Flex ActionScript Project Error in Object Declaration.(project.mxml file)

Question

I have a Flex ActionScript Application, I need to draw a simple rectangle in stage. I am using firstapp.mxml and another Class called Book.as;

here is the complete code which i have done.

firstapp.mxml

<?xml version="1.0" encoding="utf-8"?>
<mx:Application 
    xmlns:mx="http://www.adobe.com/2006/mxml" 
    layout="absolute">

    <mx:Script>
        <![CDATA[
            import com.books.Book;
            import flash.display.*;

            var n:Book = new Book;
            //n.var1 = "Another String";
            addChild(n);
        ]]>
    </mx:Script>

</mx:Application>

Book.as

package com.books
{
    import flash.display.*;

    public class Book extends Sprite
    {
        public var var1:String = "Test Var";
        public var var2:Number = 1000;

        public function Book()
        {

            var b = new Sprite;
            b.graphics.beginFill(0xFF0000, 1);
            b.graphics.drawRect(0, 0, 500, 200);
            b.graphics.endFill();
            addChild(b);
        }

    }
}

I'm new in Flex, So please help me to fix this. I want to show the rectangle.

Marcus Stade · Accepted Answer · 2010-11-16 11:07:42Z

Since you're trying to add this to a flex component, you probably need to wrap Book in a UIComponent instance:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application 
    xmlns:mx="http://www.adobe.com/2006/mxml" 
    layout="absolute">

    <mx:Script>
        <![CDATA[
            import com.books.Book;
            import flash.display.*;

            var n:UIComponent = new UIComponent;
            n.addChild(new Book);
            addChild(n);
        ]]>
    </mx:Script>

</mx:Application>

Another way of doing this would be to instead make Book inherit UIComponent, like so:

package com.books
{
    import flash.display.*;

    public class Book extends UIComponent
    {
        public var var1:String = "Test Var";
        public var var2:Number = 1000;

        override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void
        {
            graphics.beginFill(0xff0000, 1);
            graphics.drawRect(0, 0, 500, 200);
            graphics.endfill();
        }
    }
}

Then you can add Book directly to your application, like so:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application 
    xmlns:mx="http://www.adobe.com/2006/mxml" 
    xmlns:books="com.books.*"
    layout="absolute">

    <books:Book />

</mx:Application>

Additionally, I suggest you read up on the Flex component architecture. There's some pretty good documentation from Adobe on the subject, but you should be aware that the information is specific to Flex 3 (I noticed you're using Flex 3, hence the link). Even while a lot of the information may still be applicable to Flex 4 (the component lifecycle for instance) there are differences, especially in terms of skinning.

Adrian Pirvulescu · Accepted Answer · 2010-11-16 11:17:01Z

1

USE var n:Book = new Book(); instead of var n:Book = new Book;

answered Nov 16, 2010 at 11:17

Adrian Pirvulescu

4,3403 gold badges32 silver badges47 bronze badges

4 Comments

Marcus Stade Over a year ago

Actually, it's valid ActionScript 3 syntax to omit the parenthesis.

Adrian Pirvulescu Over a year ago

@macke... Hmmm have you tested it ?

Marcus Stade Over a year ago

Yes, in fact I often use it to make code more readable. For instance, 'addChild(new Book)' reads better than 'addChild(new Book())'. I think that this only applies to constructors in conjunction with the 'new' keyword, however, not regular methods.

Adrian Pirvulescu Over a year ago

I think you may have problems with this, if it works then you're lucky but this is not the "normal" way of calling a constructor. What happens if the constructor needs params ;)

alxx · Accepted Answer · 2010-11-18 06:47:51Z

0

macke showed you good way. But if you want just to show something quickly, change

addChild(b);

to

rawChildren.addChild(b);

Edit: Some clarifications: application is UIComponent, therefore its addChild method needs UIComponent. You want to add Sprite. This can be done with rawChildren.addChild method from application. rawChildren is useful to get Sprites work with UIComponents, but you have to manage sprites yourself (sizes and layout).

edited Nov 18, 2010 at 6:47

answered Nov 16, 2010 at 11:40

alxx

9,8974 gold badges28 silver badges41 bronze badges

1 Comment

Marcus Stade Over a year ago

It's probably useful to know what the difference between the two are, especially since rawChildren is an API that is anything but deprecated in Flex 4. This url might prove useful: billdwhite.com/wordpress/?p=296

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