Flex 3 中没有等效项.您可以在其他组件旁边声明内容.Flex 4 中的差异使得视觉和非视觉项目(包括效果等、验证器、格式化器、数据声明和 RPC 类)更清晰.

There is no equivalent in Flex 3. You can declare things alongside your other components. The difference in Flex 4 makes the separation between visual and non-visual items (including things like effects, validators, formatters, data declarations, and RPC classes) clearer.

例如，在 Flex 4 中，您可以这样做:

For example, in Flex 4 you would do this:

<?xml version="1.0" encoding="utf-8"?>
<s:Application
    xmlns:fx="http://ns.adobe.com/mxml/2009"
    xmlns:s="library://ns.adobe.com/flex/spark"
    xmlns:mx="library://ns.adobe.com/flex/mx">

    <fx:Declarations>
        <fx:String>Hello, world!</fx:String>
    </fx:Declarations>

    <!-- Component defintions -->

</s:Application>

但在 Flex 3 中，您会这样做:

but in Flex 3, you would do this:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application
    xmlns:mx="http://www.adobe.com/2006/mxml">

    <mx:String>blah</mx:String>

    <!-- Component defintions -->

</mx:Application>

但是，您可以在 <mx:Script> 或

You can, however, define your variables and whatever other declarations (visual or not) within the <mx:Script> or <fx:Script> tag in Flex 3 and 4 respectively.

如果您遇到其他更改，请搜索 Adob​​e 网站关于 从 flex 3 迁移到 flex 4 以查看您可能需要进行哪些其他更改.

If you're stuck on other changes, search Adobe's website about migrating from flex 3 to flex 4 to see what other changes you may have to make.