沙漠中的魚

The syntax that you use for embedding assets depends on where in your application you embed the asset. Flex supports the following syntaxes:

• [Embed(parameter1, paramater2, ...)] metadata tag

  You use this syntax to embed an asset in an ActionScript file, or in an <mx:Script> block in an MXML file. For more information, see Using the [Embed] metadata tag.

• @Embed(parameter1, paramater2, ...) directive

  You use this syntax in an MXML tag definition to embed an asset. For more information, see Using the @Embed() directive in MXML.

• Embed(parameter1, paramater2, ...) directive

  You use this syntax in an <mx:Style> block in an MXML file to embed an asset. For more information, see Embedding assets in style sheets.

All three varieties of the embed syntax let you access the same assets; the only difference is where you use them in your application.

Escaping the @ character

You can use the slash character (\) to escape the at sign character (@) when you want to use a literal @ character. For example, the string "\@Embed(foo)" means the literal string "@Embed(foo)"). You use two slash characters (\\) to escape a single backslash character. For example, use the character string "\\@" to specify the literal strings "\@".

Embed parameters

Each form of the embed syntax takes one or more optional parameters. The exact syntax that you use to embed assets depends on where they are embedded. Some of these parameters are available regardless of what type of asset you are embedding, and others are specific to a particular type of media. For example, you can use the source and mimeType parameters with any type of media, but the scaleGridRight parameter applies only to images.

The following table describes the parameters that are available for any type of embedded asset. For more information, see About the source parameter and About the MIME type.

The following table describes the parameters that are specific for images and Sprite objects. For more information, see Using 9-slice scaling with embedded images.

The following table describes the parameter that is specific to SWF files. For more information, see Embedding SWF files.

About the source parameter

In almost all cases, you must specify the source parameter, or nothing is embedded.

The source parameter is the default parameter of the [Embed] metadata tag; therefore, if you are not specifying any other parameters, you can just supply its value without explicitly including the parameter name or assigning it the desired value, as the following example shows:

<mx:Style>    
    .myCustomButton {
        overSkin:Embed("overIconImage.gif");
        upSkin:Embed(source="upIconImage.gif");
        downSkin:Embed(source="downIconImage.gif");
    }
</mx:Style>

About setting the path to the embedded asset

You can specify a fully qualified path to the image or a URL, as the following examples show:

<mx:Button label="Icon Button" 
    icon="@Embed(source='c:/myapp/assets/logo.gif')"/>
<mx:Button label="Icon Button" 
    icon="@Embed(source='http://host.com/myapp/assets/logo.gif')"/>

If the path does not start with a slash character, Flex first searches for the file relative to the file that contains the [Embed] metadata tag. For example, the MXML file testEmbed.mxml includes the following code:

<mx:Button label="Icon Button" icon="@Embed(source='assets/logo.gif')"/>

In this example, Flex searches the subdirectory named assets in the directory that contains the testEmbed.mxml file. If the image is not found, Flex then searches for the image in the SWC files associated with the application.

If the path starts with a slash character, Flex first searches the directory of the MXML file for the asset, and then it searches the source path. You specify the source path to the Flex compiler by using the source-path compiler option. For example, you set the source-path option as the following code shows:

-source-path=a1,a2,a3

The MXML file a1/testEmbed.mxml then uses the following code:

<mx:Button label="Icon Button" icon="@Embed(source='/assets/logo.gif')"/>

Flex first searches for the file in a1/assets, then in a2/assets, and then in a3/assets. If the image is not found, Flex searches for the image in the SWC files associated with the application.

If the MXML file is in the a2 directory, as in a2/testEmbed.mxml, Flex first searches the a2 directory and then the directories specified by the source-path option.

About the MIME type

You can optionally specify a MIME type for the imported asset by using the mimeType parameter. If you do not specify a mimeType parameter, Flex makes a best guess about the type of the imported file based on the file extension. If you do specify it, the mimeType parameter overrides the default guess of the asset type.

Flex supports the following MIME types.

• application/octet-stream
• application/x-font
• application/x-font-truetype
• application/x-shockwave-flash
• audio/mpeg
• image/gif
• image/jpeg
• image/png
• image/svg
• image/svg-xml

Using the [Embed] metadata tag

You can use the [Embed] metadata tag to import JPEG, GIF, PNG, SVG, SWF, TTF, and MP3 files.

You must use the [Embed] metadata tag before a variable definition, where the variable is of type Class. The following example loads an image file, assigns it to the imgCls variable, and then uses that variable to set the value of the source property of an Image control:

<?xml version="1.0"?>
<!-- embed\ImageClass.mxml -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" 
    width="100" height="80" borderStyle="solid">
    
    <mx:Script>
        <![CDATA[
            [Embed(source="logo.gif")]
            [Bindable]
            public var imgCls:Class;
        ]]>
    </mx:Script>

    <mx:Image source="{imgCls}"/>
</mx:Application>