ADOBE® FLEX® 3: BUILDING AND DEPLOYING ADOBE FLEX 3 APPLICATIONS

CHAPTER 4

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// Set expiration date to a date in the past.

response.setDateHeader("Expires", 946080000000L); //Approx Jan 1, 2000

// Force always modified.

response.header("Last-Modified", new Date());

Reducing SWF file sizes

You can improve initial user experience by reducing the time it takes to start an application. Part of this time is

determined by the download process, where the SWF file is returned from the server to the client. The smaller the

SWF file, the shorter the download wait. In addition, reducing the size of the SWF file also results in a shorter

application initialization time. Larger SWF files take longer to unpack in Flash Player.

The mxmlc compiler includes several options that can help reduce SWF file size.

Using the bytecode optimizer

The bytecode optimizer can reduce the size of the Flex application’s SWF file by using bytecode merging and

peephole optimization. Peephole optimization removes redundant instructions from the bytecode.

If you are using Flex Builder or the mxmlc command-line compiler, you can set the optimize compiler option to

true, as the following example shows:

mxmlc -optimize=true MyApp.mxml

The default value of the optimize option is true.

Disabling debugging

Disabling debugging can make your SWF files smaller. When debugging is enabled, the Flex compilers include

line numbers and other navigational information in the SWF file that are only used in a debugging environment.

Disabling debugging reduces functionality of the fdb command-line debugger and the debugger built into Flex

Builder.

To disable debugging, set the

debug compiler option to false. The default value for the mxmlc compiler is false.

The default value for the compc compiler is

true.

For more information about debugging, see “Using the Command-Line Debugger” on page 245.

Using strict mode

When you set the strict compiler option to true, the compiler verifies that definitions and package names in

import statements are used in the application. If the imported classes are not used, the compiler reports an error.

The following example shows some examples of when strict mode throws a compiler error:

package {

import flash.utils.Timer; // Error. This class is not used.

65ADOBE FLEX 3

Building and Deploying Adobe Flex 3 Applications

import flash.printing.* // Error. This class is not used.

import mx.controls.Button; // Error. This class is not used.

import mx.core.Application; // No error. This class is used.

public class Foo extends Application {

}

}

The strict option also performs compile-time type checking, which provides a small optimization increase in

the application at run time.

The default value of the

strict compiler option is true.

Examining linker dependencies

To find ways to reduce SWF file sizes, you can look at the list of ActionScript classes that are linked into your SWF

file.

You can generate a report of linker dependencies by setting the link-report compiler option to true. The output

of this compiler option is a report that shows linker dependencies in an XML format.

The following example shows the dependencies for the ProgrammaticSkin script as it appears in the linker report:

<script name="C:\flex3sdk\frameworks\libs\framework.swc(mx/skins/ProgrammaticSkin)"

mod="1141055632000" size="5807">

<def id="mx.skins:ProgrammaticSkin"/>

<pre id="mx.core:IFlexDisplayObject"/>

<pre id="mx.styles:IStyleable"/>

<pre id="mx.managers:ILayoutClient"/>

<pre id="flash.display:Shape"/>

<dep id="String"/>

<dep id="flash.geom:Matrix"/>

<dep id="mx.core:mx_internal"/>

<dep id="uint"/>

<dep id="mx.core:UIComponent"/>

<dep id="int"/>

<dep id="Math"/>

<dep id="Object"/>

<dep id="Array"/>

<dep id="mx.core:IStyleClient"/>

<dep id="Boolean"/>

<dep id="Number"/>

<dep id="flash.display:Graphics"/>

</script>