TechNote

Using ExternalInterface within a <form> tag causes communication between JavaScript and ActionScript to fail

Issue

Communication between JavaScript and ActionScript fails if a Flash or Flex movie uses ExternalInterface inside a form tag in Internet Explorer. The following error is displayed when you load, refresh, or close the page, or when you close the browser:

Error: [flash_movie_id] is undefined.

This issue also occurs with the Flex AJAX Bridge (FABridge), which uses the ExternalInterface. A .swf file placed inside a <form> tag will not be accessible through FABridge functions and will fail to load due to the initialization functions that are called automatically.

The following code sample uses ExternalInterface within a form tag and will return the above error message:

 <form>
		

	      <script type="text/javascript">
		

	      AC_FL_RunContent( 'codebase','http://fpdownload.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=8,0,0,0','width','796','height','200','id','sample','align','middle','src','externalinterface','allowscriptaccess','always','quality','high','bgcolor','#ffffff','name','sample','pluginspage','http://www.macromedia.com/go/getflashplayer','movie','externalinterface' ); //end AC code
		

	      </script>
		

	 
		

	      <noscript><object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0"  >
		

	      <param name="movie" value="externalinterface.swf" />
		

	      <param name="quality" value="high" />
		

	      <embed href="externalinterface.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash"  ></embed>
		

	      </object></noscript>
		

	      </form>

Solution

Solution 1: Use JavaScript to create the required reference to your Flash movie in the window object.

Add the following script after the embedded Flash movie:

window.[flash_movie_id] = document.forms[0].[flash_movie_id] ;

For example, if your flash_movie_id is called "sample" you would use the following:

<script type="text/javascript">window.sample = document.forms[0].sample;</script>

Solution 2: Add a nested form tag after the first form tag in the page.

For the sample code above, add <form></form> after the existing form tag, like this:

 <form><form></form>
		

	   <script type="text/javascript">
		

	   AC_FL_RunContent( 'codebase','http://fpdownload.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=8,0,0,0','width','796','height','200','id','sample','align','middle','src','externalinterface','allowscriptaccess','always','quality','high','bgcolor','#ffffff','name','sample','pluginspage','http://www.macromedia.com/go/getflashplayer','movie','externalinterface' ); //end AC code
		

	   </script>
		

	 
		

	   <noscript><object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=7,0,19,0"  >
		

	   <param name="movie" value="externalinterface.swf" />
		

	   <param name="quality" value="high" />
		

	   <embed href="externalinterface.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash"  ></embed>
		

	   </object></noscript>
		

	   </form>