Flex总结--实现文本框的输入下拉提示

<?xml version="1.0" encoding="utf-8"?>
<mx:FormItem xmlns:mx="http://www.adobe.com/2006/mxml"   label="" required="true" width="305" fontWeight="bold" height="28" horizontalAlign="right" textAlign="center" fontStyle="normal">
	
		<mx:Script>
		<!--[CDATA[			
			import mx.managers.PopUpManager;
			import mx.controls.Text;
			import mx.rpc.events.ResultEvent;
			import Scripts.ToolHelper;		
			
			//public var  _win:PortWindow=new PortWindow();
			[Bindable]
			private var PortName:Text=new Text();
			
			private function DropPorts_KeyDown(event:KeyboardEvent):void
				{					
					if(this.DropPorts.editable==false)return;
					this.DropPorts.close();
					if(event.keyCode==Keyboard.ENTER)
					{	
						this.DropPorts.prompt=this.DropPorts.text;
						if(this.DropPorts.text.length<2)return; 
						this.HttpPort.cancel();
						this.HttpPort.url="your url here";
						this.HttpPort.addEventListener(ResultEvent.RESULT,HttpPort_result)	
						this.HttpPort.send();
					}
					else
					{	
					}
				}
			private function HttpPort_result(event:ResultEvent):void
			{
				this.DropPorts.open();
			}	
			]]-->
		</mx:Script>
		
		<mx:HTTPService id="HttpPort" method="GET" />
		<mx:ComboBox id="DropPorts" keyDown="DropPorts_KeyDown(event);" 
			 labelField="Name"
			  dataProvider="{HttpPort.lastResult.CityOcean.Port}" width="170" editable="true" textAlign="left"></mx:ComboBox>
		<mx:Text id="txtPortID" visible="false" height="0"    width="0"    text="{DropPorts.selectedItem.ID}"  />		
		
</mx:FormItem>