Very simple really, google does most of the heavy lifting. Simply load this url as you would to load an external image:
http://chart.apis.google.com/chart?cht=qr&chl=[YOUR-URL]&chs=120×120
Replacing the [YOUR-URL] with a url, i.e. http://bbc.co.uk – and the 120×120 with your own width and height
Example:
var myLoader:Loader = new Loader();
myLoader.load(new URLRequest(“http://chart.apis.google.com/chart?cht=qr&chl=http://bbc.co.uk&chs=150×150”));
Would dynamically load a QR code for bbc.co.uk, with dimensions 150 by 150, and load it into the Loader instance myLoader, and would look like this