Setting width/height too early??

Question

I noticed if I set width and/or height before adding it to
displayList, the displayObject simply won't show up. The following
code is a cut&paste from livedoc (SimpleButton), except that I
add a line of "button.width=20".
If, however, I move the line to after addChild(), things work
normally.
Why?:confused: :confused: :confused:
[CODE]
package {
import flash.display.*;
import flash.events.*;
public class SimpleButtonDemo extends Sprite {
public function SimpleButtonDemo( ) {
// Create a simple button and configure its location
var button:SimpleButton = new SimpleButton( );
button.x = 20;
button.y = 20;
//// ################# Added by me. Button won't show up any
more.
button.width = 80;
// Create the different states of the button, using the
// helper method to create different colors circles
button.upState = createCircle( 0x00FF00, 15 );
button.overState = createCircle( 0xFFFFFF, 16 );
button.downState = createCircle( 0xCCCCCC, 15 );
button.hitTestState = button.upState;
// Add an event listener for the click event to be notified
// when the user clicks the mouse on the button
button.addEventListener( MouseEvent.CLICK, handleClick );
// Finally, add the button to the display list
addChild( button );
//// ############### This works, if added here!!!!
// button.width = 20;
// Helper function to create a circle shape with a given
color
// and radius
private function createCircle( color:uint, radius:Number
):Shape {
var circle:Shape = new Shape( );
circle.graphics.lineStyle( 1, 0x000000 );
circle.graphics.beginFill( color );
circle.graphics.drawCircle( 0, 0, radius );
circle.graphics.endFill( );
return circle;
// Event handler invoked whenever the user presses the
button
private function handleClick( event:MouseEvent ):void {
trace( "Mouse clicked on the button" );
}[/CODE]

Answer 1

You're using the simple button class. Just because you
instantiate an object of this class doesn't mean you've added
anything to the button.
What I'm trying to tell you is that addChild has nothing to
do with it. Simple Button just happens to be dependent on what is
defined inside the button states themselves.
For instance, comment out your hitStates leaving your width
call after the addChild and you should notice the same behavior as
before. By defining the button states, you are actually adding
content to the container that will be drawn to the display when
addChild is called.
You can define your height and width anytime after you have
defined the states for the button. At this point, Flash will then
have content to manipulate. Until you have drawable content to push
to the display list, nothing will happen when width and height are
called.