they would not, in a few cases they wouldn’t even start. After a little debugging we realized that the AS3 Garbage Collection was killing the tweens. You may be asking why would the garbage collection be doing this? Let’s start out by looking at some example code.

var len:int = _model.getNumberOfItems();
for (var i:int = 0;i<len;i++)>
     var clip:MovieClip = _scope.getChildByName('button'+i);
     var myTween:Tween = new Tween(clip, 'alpha', Regular.easeOut, 0, 1, 0.5, true);
     myTween.addEventListener(TweenEvent.MOTION_FINISH, buttonAnimationComplete);
}

Pretty simple code, in my AS2 days I used code similar to this a million times and never had a problem. All I am doing is looping through a set number of MovieClips and fading them up from 0 to 100%. Most times this worked fine, but a few times the tweens never completed and buttonAnimationComplete was not called. This is because the AS3 Garbage Collection was deleting the Tweens just like it should be. What? The tweens should be deleted? Yes.

Notice that I am storing the reference to my tween in a local variable that gets overridden in every iteration of the loop. This means there is no real reference to the object and when there is no reference to an object it is flagged for removal by the garbage collector. Since there is no real way to know when the garbage collection cycle is going to run the tweens were completing some of the time and other times were being thrown into the back of the big garbage truck that slowly creeps around your code.

The best way to ensure that this doesn’t happen is to store your reference in a class level member. I ended up storing all of my tween references in a class level array. Once all of the tweens were complete I cleared the array. Here is the updated code that I used, the entire class is not shown here, trust me your scroller will thank me.

private var _buttonTweens:Array = new Array();
private var _buttonTweenCompleteCount:int;

private function animateButtons():void {
     var len:int = _model.getNumberOfItems();
     for (var i:int = 0;i<len;i++)>
          _buttonTweens.push(new Tween(clip, 'alpha', Regular.easeOut, 0, 1, 0.5, true));
          _buttonTweens[_buttonTweens.length - 1].addEventListener(TweenEvent.MOTION_FINISH, buttonAnimationComplete);
     }
}

private function buttonAnimationComplete(e:TweenEvent):void {
     buttonTweenCompleteCount++
     if (buttonTweenCompleteCount == _model.getNumberOfItems()) {
          _buttonTweens = [];
          dispatchEvent(new Event('buttonsReady'));
     }
}

I am just using Tweens as an example, but you can run into this same issue with any object that has local references that are overridden. For example, I had a Timer event set to iterate every 100 milliseconds and it called loadAsset(), a method that did just what it says, it loaded an asset.

private function loadAsset():void {
     _currentItemToLoad++;
     var myLoader:Loader = new Loader();
     myLoader.addEventListener(Event.COMPLETE, assetLoaded);
     myLoader.load(new URLRequest('images/galleryImage' + currentItemToLoad + '.jpg'));
}
private function assetLoaded(e:Event):void {
     var holder:Sprite = new Sprite();
     holder.visible = false;
     holder.addChild(e.target.content);
     _scope.addChild(holder);

     e.target.removeEventListener(Event.COMPLETE, assetLoaded);
}

Just like the Tween example above my Event.COMPLETE event was not firing all the time. This is because I was storing the reference to the Loader in a local variable that was overridden each time the loadAsset method was called. To get around this I stored all my references in a class level member (an object or an array work nicely).

Hopefully this helps you figure out why you are not seeing certain events in your code, it had me stumped for a bit. Now you know, and as G.I. Joe said “knowing is half the battle”.

Grant Skinner’s OSX Squeeze Effect in AS3

By scott

First off, thank you Grant for releasing the source for your squeeze effect. Dirty code is better than no code. After looking at the source code I began to wonder how much better it would run in AS3 so I converted it. I didn’t clean up any of the code, just a straight conversion. It seems to run a little smoother. Next I am going to make it dynamic allowing you to load in an image passed in through flashVars. Maybe if I’m really bored I will set it up so you can load in multiple images from an xml file and build a gallery type app using this effect. Again, thanks Grant, as always, very cool work!

 
Download the rough AS3 source here.
 

Accessing document class of an externally loaded swf with AS3

By scott

I have seen a lot of posts lately with people asking how they can access variables and methods in an external swf that is loaded at runtime using AS3. This isn’t a difficult task, but it is much different than AS2/AS1 where you could just call directly into the loaded swf using the instance chain if you were in the same security sandbox.

