An AS component doesn't appear in a flex app

Question

The following AS draws a line and works in its own right,
package components {
import flash.display.Sprite;
import flash.display.Shape;
public class DrawTest1 extends Sprite {
public function DrawTest1() {
var shape:Shape = new Shape();
shape.graphics.lineStyle(0,0x0000FF, 1);
shape.graphics.lineTo(100,100);
addChild(shape);
It was then included in a flex app as
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
xmlns:custom="components.*"
layout="horizontal">
<custom:DrawTest1 />
</mx:Application>
but only a blank screen (i.e. without the line) was displayed
when the flex app was executed (no error message was given during
compilation). Please help.

Answer 1

Flex containers (incluing Application) can contain only
components which are derived from UIComponent or implement
IUIComponent interface.
To get your component to display in the application create a
UIComponent as child and add the DrawTest1 component as a child to
it.
<mx:UIComponent id="p1"
creationComplete="p1.addChild(t1)"/>
<custom:DrawTest1 id="t1"/>