Once you have downloaded the latest SDK in a ZIP format, extract it at your desired location, for example, C:\Flex3.1_SDK. That's it; you are done with the Flex SDK's installation. Now before you jump into coding, let's first understand the Flex SDK's installation directory structure.

When you install Flex SDK, the installer creates the following directory structure under the installation directory:

In order to compile your Flex application, you need to set your bin folder in the Windows PATH environment variable under your System settings, so that you can use mxmlc and compc compilers from your project root folder.

There are a couple of important configuration files that you need to be aware of before you start using SDK. They are as follows.

The flex-config.xml file defines the default compiler options for the compc and mxmlc command-line compilers. You can set and tweak many compiler- and application-related configuration parameters in the flex-config.xml file located under the sdk_install_directory/frameworks/ folder such as namespaces, library path, accessibility, and locale for application internationalization.

All of the Flex component names are defined in the mxml-manifest.xml file. This manifest file maps Flex component namespaces to class names with complete package names. This is similar concept as XML namespaces. The mxml-manifest.xml file is used to avoid element name conflicts and it also helps in organizing your source files. Don't worry about these files right now. You will learn more about them and their usage in a better manner further in the book.

Example:

<?xml version="1.0"?>
<componentPackage>
<component id="HelloLabel" class="usa.hello.HelloLabel"/>
<component id="NamasteLabel" class="ind.namaste.NamasteLabel"/>
</componentPackage>

In a manifest file, the id property of each<component> tag must be unique. That id is the name you use for the tag in your Flex applications, for example:

<local:HelloLabel label="Hello!"/>

You will learn more about how to use namespaces in Chapter 2 of this book.

The Flex compiler requires Java Runtime Environment (JRE) to compile Flex source code; configuring Java Virtual Machine (JVM) parameters can actually result in much faster and optimized compilation in some cases. Without JRE you cannot use Flex compilers, such as mxmlc and compc.

You can configure JVM settings in the jvm.config file, which is typically located under the sdk_install_dir/bin folder. The most common JVM configuration you may ever need is the JVM heap size. The Java heap is the amount of memory reserved for a particular JVM instance for faster performance; for example:

java.args=-Xms256m -Xmx512m