3.3 Using flex 3 in a flex 4 world  (Page 2/6)

Beginning in the Fall 2010 semester, I will upgrade my Introduction to XML course to include both Flex 3 and Flex 4.

Flex is a cryptic shorthand programming language

The important thing to remember is that Flex (versions 3 and 4) is simply cryptic xml-based shorthand programming languages that can be used tocreate some aspects ActionScript programs. You should also remember that anything that can be programmed in Flex can be programmed directly inActionScript. However, the reverse is not true.

When Adobe released Flex 4 and Flash Builder 4, they actually added a large number of classes to the ActionScript application programming interface (API) . So, the real question is not whether you should use Flex 4. The real question is whether the new classes that were added to the API are useful inyour application. If so, use them. If not, stick with the classes that were part of the API before the new classes were added.

Understanding Flex

If you really want to understand Flex (instead of simply using it in cookbook fashion) you need to learn about object-oriented programming using ActionScript.

Viewing tip

I recommend that you open another copy of this document in a separate browser window and use the following links to easily find and view the figures andlistings while you are reading about them.

Figures

• Figure 1 . Test program output for alpha values of 0.0, 0.33, 0.66, and 1.0.
• Figure 2 . The FlashDevelop IDE at startup.
• Figure 3 . The new project dialog.
• Figure 4 . The FlashDevelop IDE for a new project named test.
• Figure 5 . FlashDevelop text editor showing skeleton code for a Flex 3 project.
• Figure 6 . Test program output displayed in the Flash Player.
• Figure 7 . FlashDevelop showing the Debug/Release pull-down list.
• Figure 8 . The New Flex Project dialog in Flash Builder 4.
• Figure 9 . Contents of the project tree for the test program with Flash Builder 4.

Listings

• Listing 1 . Flex application named test.mxml.

Supplemental material

I recommend that you also study the other lessons in my extensive collection of online programming tutorials. You will find a consolidated index at www.DickBaldwin.com .

Preview

You learned how to create a Flex project named AppBackground01 using Flex Builder 3 in the earlier lesson titled The Default Application Container - Flex 3 and Flex 4 . However, Flex Builder 3 is no longer available from the Adobe website.

Therefore, in this lesson, I will explain how to create the same Flex project in three different ways. However, in this lesson, I will shorten the name of theproject by changing the project name to test .

Discussion and sample code

Run the program

Before continuing, I suggest that you run the program to familiarize yourself with the screen output.

Different ways to create Flex 3 applications

Here is a list of four different ways that you can create Flex 3 applications:

1. Use Flex Builder 3 if you already have it or can find it on the web.
2. Download and use the free open-source Adobe Flex 3 SDK (see Resources ).
3. Download and use the free FlashDevelop IDE ( see Resources )
4. Download and use Flash Player 4 with the Flex 3 SDK ( see Resources )