A data-binding watcher invokes an event listener when a binding occurs.

           

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<!-- binding/DetectWatcher.mxml -->
<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"
    initialize="initWatcher();">
    <s:layout>
        <s:VerticalLayout />
    </s:layout>
    <fx:Script>
         
            import mx.binding.utils.*; 
            import mx.events.FlexEvent; 
            import mx.events.PropertyChangeEvent; 
            public var myWatcher:ChangeWatcher; 
            // Define binding watcher. 
            public function initWatcher():void { 
                // Define a watcher for the text binding. 
                ChangeWatcher.watch(textarea, "text", watcherListener); 
            } 
            // Event listener when binding occurs. 
            public function watcherListener(event:Event):void { 
                myTA1.text="binding occurred"; 
                // Use myWatcher.unwatch() to remove the watcher. 
            } 
          
    </fx:Script>
    <!-- Define a binding expression to watch. -->
    <s:TextInput id="textinput" text="Hello" />
    <s:TextArea id="textarea" text="{textinput.text}" />
    <!-- Trigger a binding. -->
    <s:Button label="Submit" click="textinput.text='Goodbye';" />
    <s:TextArea id="myTA1" />
</s:Application>

1.	Change event for List control
2.	Adding an event listener if one isn't present
3.	Event listener in an ActionScript function in an tag
4.	List change event
5.	Get selected item from a list from change event
6.	Convert event target to List control
7.	Write your event listener to access the event object
8.	List dragOver, dragDrop, dragExit events
9.	List double click event
10.	Add an Event Listener in MXML

A data-binding watcher invokes an event listener when a binding occurs. : List Event « Components « Flex

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