data provider:高级数据绑定

基于ListBase的flex组件从 data provider 获取数据。dataProvider提供了复杂数据类型，如Array，ArrayCollection，XML,XMLCollection等。dataProvider可以用mxml及AS两种方式定义。下面例子中的四个List展现同样的内容：

<? xml version="1.0" encoding="utf-8" ?>
< mx:Application  xmlns:mx ="http://www.adobe.com/2006/mxml"  layout ="horizontal" >
     < mx:Script >
         <![CDATA[
            [Bindable]
            private var myArray:Array = ["a","b","c"];
            
            [Bindable]
            private var xml:XML = 
            <nodes>
                    <node label="a"/>
                <node label="b"/>
                <node label="c"/>
            </nodes>;
         ]]>
     </ mx:Script >
    
     < mx:List  dataProvider ="{myArray}"  width ="50"  height ="200" />
     < mx:List  dataProvider ="{xml.children()}"   labelField ="@label"   width ="50"  height ="200" />
     < mx:List   width ="50"  height ="200" >
         < mx:dataProvider >
             < mx:Object  label ="a" />
             < mx:Object  label ="b" />
             < mx:Object  label ="c" />
         </ mx:dataProvider >
     </ mx:List >
     < mx:List    width ="50"  height ="200"  labelField ="@label" >
         < mx:dataProvider >
         < mx:XMLList >
                 < node  label ="a" />
                 < node  label ="b" />
                 < node  label ="c" />             
         </ mx:XMLList >
            
         </ mx:dataProvider >
     </ mx:List >
    
</ mx:Application >

如果使用Collection，可以保证数据同步并提供简单数据操作,比如排序和过滤。下面的例子演示了同步，排序和过滤：

<? xml version="1.0" encoding="utf-8" ?>
< mx:Application  xmlns:mx ="http://www.adobe.com/2006/mxml"  layout ="horizontal"  creationComplete ="init()" >
     < mx:Script >
         <![CDATA[
            import mx.collections.SortField;
            import mx.collections.Sort;
            import mx.collections.ArrayCollection;
            [Bindable]
            //private var myArray:Array =  ["c","b","a"];
            private var myArray:ArrayCollection = new ArrayCollection( ["c","b","a"]);
            private function sort(){                
                var sort:Sort = new Sort();
                sort.fields = [new SortField()];
                myArray.sort = sort;
                myArray.refresh();
                myArray.sort.fields = new Array();
            }
            
            private function filter(item:Object):Boolean{
                if("a"==item)
                    return false;
                else
                    return true;
            }
         ]]>
     </ mx:Script >
    
     < mx:List  dataProvider ="{myArray}"  width ="50"  height ="200" />
     <!-- <mx:Button label="add" click="myArray.push(myArray.length)"/> -->
     < mx:Button  label ="add"  click ="myArray.addItem(myArray.length)" />
     < mx:Button  label ="sort"  click ="sort()" />
     < mx:Button  label ="filter"  click ="myArray.filterFunction=filter;myArray.refresh();" />
</ mx:Application >