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Flex 4: Event Listener created, but not being called?

Posted on 2010-09-13
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Last Modified: 2013-11-11
I'm trying to call an event I've created in another component. I've added trace() into my methods so I can see what's being called. Everything except for the event listener (myEvent) is being called. Can anyone tell me why this is please?

Any help and examples would be greatly appreciated. Thanks in advance.
// TestApp.mxml (application)
    <?xml version="1.0" encoding="utf-8"?>
    <s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009" 
                           xmlns:s="library://ns.adobe.com/flex/spark" 
                           xmlns:mx="library://ns.adobe.com/flex/mx"
                           xmlns:com="com.*"
                           creationComplete="initApp()">
        <fx:Script>
            <![CDATA[
                import com.MyPopUp;
                
                import mx.managers.PopUpManager;
                protected function initApp():void
                {
                    var popUp:MyPopUp = new MyPopUp();    
                    
                    PopUpManager.addPopUp(popUp, this);
                }    
            ]]>
        </fx:Script>
        <com:MyComp/>
    </s:WindowedApplication>
    
    // MyComp.mxml (component)
    <?xml version="1.0" encoding="utf-8"?>
    <s:VGroup xmlns:fx="http://ns.adobe.com/mxml/2009" 
              xmlns:s="library://ns.adobe.com/flex/spark" 
              xmlns:mx="library://ns.adobe.com/flex/mx"
              width="100%" height="100%"
              creationComplete="initComp()">
        <fx:Script>
            <![CDATA[
                import mx.controls.Alert;
                import mx.events.DynamicEvent;
                
                protected function initComp():void
                {
                    trace('init MyComp()');
                    
                    this.addEventListener('myEvent', myEvent);
                }
                
                private function myEvent(event:DynamicEvent):void
                {
                    trace('myEvent()');
                    
                    Alert.show('Event Called!', 'Success');
                }
            ]]>
        </fx:Script>
    </s:VGroup>
    
    // MyPopUp.mxml (component)
    <?xml version="1.0" encoding="utf-8"?>
    <s:Group xmlns:fx="http://ns.adobe.com/mxml/2009" 
             xmlns:s="library://ns.adobe.com/flex/spark" 
             xmlns:mx="library://ns.adobe.com/flex/mx" width="100" height="100">
        <fx:Script>
            <![CDATA[
                import mx.events.DynamicEvent;
                import mx.managers.PopUpManager;
                
                private function call(event:MouseEvent):void
                {
                    trace('call()');
                    
                    PopUpManager.removePopUp(this);
                    
                    var evt:DynamicEvent = new DynamicEvent('myEvent');
                    evt.value1 = '1234';
                    
                    dispatchEvent(evt);
                }
            ]]>
        </fx:Script>
        <s:Button click="call(event)" label="Call Event"/>
    </s:Group>

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Question by:DReade83
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7 Comments
 
LVL 20

Accepted Solution

by:
ChristoferDutz earned 500 total points
ID: 33665978
Hi,

glad you picked up my suggestion regarding the Events. Let me explain what's going on:
As soon as the main component is initialized, the popup is opened and the popup is a direct child of the main application.
Parallel to the Dialog the main application has another child, your component.

In your dialog you now fire an event in your dialog. So flex checks if the dialog itself has any listeners. Unfortunately not. This is why your component will never get the event.

What you would need, is to catch the event in the main application and to throw it at the component model directly.

For further reading I would suggest having a look at the event processing phases (Targeting Phase, Bubbling Phase, ...) to get a better understanding at how flex handles this.

Hope my modified code works for you.
// TestApp.mxml (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"
					   xmlns:com="com.*"
					   creationComplete="initApp()">
	<fx:Script>
		<![CDATA[
			import com.MyPopUp;
			
			import mx.controls.Alert;
			import mx.events.DynamicEvent;
			import mx.managers.PopUpManager;
			
			protected function initApp():void
			{
				var popUp:MyPopUp = new MyPopUp();
				popUp.addEventListener("myEvent", myEventListenerDirect);
				PopUpManager.addPopUp(popUp, this);
			}
			
			protected function myEventListenerDirect(event:DynamicEvent):void {
				myComp.dispatchEvent(event);
			}
		]]>
	</fx:Script>
	<com:MyComp id="myComp"/>
</s:Application>


    // MyComp.mxml (component)

<?xml version="1.0" encoding="utf-8"?>
<s:VGroup xmlns:fx="http://ns.adobe.com/mxml/2009" 
		  xmlns:s="library://ns.adobe.com/flex/spark" 
		  xmlns:mx="library://ns.adobe.com/flex/mx"
		  width="100%" height="100%"
		  creationComplete="initComp()">
	<fx:Script>
		<![CDATA[
			import mx.controls.Alert;
			import mx.events.DynamicEvent;
			
			protected function initComp():void
			{
				trace('init MyComp()');
				
				this.addEventListener('myEvent', myEvent);
			}
			
			private function myEvent(event:DynamicEvent):void
			{
				trace('myEvent()');
				
				Alert.show('Event Called!', 'Success');
			}
		]]>
	</fx:Script>
</s:VGroup>


    // MyPopUp.mxml (component)

<?xml version="1.0" encoding="utf-8"?>
<s:Group xmlns:fx="http://ns.adobe.com/mxml/2009" 
		 xmlns:s="library://ns.adobe.com/flex/spark" 
		 xmlns:mx="library://ns.adobe.com/flex/mx" width="100" height="100">
	
	<fx:Metadata>
		[Event(name="myEvent", type="mx.events.DynamicEvent")]
	</fx:Metadata>
	
	<fx:Script>
		<![CDATA[
			import mx.controls.Alert;
			import mx.events.DynamicEvent;
			import mx.managers.PopUpManager;
			
			private function call(event:MouseEvent):void
			{
				Alert.show('call()');

				var nonBubblingEvt:DynamicEvent = new DynamicEvent("myEvent");
				nonBubblingEvt.value1 = "1234";
				dispatchEvent(nonBubblingEvt);

				PopUpManager.removePopUp(this);
			}
		]]>
	</fx:Script>
	
	<s:Button click="call(event)" label="Call Event"/>
</s:Group>

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Author Comment

by:DReade83
ID: 33670243
Thanks very much.

On another site, someone suggested using Spring Framework and the EventBus to accomplish this. I've given it a go and it does indeed work.

Would you say this is a global event handler/listener? Do you think there would be any problems using this method?
0
 
LVL 20

Expert Comment

by:ChristoferDutz
ID: 33670448
Whooow ... Well you could certainly do this, but this would be as if you Flew your grandma to the supermarket using a brand-new Airbus A380 ;-) ... and it's certainly not faster.

You are trying to do a very simple task - I would suggest you stick to the simple solution. But if it works ... I just thought you wanted to learn Flex and I would suggest you dig into the flex event systen or you will have a really hard time understanding how you have to build your applications.
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Author Comment

by:DReade83
ID: 33670464
Yeah I totally understand what you mean. I'd like to avoid using frameworks if I can, as I've done in the past with PHP. I'll look into it some more. Thanks for your help though, much appreciated. :-)
0
 
LVL 20

Expert Comment

by:ChristoferDutz
ID: 33672444
So how about closing this question? I like to have my "open question" list nice and clean ;-)
0
 

Author Comment

by:DReade83
ID: 33672740
Oops... There you go. :-)
0
 
LVL 20

Expert Comment

by:ChristoferDutz
ID: 33672797
Thanks ;-)
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