Flex Event标签

发布时间：2020-12-15 01:07:24 所属栏目：百科来源：网络整理

导读：Using the Event metadata tag You use the [Event] metadata tag to define events dispatched by a component so that the Flex compiler can recognize them as MXML tag attributes in an MXML file. You add the [Event] metadata tag in one of the fo

Using the Event metadata tag
You use the [Event] metadata tag to define events dispatched by a component so that the Flex compiler can recognize
them as MXML tag attributes in an MXML file. You add the [Event] metadata tag in one of the following locations:
ActionScript components?? Above the class definition,but within the package definition,so that the events are bound
to the class and not a particular member of the class.
MXML components?? In the <mx:Metadata> tag of an MXML file.

Demo：

定义MyEvent extends Event

ActionScript 3语言:

 
 package 
  event 
 
{ 
 
 ? 
 import 
  flash.events.Event; 
 

 ? 
 public 
  class 
 MyEvent 
  extends 
 Event 
 
 ? 
 { 
 
 ??? 
 public 
  static 
 const 
  EVENT_TEST 
 : 
 String 
 = 
 "EventTest"; 
 

 ??? 
 public 
  function  
 MyEvent( 
 type 
 : 
 String 
 , 
 bubbles 
 : 
 Boolean 
 = 
 false 
 , 
 cancelable 
 : 
 Boolean 
 = 
 false) 
 
 ??? 
 { 
 
 ????? 
 super( 
 type 
 , 
 bubbles 
 , 
  cancelable); 
 
 ??? 
 } 
 
 ? 
 } 
 
} 

定义MyButton extends Button

MXML语言:

 
  <?xml version="1.0" encoding="utf-8"?> 
  
<s:Button 
   xmlns:fx= 
  "http://ns.adobe.com/mxml/2009" 
  
 ????? 
  xmlns:s= 
  "library://ns.adobe.com/flex/spark" 
  
 ????? 
  xmlns:mx= 
  "library://ns.adobe.com/flex/halo" 
  
 ????? 
  click= 
  "dispatchEvent(new MyEvent(MyEvent.EVENT_TEST));" 
  > 
  
 ? 
  <fx:Script> 
  
 ??? 
  <![CDATA[ 
  
 ????? 
  import 
   event.MyEvent; 
  
 ??? 
  ]]> 
  
 ? 
  </fx:Script> 
  
 ? 
  <fx:Metadata> 
  
 ????? 
  <!--在Metadata标签下定义Event编译期间检查--> 
  
??????? [Event(name ="EventTest",type ="event.MyEvent")] 
  
 ? 
  </fx:Metadata> 
  
</s:Button> 
  

Main App

MXML语言:

 
  <?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/halo" 
  
 ???????? 
  xmlns:my= 
  "button.*" 
  
 ???????? 
  minWidth= 
  "1024" 
  
 ???????? 
  minHeight= 
  "768" 
  > 
  
 ? 
  <fx:Script> 
  
 ??? 
  <![CDATA[ 
  
 ????? 
  import 
   event.MyEvent; 
  
 ????? 
  /** 
  
?????? * 定义Event的函数监听方式 
  
?????? * 在my2 的 EventTest="handleEvent(event)" 相当于对于该Event注册了一个Listiner 
  
?????? * 消息监听函数为handleEvent(event) 
  
?????? */ 
  
 ????? 
  private 
   function  
  handleEvent( 
  e 
  : 
  MyEvent 
  ): 
  void 
  { 
  trace( 
  e); 
   } 
  
 ??? 
  ]]> 
  
 ? 
  </fx:Script> 
  
 ? 
  <!--可以直接定义EventTest="myTa.text='got Event';" 及在Event触发式执行myTa.text='got Event';--> 
  
 ? 
  <my:MyButton 
   id= 
  "my1" 
  EventTest= 
  "myTa.text='got Event';" 
  x= 
  "208" 
   y= 
  "213" 
  ></my:MyButton> 
  
 ? 
  <my:MyButton 
   id= 
  "my2" 
  EventTest= 
  "handleEvent(event)" 
  x= 
  "209" 
   y= 
  "258" 
  ></my:MyButton> 
  
 ? 
  <s:TextArea 
   id= 
  "myTa" 
  x= 
  "141" 
  y= 
  "55" 
  /> 
  
</s:Application> 
  

解释：

1· 在MyButton中将[Event]标签放入Metadata标签中，则告诉编译器该空间会产生该种Event，

?? 如果此时dispatchEvent出去的Event不是该种类型则在编译期间及会报错。

2· 在主类中<my:MyButton id="my1" EventTest="myTa.text='got Event';" x="208" y="213"></my:MyButton>

?? 由于EventTest已经在Metadata做了标记，即可使用代码提示功能找到相应的Event。

?? EventTest="myTa.text='got Event';"? 表示为EventTest 这个Event注册一个监听者，监听到信息后处理方式为

?? myTa.text='got Event' ， same as the EventTest="handleEvent(event)

（编辑：李大同）

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