One of the great things about Flex is that you get to spend most of your time working on the business logic and workflow, and less on the cosmetic aspect. This is because the Flex default's look-and-feel is great! The only problem of course is that most people won't spend much time customizing the look, resulting in many Flex apps looking the same. In Flex 1.5 many folks customized the color scheme, but few ventured into modifying the actual skins of the components.

 The designer approach would be to modify the graphical aspects of a theme, a laborious process of editing many items in various Flash source files ("FLAs") using the Flash Professional IDE.

The second approach let advanced Flex programmers create extremely customized interfaces; however this approach made it difficult for designers and developers to hand off the graphical "assets" of a project.

In Flex 2 things got a whole lot easier. In this article we'll look at the basics of changing the look-and-feel of your Flex application by introducing Flex Themes, Styles, and Skins.

Terminology
Before we get into it, let's quickly define what all the terms means.

Themes are simply a collection of style definitions, images (a k a graphical assets), and skins. Themes give you a lot of control and convenience in terms of how you package it all together and distribute it. You can distribute your theme as separate individual files, or ideally compile it into a theme SWC (commonly pronounced as "swick," a sort of JAR/ZIP-like archive format for Flash).

Styles are similar to the CSS you've been using for your Web applications. In fact, Flex's styles follow the CSS 2.0 syntax and support many of the common style properties that you're used to.

Although many of the visual components and controls support a variety of style properties that let you control fine-grain details like the corner radius of a button, fill gradients, and transparency. They're still based on a certain look; using skins you can completely alter the graphics and interface behavior.

Out of the Box
Out-of-the-box there are a couple of things you can do to easily change the look of your app. By default the Theme Flex uses is called Halo and it supports a style property called themeColor.

In HTML you can assign predefined colors like Red and Blue to certain CSS properties. Flex supports the same thing, but includes four interesting colors ready-to-use. They include:

• haloBlue (the default)
• haloOrange
• haloGreen
• haloSilver

<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" themeColor="haloOrange">

You can also do this on a per-component instance basis as well. For example:

<mx:Button label="My Button" themeColor="haloGreen">

Now don't get too excited. The difference is rather subtle in that the most noticeable change is when you mouse over various components. In the case of the button it changes the outer highlight, and with the Datagrid (see the graphic below) it changes the Header column.

Imaga A

Fortunately there's a much more dramatic change that you can employ with the out-of-the-box themes. The themes that come with Flex 2 are:

• Halo (the default, embedded in the framework.swc)
• HaloClassic (haloclassic.swc)
• Ice (Ice.css)
• Institutional (Institutional.css)
• Wooden (Wooden.css)
• Smoke (Smoke.css)

• Start off with a Project in Flex Builder 2 either by opening an existing one or creating a new one.
• Using the mouse, right-click on the project folder, and select properties

  Image B

• Select the Flex Compiler section
• Under "Additional compiler arguments," append the -theme parameter located as the desired theme file. For example:

  -theme "C:\Program Files\Adobe\Flex Builder 2\Flex SDK 2\frameworks\themes\Smoke.css"

• Now build and run the application