Apache – Flex: Where do ChildConstraintInfo objects come from

Don't forget that since Flex is open source you can track this sort of thing down in the code.

I found a function called NameUtil.displayObjectToString that seems to be responsible for creating the printable name of a Flex instance. There is also NameUtil.createUniqueName which creates the name property.

Have a look at the code, but basically createUniqueName splits getQualifiedClassName to get just the class name without the package details. NameUtil has a static counter that it then appends to the end of that name. so Button15 is the 15th FlexSprite created by your application.

displayObjectToString isn't too more complicated, except it follows the chain of components through the parents joining the names on a "."

One thing to note is a comment in UIComponent.as:

/**
 *  ID of the component. This value becomes the instance name of the object
 *  and should not contain any white space or special characters. Each component
 *  throughout an application should have a unique id.
 *
 *  <p>If your application is going to be tested by third party tools, give each component
 *  a meaningful id. Testing tools use ids to represent the control in their scripts and
 *  having a meaningful name can make scripts more readable. For example, set the
 *  value of a button to submit_button rather than b1 or button1.</p>
 */
public function get id():String
{
    return _id;
}

It says: "This value becomes the instance name of the object" and although that appears to be true I cannot find out where the assignment from id to name happens. It could be in the AS3 code that is generated from the MXML when it is converted during compilation.

I found that using a grid control works very nicely to accomplish the task, and without adding in blank labels:

<mx:Grid width="100%" height="100%">
  <mx:GridRow height="20%"/>
  <mx:GridRow height="60%">
    <mx:GridItem verticalAlign="middle" horizontalAlign="center">
      <mx:Label text="Label A" fontSize="60" fontFamily="Arial"/>   
    </mx:GridItem>
  </mx:GridRow>
  <mx:GridRow height="20%" verticalAlign="middle">
    <mx:GridItem verticalAlign="middle" horizontalAlign="center">
      <mx:Label text="Label B" fontSize="24" fontFamily="Arial"/>
    </mx:GridItem>
  </mx:GridRow>         
</mx:Grid>