Question

I am new to ActionScript so excuse me if this is a stupid question.

So, I created a class, extended the sprite class, and now in the constructor I am trying to set the Sprite’s width and height properties which are inherited from the DisplayObject. However, after I set this.width and this.height, and print the values, I get 0 for both.

What the heck is going on? When I view the livedocs I see that DisplayObject has width and height listed as public properties. I have been able to instantiate a Sprite directly, and set the width and height after it’s been instantiated, so I don’t get it.

package  {
    import flash.display.*;

    public class ScrollBar extends Sprite {
        public function ScrollBar(width:Number, height:Number) {
            trace(width + "x" + height);
            this.width = width;
            this.height = height;
            trace(this.width + "x" + this.height);          
    }
}

Output:

20x400
0x0

Answer 1

From the docs:

The width is calculated based on the
bounds of the content of the display
object. When you set the width
property, the scaleX property is
adjusted accordingly … Except for
TextField and Video objects, a display
object with no content (such as an
empty sprite) has a width of 0, even
if you try to set width to a different
value.

You’ll need to render something as part of the sprite to get a valid w/h.