First off, lets create our swf that wil be loaded in at runtime. Open up your favourite actionscript editor and create a new class with the following code.

package com.scottgmorgan {
     import flash.external.ExternalInterface;
     import flash.display.Sprite;
     public class ExternalMovie extends Sprite {
          public function ExternalMovie():void {
               //nothing in our constructor right now.
          }
          public function alert(msg:String):void {
               trace(msg);
               ExternalInterface.call('alert', msg);
          }
     }
}

Now create a new FLA and set the above class as the document class. If you are not sure how to do this simply enter the class path (com.scottgmorgan.ExternalMovie) into the document class textfield found in the property panel. Lather, rinse, repeat, compile.

Next we will create the swf that will load our ExternalMovie swf we just created. Let’s jump back to our favourite actionscript editor and create a new class with the following code.

package com.scottgmorgan {
     import flash.display.Loader;
     import flash.net.URLRequest;
     import flash.events.Event;
     import flash.display.LoaderInfo;
     import flash.display.Sprite;
     public class SourceMovie extends Sprite {
          public function SourceMovie():void {
               var loader:Loader = new Loader();
               loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onLoadComplete);
               loader.load(new URLRequest('ExternalMovie.swf'));
          }
          private function onLoadComplete(e:Event):void {
               var loaderInfo:LoaderInfo = e.target as LoaderInfo;
               addChild(e.target.content);
               var swf:Object = loaderInfo.content;
               swf.alert('Hello World');
          }
     }
}

That’s it, LoaderInfo saves the day. LoaderInfo.content connects you with the document class of the externally loaded swf. Lets create a new FLA, assign the SourceMovie class as the document class and compile. Make sure the SourceMovie.swf and ExternalMovie.swf are in the same directory. The as files should be in /com/scottgmorgan/. Let’s compile the SourceMovie and you should see “Hello World” in the output window if you run the swf inside the IDE, if you run it from a browser you should see an alert dialog with “Hello World”.

Another option you have is to use the ApplicationDomain class. Using the ApplicationDomain class you can add the classes from the ExternalMovie to the SourceMovie’s ApplicationDomain. This is a great way to load in code libraries at runtime.

Lets pretend we have a large application with multiple levels of security, maybe we are creating a content management system and we need multiple permission levels. User A can only update content, User B can update content and update the site map, User C is an administrator and can do everything User A and B can do but can also access tracking information, edit user profiles, update permissions, etc. When User B logs in the application loads the site map code library (sitemapadmin.swf) and adds its classes to the main ApplicationDomain. When User C logs in the sitemapadmin.swf classes would be added to the main ApplicationDomain, for this user the application would also load the trackingadmin.swf, and useradmin.swf code libraries and add all the included classes to the main ApplicationDomain.

Let’s update our SourceMovie.as file and add the ExternalMovie class to SourceMovie’s ApplicationDomain.

package com.scottgmorgan {
     import flash.display.Loader;
     import flash.net.URLRequest;
     import flash.events.Event;
     import flash.display.LoaderInfo;
     import flash.display.Sprite;
     import flash.system.ApplicationDomain;
     public class SourceMovie extends Sprite {
          public function SourceMovie():void {
               var loader:Loader = new Loader();
               loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onLoadComplete);
               loader.load(new URLRequest('ExternalMovie.swf'));
          }
          private function onLoadComplete(e:Event):void {
               ApplicationDomain.currentDomain.getDefinition("com.scottgmorgan.ExternalMovie");
               var myExternalMovie:ExternalMovie = ExternalMovie(e.target.content);
               myExternalMovie.alert('Hello World');
          }
     }
}

There you have it. One thing you will notice is you don’t have to add the loaded swf to the display list to access its classes. Hopefully you will be able to use these techniques in future projects.

Say hello to my little friend – describeType()

By scott

It amazes me that people don’t know about describeType(). If you’re lazy, or as some developers call it, efficient, you always don’t have time, or really don’t feel like digging through half assed completed documentation to see what parameters a classes constructor accepts. Sounds like the perfect time to combine forces, trace() meet flash.utils.describeType(). The describeType() method returns an xml dump that contains all the details you’d ever need to know about any object that is passed in as a parameter.For example, let’s pretend this is our first time working with Flash (of course you could be working in Flex too), lucky us, we never had to use AS2 or AS1, we only heard our cubicle neighbors groaning about spaghetti code, and hidden code attached to buttons. Since this is our first time using Flash we don’t even know what a MovieClip is or what methods are available to us. One simple line of code will solve our ignorance.

trace(flash.utils.describeType(flash.display.MovieClip));

