A common task that has changed drastically in ActionScript 3.0 is loading a library image via its linkageID into a BitmapData object and attaching it to a movieclip. In ActionScript 2.0, this can be done like so:

import flash.display.BitmapData
var bmp:BitmapData = BitmapData.loadBitmap("linkageID");
var img = createEmptyMovieClip("img",0);
img.attachBitmap(bmp,0);

In ActionScript 3.0 movieclips and bitmaps are not attached or created like this – everything is created with the new keyword. Also, a BitmapData object should be dropped into a new Bitmap, which can be added to the stage with the all-important addChild() method.

Since a library bitmap inherits from BitmapData, you now set the class of the bitmap its Linkage Properties in Flash CS3, instantiate it and wrap it in a Bitmap object that you add to the stage:

Where ‘Butterfly’ refers to the bitmap library item you’ve given the class definition ‘Butterfly’. The Base class is generated automatically. These five lines of code can be shortened to one, but is less readable:

var img = addChild(new Bitmap(new Butterfly(0,0)));

Note that in Flex Builder, unlike Flash CS3, you would embed an image using the embed meta tag, associating it with a variable, instead of its Linkage Properties dialog:

[Embed(source='image.jpg')] public var Butterfly:Class;

Building SWFs in Flex Builder is a whole different topic – so stay tuned!