Flex Examples

6 Responses to “Creating a component instance by class name in ActionScript 3.0”

1. 1 andrew Sep 3rd, 2008 at 9:54 am

   Thanks for the code. Works perfect.

   Let’s say you created 10 components. And then you want to reference those components in actionscript. How would you do so?

   For example, let’s say you wanted to dynamically change the background of one of the components. How you you write the actionscript (instance.backgrouColor = #000000 ??? )

   Andrew.

2. 2 peterd Sep 3rd, 2008 at 10:32 am

   andrew,

   You could use getChildAt() or getChildByName() to access the dynamically created component instances. Something like the following:

   <?xml version="1.0" encoding="utf-8"?>
   <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
           layout="vertical"
           verticalAlign="middle"
           backgroundColor="white"
           creationComplete="init();">
   
       <mx:Script>
           <![CDATA[
               import flash.utils.getDefinitionByName;
               import mx.controls.Button;
   
               private const dummyArr:Array = [Button];
   
               private function init():void {
                   var c:Class = getDefinitionByName("mx.controls.Button") as Class;
                   var idx:uint;
                   var len:uint = 5;
                   for (idx = 0; idx < len; idx++) {
                       var obj:Button = new c();
                       obj.label = "Button " + idx;
                       obj.name = "button" + idx;
                       addChild(obj);
                   }
               }
   
               private function btn_click(evt:MouseEvent):void {
                   var b:Button = getChildByName("button3") as Button;
                   b.label = "OUCH";
               }
           ]]>
       </mx:Script>
   
       <mx:ApplicationControlBar dock="true">
           <mx:Button id="btn"
                   label="Change Button 3"
                   click="btn_click(event);" />
       </mx:ApplicationControlBar>
   
   </mx:Application>
   

   Peter

3. 3 andrew Sep 3rd, 2008 at 11:42 am

   Thank you so much Peter - that makes a lot of sense.However, for some reason, my code is throwing an error: “Cannot accesss the property of a null object…”

   This is my code in a nutshell:

   The following code is in a loop where “contentType” changes between Text, TextArea and Image. It outputs perfectly (thanks to you!).

   var c:Class = getDefinitionByName('mx.controls.'+contentType) as Class;
   var obj:UIComponent = new c();
   
   if (obj) {
   switch (obj.className) {
       case "Text":
           Text(obj).id = contentID;
           Text(obj).text = content;
           Text(obj).x = contentxPos;
           Text(obj).y = contentyPos;
           Text(obj).width = contentWidth;
           Text(obj).height = contentHeight;
           Text(obj).styleName = contentStyleName;
           break;
       case "TextArea":
           TextArea(obj).id = contentID;
           TextArea(obj).text = content;
           TextArea(obj).x = contentxPos;
           TextArea(obj).y = contentyPos;
           TextArea(obj).width = contentWidth;
           TextArea(obj).height = contentHeight;
           TextArea(obj).styleName = contentStyleName;
           break;
       case "Image":
           Image(obj).name = "54237";
           Image(obj).id = contentID;
           Image(obj).source = contentSource;
           Image(obj).x = contentxPos;
           Image(obj).y = contentyPos;
           Image(obj).width = contentWidth;
           Image(obj).height = contentHeight;
           Image(obj).setStyle('completeEffect', slowFade);
           Image(obj).addEventListener(MouseEvent.CLICK, showImageGallery);
           Image(obj).addEventListener(FlexEvent.CREATION_COMPLETE, creationCompleteHandler);
           break;
   }
   main.addChild(obj);
   }
   

   …but then I use:

   var i:Image = getChildByName("54237") as Image;
   i.source = '/myimage.jpg';
   

   And it doesn’t work. Note that I just hardcoded “54237″ for testing…

   Any suggestions ???

   Thanks again!

4. 4 andrew Sep 3rd, 2008 at 11:47 am

   …note that the second line should read:
   var obj:UIComponent = new c();

5. 5 peterd Sep 3rd, 2008 at 12:44 pm

   andrew,

   Try using main.getChildByName() instead:

   var i:Image = main.getChildByName("54237") as Image;
   

   Peter

6. 6 andrew Sep 3rd, 2008 at 1:05 pm

   Yes! That was it.

   It took me about 5 hours to figure this one out.

   You rock!

   Andrew.

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