本文转自 ?flex 常用元标签讲解
? ? Flex?引入了元数据标签的概念，大多数人都使用过的?[Bindable]?标签便是其中的?meta tag?之一，它在代码中的作用就是向编译器提供如何编译程序的信息。实际上，这些标签并没有被编译到生成的?SWF?文件中，而只是告诉编译器如何生成?SWF?文件。
adobe?官网?http://livedocs.adobe.com/flex/3/html/help.html?content=metadata_3.html详细讲解了?16种meta?的使用，简单如下表所示。
| Tag |
Description |
| [ArrayElementType] |
Defines the allowed data type of each element of an Array. |
| [Bindable] |
Identifies a property that you can use as the source of a data binding expression. |
| [DefaultProperty] |
Defines the name of the default property of the component when you use the component in an MXML file. |
| [Deprecated] |
Marks a class or class element as deprecated so that the compiler can recognize it and issue a warning when the element is used in an application. |
| [Effect] |
Defines the MXML property name for the effect. |
| [Embed] |
Imports JPEG,GIF,PNG,SVG,and SWF files at compile time. Also imports image assets from SWC files. |
| [Event] |
Defines the MXML property for an event and the data type of the event object that a component emits. |
| [Exclude] |
Omits the class element from the Flex Builder tag inspector. The syntax is as follows:[Exclude(name="label",kind="property")] |
| [ExcludeClass] |
Omits the class from the Flex Builder tag inspector. This is equivalent to the @private tag in ASDoc when applied to a class. |
| [IconFile] |
Identifies the filename for the icon that represents the component in the Insert bar of Adobe Flex Builder. |
| [Inspectable] |
Defines an attribute exposed to component users in the attribute hints and Tag inspector of Flex Builder. Also limits allowable values of the property. |
| [InstanceType] |
Specifies the allowed data type of a property of type IDeferredInstance. |
| [NonCommittingChangeEvent] |
Identifies an event as an interim trigger. |
| [RemoteClass] |
Maps the ActionScript object to a Java object. |
| [Style] |
Defines the MXML property for a style property for the component. |
| [Transient] |
Identifies a property that should be omitted from data that is sent to the server when an ActionScript object is mapped to a Java object using [RemoteClass]. |
???????本人认为，这其中常用的?Bindable?，?Embed?，?RemoteClass?这?3?种（本人是从开发业务程序角度来考虑，?effect?等?ui?效果就暂且忽略了）。
1、??Bindable?标签
Bindable?标签应该是使用率最高的标签，其功效就是将某个变量或者属性绑定到目标对象上，比如业务应用经常要操作?datagrid?，此时就需将变量绑定到?datagrid.dataprovider?上，通过变量操作来显示?datagrid?的数据变动。
????[?Bindable?]
private?var?transWayLists:ArrayCollection;
...
<mx:AdvancedDataGrid dataProvider="{?transWayLists?}"/>
2、??RemoteClass?标签
该标签用以映射?flex object?到?java object?，因此在写?flex?程序与?java?程序交互之时特别有用，比如?flex?登录程序总需发送登录信息到?java?登录服务，然后?java?登录服务通过验证返回登录用户信息，此时就需?flex user映射到?java user?，如下：
flex?：
Bindable?]
????[RemoteClass?(?alias="com.?marcus?.User"?)]
????public?class?User
????{
???????public?var???userId:String;
var?businessId:String;
var???userName:String;
var?password:String;
var?passTimeout:Date;
????...
}
java:
package com.marcus;
import java.util.Date;
public class User {
????private String userId;
????private String businessId;
????private String userName;
????private String password;
????private Date passTimeout;
3、??Embed?标签
该标签用以嵌入?jpg?等资源文件，并在编译的时候生成到?swf?文件中，因此嵌入资源文件过大时，会影响swf?加载速度。
[Embed(source='home.png')]??????//?绑定图片home.png?给home_icon?类
private var home_icon:Class;
?
4、??ArrayElementType?标签
该标签用以标识数组中元素的数据类型，该?meta tag?并未列入本人的常用?meta tag?之一，为何还要强调的原因就是本人认为?ArrayElementType?标签就是一个鸡肋标签，狗屁不是，建议大家慎用。
