AS3 Events Explained: Using Event Listeners

Good tips Thanks

very well explained.
thanks

I have a .fla template that I use to remove a video layer once the transparent greeter has played through. It was written is AS2. Thanks to the ease of dragging player controls onto the stage in AS3 I would like to replace this stop listener with identical AS3 code. I’m a virtual beginner with Flash CS3 and to date haven’t been able to accomplish it. This is the AS2 code:

import flash.external.*;

var fired:Boolean = false;

var stopListener:Object = new Object();
stopListener.stopped = function(eventObject:Object):Void
{
    trace("stopped");
    if (!fired)
    {
        ExternalInterface.call("onVidStop");
        fired = true;
    }
};
flvpb.addEventListener("stopped", stopListener);
</pre>

A commonjs.js file reacts to the stop and removes the layer. I don't know enough to know whether or not you'd need to see that to be sure of the same result, but I doubt it. If you can help in any way I'd be grateful.

David in Toronto

Hi Michael,

Thanks for the post; I’m just trying to come to grips with events in AS3. One problem I am facing is knowing when an event / eventhandler has been trigged inside of a class.

ie. this class performs some actions and once all external data is loaded, triggers an event

DatabaseConnection .as

public class DatabaseConnection {
...
loader.addEventListener(Event.COMPLETE,completeHandler);

private function completeHandler(event:Event):void {
trace("All data is loaded!");
}
...
}

Then in the main class I need to know when completeHandler has been triggered

Main .as

var DB:DatabaseConnection=new DatabaseConnection();

// accessing a property of DB returns null as it hasn't loaded yet...
// has the event completed in the DatabaseConnection class yet?

Any thoughts on how this can be achieved?
Cheers
Ryan

Hey Michael, I apologize for disappearing after posting my question on stopListeners in AS3. To your question I’m coding on the timeline and it is the end of the video (FLVPB) that triggers the “stopped” event. For reference we’re going back to January 26th in this thread.

David

To Ryan:
Make sure that the addEventListener in your Main.as is listening to the same event object type as your clone.

For example:
If I were to dispatch a TimerEvent.TIMER_COMPLETE in my DatabaseConnection.as completeHandler( ), the Main.as should have an addEventListener listening to TimerEvent.TIMER_COMPLETE (it must be the same, else it will fail)

I have tested this (e.clone) and it works for me

if you want to try, below is a simple code:-

Main.as

package

{
import flash.display.Sprite;
import flash.events.Event;
import flash.events.TimerEvent;

public class Main extends Sprite 
{   
    public function Main():void 
    {
        var myTimer:MyTimer = new MyTimer();
        myTimer.addEventListener(TimerEvent.TIMER_COMPLETE, timerHandler);
        myTimer.start();
    }

    private function timerHandler(e:Event):void
    {
        trace("Event Clone");
    }
}

}

MyTimer.as

package

{
    import flash.events.Event;
    import flash.events.EventDispatcher;
    import flash.events.TimerEvent;
    import flash.utils.Timer;

public class MyTimer extends EventDispatcher
{

    private var timer:Timer = new Timer(50,1);

    public function MyTimer() 
    {
        super();
        this.timer.addEventListener(TimerEvent.TIMER_COMPLETE, this.timerHandler);
    }

    public function start():void
    {
        this.timer.start();
    }

    private function timerHandler(e:TimerEvent):void
    {
        super.dispatchEvent(e.clone());
    }

}

}

Hi Ayu,

I referenced ‘Event.COMPLETE’ in both classes and it did not seem to fire the event. Perhaps the event needs to be cast to an explicit type? I’m not sure. There could also have been another reason why the event was not firing.

I will try to play around with it when I get some more free time. For now the custom event is working =) Thanks Ayu and Michael.

Hi, excellent to have complicated things explained so simple!

Have a question about the scoop of a variable, when handling EventListeneres:
How can fTwo access variable a accessible to fOne?

        function fOne() 
        {
            var a:int = 0;
            this.addEventListener(someEvent, fTwo);
        }

     function fTwo(e:Event):void
    {
        trace (a);
    }

may/ should/ can I use this instead? Is this valid? Is any better?

        function fOne() 
        {
            var a:int = 0;
            this.addEventListener(someEvent, fTwo);

        function fTwo(e:Event):void
         {
             trace (a);
          }
   }

The general idea is really to pass a second parameter to the fTwo…

thanks!
/j

@ayumilove, thanks for your answer…

hmmm, I see now that my code was not as clear as i did see last night, with a lot of hours awake…

what I tried to say in the second example was if I can (or should, or shouldn’t) nest the function Two as a local function of function One – and so have access to f One’s local variable.

It is what I finally used, because in my simple example it was giving me the correct answers. But I really don’t know if in more complex situations the garbagecollector will destroy function One while function Two is still waiting for an event…
Do you know??

/br
/j

it should have looked like:

      function fOne() 
        {
            var a:int = 0;
            this.addEventListener(someEvent, fTwo);
            function fTwo(e:Event):void
              {
                    trace (a);
                 }
        }

hello, how would i simplify this i have a lot of mouse over and outs to do in this project
here is an example of two of them how would i simplify this code? maybe a conditional statement? im a little lost thanks

stop();
infoBox_mc.visible = false;
bergen_mc.addEventListener(MouseEvent.ROLL_OVER,b1);
bergen_mc.addEventListener(MouseEvent.ROLL_OUT,b2);
passiac_mc.addEventListener(MouseEvent.ROLL_OVER,p1);
passiac_mc.addEventListener(MouseEvent.ROLL_OUT,p2);
function b1(event:MouseEvent):void{
    infoBox_mc.info_txt.text = "Bergen County";
    infoBox_mc.visible = true;
    infoBox_mc.startDrag(true);}
function b2(event:MouseEvent):void{
    infoBox_mc.visible = false;}
function p1(event:MouseEvent):void{
    infoBox_mc.info_txt.text = "Passiac County";
    infoBox_mc.visible = true;
    infoBox_mc.startDrag(true);}
function p2(event:MouseEvent):void{
    infoBox_mc.visible = false;}

I think I have found the solution.

I moved the event listener from the container_mc to the my_thumb

my_thumb.contentLoaderInfo.removeEventListener(Eve nt.COMPLETE, thumbLoaded); 

Then I used this code in the call_Full

var Full_xml= my_project[e.target.name].@link;

Many thanks for your help!

Hello Michael Williams!
Thanks for your article, but I have 1 question on the same theme.
Can you explain why we use dispatchEvent sometimes?