Question

I have this App.mxml:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" 
               xmlns:s="library://ns.adobe.com/flex/spark" 
               xmlns:mx="library://ns.adobe.com/flex/mx">
    <s:Button id="bt" label="click me"/>
</s:Application>

And this test case:

package flexUnitTests
{
    import flexunit.framework.Assert;

    public class AppTest
    {       
        [Test]
        public function testApp():void
        {
            var app:App = new App();
            Assert.assertNotNull(app.bt);
        }
    }
}   

But app.bt is null. I want to access the button 🙁

Answer 1

Short Answer:

The life cycle methods have not run on app; so no createChildren() method was executed in order to create the child component of bt.

Longer Answer:

Things get slightly more complicated with the main application file, as it there is no higher level Flex component in the display hierarchy. I’m unclear on all specifics, but..

I think the Flex Compiler does some magic to set up this component–and the Flex Framework–that help makes the whole app work. You are, in essence, bypassing that work by creating your own instance of the component.