This one little line of code returns this to us in our output window (shortened for your scroll wheels sake):

<type name="flash.display::MovieClip" base="Class" isDynamic="true" isFinal="true" isStatic="true">  <extendsClass type="Class"/>  <extendsClass type="Object"/>  <accessor name="prototype" access="readonly" type="*" declaredBy="Class"/>  <factory type="flash.display::MovieClip">    <extendsClass type="flash.display::Sprite"/>    <extendsClass type="flash.display<::DisplayObjectContainer"/>    <extendsClass type="flash.display::InteractiveObject"/>    <extendsClass type="flash.display::DisplayObject"/>    <extendsClass type="flash.events::EventDispatcher"/>    <extendsClass type="Object"/>    <implementsInterface type="flash.display::IBitmapDrawable"/>    <implementsInterface type="flash.events::IEventDispatcher"/>    <accessor name="scenes" access="readonly" type="Array" declaredBy="flash.display::MovieClip"/>    <method name="stop" declaredBy="flash.display::MovieClip" returnType="void"/>    <method name="nextScene" declaredBy="flash.display::MovieClip" returnType="void"/>    <method name="play" declaredBy="flash.display::MovieClip" returnType="void"/>    <accessor name="currentScene" access="readonly" type="flash.display::Scene" declaredBy="flash.display::MovieClip"/>    <accessor name="currentFrame" access="readonly" type="int" declaredBy="flash.display::MovieClip"/>    <accessor name="trackAsMenu" access="readwrite" type="Boolean" declaredBy="flash.display::MovieClip"/>    <method name="gotoAndStop" declaredBy="flash.display::MovieClip" returnType="void">      <parameter index="1" type="Object" optional="false"/>      <parameter index="2" type="String" optional="true"/>    </method>    <accessor name="currentLabels" access="readonly" type="Array" declaredBy="flash.display::MovieClip"/>    <method name="willTrigger" declaredBy="flash.events::EventDispatcher" returnType="Boolean">      <parameter index="1" type="String" optional="false"/>    </method>  </factory></type>

The output window never looked so good. Methods, paramaters, superclasses, accessors, the amount of information that is returned is beautiful. I don’t know how many for in loops I wrote in AS2 just to try and figure out what methods were available in a custom class.One thing to note is that describeType() only shows public properties and methods, and will not show properties and methods that are private, package internal or in custom namespaces.If you have never looked at the flash.utils.* package, I suggest you do, there are some handy little utilities in there.

Yahoo launches new Flash Blog and new Flash and Flex Libraries

By scott

Well this will probably be my last posting that announces something my team (Yahoo! Flash Platform) at Yahoo has launched. From now on it will be my former team as I am leaving to work for Disney on Friday. This week we launched three very exciting things. The new Yahoo! Flash Platform blog (http://www.yswfblog.com), the new and improved Yahoo! Flash Development Center (http://developer.yahoo.com/flash) and our new Astra Flash Components. The Astra Library is our collection of Flash and Flex components, libraries and toolkits. In this inaugural release, ASTRA contains five UI components that complement the existing set provided with Flash CS3. The new UI components are: Tree, Menu, TabBar, AutoComplete, and Charts. ASTRA is open-source under the BSD license, and follows an approach similar to the very popular YUI Library. Keep an eye on the ASTRA library, I know first hand that there are some very cool things to come.

Yahoo! Actionscript 3 API Library launched today.

By scott

I am proud to announce the new Yahoo! AS3 Libraries that were released today on the Yahoo! Flash Developer Network. We timed this launch with the 360Flex conference in San Jose at the Ebay campus. I will be presenting the Yahoo! AS3 Maps Commuication Kit tomorrow morning. As a side note this is my first contribution to the Yahoo Developer Network since I started here a couple months ago. Let us know what you think, and what else you would like to see. We’re here to make your job easier. We don’t want you to worry about accessing all of our data, we want you to concentrating on creating the best application with our data.

Happy Mashing!

Let them know we want a Yahoo! Maps AS 3.0 API.

By scott

Those interested in a Flex 2 Yahoo! Maps API, you have a collective voice. Someone created a suggestion queue here: http://suggestions.yahoo.com/detail/?prop=ydn&fid=3208 I can’t say for sure if this will convince the powers that be to go ahead with this initiative, but supply is based on demand. So go vote and let your desire to have a true Flex 2 Yahoo! Maps API be heard.

As Chuck Freedman said, “together, we can change the world& or least how we add it to our Flex 2 applications”.