In each case you have to use the ExternalInterface. You call it from the flash application with parameters for the new height and width value of the flash container. On the other side you have to define an javascript function which do the resize operation with these values.

Here is an AS3 class which already includes the JavaScript part. Soyou don’t have to define an extra JS function. So you just have to import the AS3 class into your project and your ready to resize you application from Flash.

There are three methods to call:

• resize:This method takes two parameters height and width to completly set the absolute height and width of the flash application.
• addHeight: Takes one integer parameter. The value will be added to the current height. So “50″ for 50px more height or “-20″ for 20px less in height.
• addWidth: Takes one integer parameter. The value will be added to the current width. So “50″ for 50px more width or “-20″ for 20px less in width.

/**
 * resizes the flash container to needed dimensions
 * @param height - new needed height
 * @param width - new needed with
 */
public function resize( height:int, width:int ):void

/**
 * adds a specific value (+/-) to current height
 * @param valueHeight
 */
public function addHeight( valueHeight:int ):void

/**
 * adds a specific value (+/-) to current width
 * @param valueHeight
 */
public function addWidth( valueWidth:int ):void

To resize your application you could add an resize event handler to check specific containers for resize and do the resizing via this class in the event handler method. If you have fixed sizes per state you could of course also do it the static way.

/**
 * @author: Sebastian Martens; sebastian@sebastian-martens.de
 * @copyright: Creative Commons. Free to use "as is"
 *
 * Test Application
 */
package{
 
	import com.nonstatics.swfSelfResize.swfSelfResize;
 
	import flash.display.Sprite;
 
	[SWF(frameRate="31", width="500", height="100", backgroundColor="0x008866")]
	public class swfSelfResizeTest extends Sprite{
 
		private var resize:swfSelfResize;
 
		/**
		 * constructor
		 */
		public function swfSelfResizeTest(){
			super();
 
			this.resize = new swfSelfResize();
 
			// resize to 500px height, 400px width
			this.resize.resize( 500, 400 );
 
			// add 50px height -> 550px height
			this.resize.addHeight( 50 );
 
			// remove 10px width -> 390px
			this.resize.addWidth( -10 );
		}
 
	}
}

Download com.nonstatics.swfSelfResize.as (12kB)
Download bin-debug (20kB)
Full Flash Builder Project (131kB)

Be aware of the security model of the flash player! This won’t work on local filesystem (file://xyz). So please use it on your server (http://www.yourdomain.com) or with your locally installed testserver (http://localhost/whatever).

Hope this helps you.

cheers,
Sebastian