Question

Consider the following radio button example.

<?xml version='1.0' encoding='utf-8'?> <mx:Application xmlns:mx='http://www.adobe.com/2006/mxml'> <mx:Script> <![CDATA[     private function getRb1():RadioButton {         trace(rb1 == null);         return rb1;                          }    ]]>  </mx:Script> <mx:VBox>     <mx:RadioButtonGroup **id='rbg' selection='{getRb1()}**'/>           <mx:RadioButton id='rb1' label='Radio Button 1' />     <mx:RadioButton id='rb2' label='Radio Button 2' />     <mx:RadioButton id='rb3' label='Radio Button 3' /> </mx:VBox>    </mx:Application> 

The problem is that I can not refer to rb1 while defining RadioButtonGroup, rb1 is null at that time, but i can use the selectedValue to set the initial selction.

I was just wondering is this some special case or its not safe to refer to components in mxml in general.

Thanks,

Answer 1

I’m not quite sure what you’re asking, but hopefully this’ll answer your question — from the Flex docs:

RadioButtonGroup.selection
Contains a reference to the currently selected RadioButton control in the group. You can access the property in ActionScript only; it is not settable in MXML. Setting this property to null deselects the currently selected RadioButton control.

In general, though, making component references in MXML is totally fine; that’s how effects are often handled, among many other things. For example:

<mx:Glow id='g' /> <mx:Label showEffect='{g}' /> 

However in your case, assuming you’re having trouble setting the selected item, it might be because you haven’t specified the group attribute on the radio buttons; omitting that detaches the group component from the individual buttons. Once you add that, you can bind the group’s selection property using a Bindable variable containing a reference to a component, like so:

<mx:Script>     <![CDATA[          [Bindable]         private var selectedRadioButton:RadioButton;              private function this_creationComplete(event:Event):void         {             selectedRadioButton = rb1;         }          private function btn_click(event:Event):void         {             selectedRadioButton = rb2;         }      ]]>  </mx:Script> <mx:VBox>     <mx:RadioButtonGroup id='rbg' selection='{selectedRadioButton}' />     <mx:RadioButton id='rb1' group='{rbg}' label='Radio Button 1' />     <mx:RadioButton id='rb2' group='{rbg}' label='Radio Button 2' />     <mx:RadioButton id='rb3' group='{rbg}' label='Radio Button 3' />      <mx:Button label='Choose a Different Button' click='btn_click(event)' /> </mx:VBox>  

Does this make sense? Hopefully it’s not completely off the mark; post back and let me know and I’ll try to help out as best I can.