使用IDeferredInstance延迟FLEX3组件创建

使用IDeferredInstance延迟FLEX3组件创建

模板组件可以延迟创建，这样就可以让FLEX3只加载用户目前能够看见的组件，从而大大减轻了应用程序的内存占用情况。这是FLEX3的一个新特性，值得大家关注

因为FLEX只在用户需要的时候才创建相应的UI组件实例。通过这一方法，你就可以大大的优化你的应用程序的性能

要使用这项特性，IDeferredInstance应用接口定义了getInstance方法在创建组件的实例的时候用来初始化组件的各项属性，然后据此你创建的组件就可以和下面的例子一样延迟调用。

<?xmlversion="1.0"?>

<mx:VBoxxmlns:mx="http://www.adobe.com/2006/mxml"

initialize="draw();">

<mx:Script>

<![CDATA[

importmx.controls.Image;

importmx.core.UIComponent;

importmx.core.IDeferredInstance;

publicvarheader:IDeferredInstance;

publicvarfooter:IDeferredInstance;

//为一行的组件定义一组属性

[ArrayElementType("mx.core.IDeferredInstance")]

publicvarcontent:Array;

privatefunctiondraw():void...{

addChild(UIComponent(header.getInstance()));

for(vari:int=0;i<content.length;i++)

...{

varmyHeader:UIComponent=

UIComponent(content[i].getInstance());

varmyContent:UIComponent=

UIComponent(header.getInstance());

addChild(myHeader);

addChild(myContent);

}

]]>

</mx:Script>

</mx:VBox>

当你使用IdeferredInstance 作为一个数据类型，你可以为其属性设置任意类型的数据，在addChild方法中可以进行显式的类型转换。

代码中的header, footer, 和content作为UICOMPONENT的参数，因为addChild方法能偶添加一个实现了UICOMPONENT接口的对象作为最暗，所以这样的转换是必须的。

The deferred creation in Flex 3 components using the IDeferredInstance

Starting from the post "Creating template components in Flex 3 and AIR", I've added further information on how to use the IDeferredInstance interface in Flex 3.

Template components can also be created by using the deferred creation feature, which

enables Flex 3 to load only the controls that initially appear to the user who loads the application.

With this approach you can optimize startup performance because Flex 3 loads the

components and their properties only when the user requires them.

The IdeferredInstance interface defines the getInstance() method to initialize the

property when it creates an instance of the component. This method returns a value of

Object type. The MXML component that you previously created could thus become the

following:

<?xml version="1.0"?>

<mx:VBox xmlns:mx="http://www.adobe.com/2006/mxml"

initialize="draw();">

<mx:Script>

<![CDATA[

import mx.controls.Image;

import mx.core.UIComponent;

import mx.core.IDeferredInstance;

public var header:IDeferredInstance;

public var footer:IDeferredInstance;

// Define an Array of properties for a row of components.

[ArrayElementType("mx.core.IDeferredInstance")]

public var content:Array;

private function draw():void {

addChild(UIComponent(header.getInstance()));

for (var i:int = 0; i < content.length; i++)

{

var myHeader:UIComponent =

UIComponent(content[i].getInstance());

var myContent:UIComponent =

UIComponent(header.getInstance());

addChild(myHeader );

addChild(myContent );

}

]]>

</mx:Script>

</mx:VBox>

When you use the IdeferredInstance interface as a data type, you can send any data type

to the property. In the addChild() method, you have carried out an implicit cast by sending

the header, footer, and content properties as arguments of the UIComponent. This

casting is necessary because the addChild() method can add an object that implements

the UIComponent interface to a container.

源文档 <http://casario.blogs.com/mmworld/2008/02/the-deferred-cr.html>