R – Flex: Binding to an MXML-esque “binding string” in action script

Flex suppresses errors inside of data setters, because stuff is frequently null. The problem is probably that your subcomponent is not initialized when set data is called. If you really can't use binding (the easy and clean way), then you should delay setting the data of the subcomponent until it is initialized with invalidateProperties / commitProperties.

In the data setter, call invalidateProperties() and set a flag saying they've changed.

Override commitProperties (don't forget to call super), check the flag, and if it's true, set the subcomponent's data.

If your commitProperties block never gets called, try invalidateProperties on creationComplete.

Here is a function I coded long time ago. It takes a DisplayObject(mxml components are DisplayObject too), it will return a Bitmap of it.

You may write a handler to listen for Event.RENDER of the mxml component to update the Bitmap when the component is changed.

Another thing you can try on the FlexBook component is to set creationPolicy="all"...

/**
 * This function returns a Bitmap that have the same look of a given DisplayObject.
 * Ref.: http://qops.blogspot.com/2008/05/bitmap.html
 * @author Andy Li andy@onthewings.net
 * @version 20080529
 */
package net.onthewings{
    import flash.geom.Point;
    import flash.geom.Rectangle;
    import flash.geom.Matrix;
    import flash.display.DisplayObject;
    import flash.display.Bitmap;
    import flash.display.BitmapData;
    import flash.display.PixelSnapping;
    import flash.display.Stage;

    public function bitmapEquivalentOf(obj:DisplayObject, extendsRectSidesBy:Number = 0, clipOutside = null,alpha:Boolean = true):Bitmap {
        if (obj.width && obj.height) {
            var bitmapData:BitmapData = new BitmapData(obj.width, obj.height, alpha, 0xFFFFFF);
            var rect:Rectangle = obj.getBounds(obj);
            var matrix:Matrix = new Matrix;
            matrix.translate(-rect.x, -rect.y);
            bitmapData.draw(obj, matrix);
            var bitmap:Bitmap = new Bitmap(bitmapData, PixelSnapping.AUTO, true);
            bitmap.x = rect.x;
            bitmap.y = rect.y;
            var ebd:BitmapData;

            if (clipOutside) {
                var h:Number;
                var w:Number;
                if (clipOutside is Stage) {
                    h = clipOutside.stageHeight;
                    w = clipOutside.stageWidth;
                } else {
                    h = clipOutside.height;
                    w = clipOutside.width;
                }
                if(!(h && w)){
                    return null;
                }
                var pt:Point = obj.localToGlobal(new Point(rect.x,rect.y));
                ebd = new BitmapData(w, h, true, 0xFFFFFF);
                ebd.copyPixels(bitmap.bitmapData,new Rectangle(-pt.x,-pt.y,w,h),new Point(0,0));
                bitmap =  new Bitmap(ebd, PixelSnapping.AUTO, true);
            } else if (extendsRectSidesBy) {
                ebd = new BitmapData(bitmapData.width+extendsRectSidesBy*2, bitmapData.height+extendsRectSidesBy*2, true, 0xFFFFFF);
                ebd.copyPixels(bitmap.bitmapData,bitmap.bitmapData.rect,new Point(extendsRectSidesBy,extendsRectSidesBy));
                bitmap =  new Bitmap(ebd, PixelSnapping.AUTO, true);
                bitmap.x = rect.x - extendsRectSidesBy;
                bitmap.y = rect.y - extendsRectSidesBy;
            }
            return bitmap;
        } else {
            return null;
        }
    }
}