Flex: Difference between event.target and event.currentTarget properties in an event object.

In Flex, an event object is created whenever an event is dispatched. The event object has two important properties – event.target and event.currentTarget. The event.target property references the event dispatcher while event.currentTarget property refers to the node which is currently being checked for event listeners. While event.target property stays the same throughout the event flow (capturing, targeting and bubbling phases), the event.currentTarget property changes on each node.

For example, if an event is fired from a TextInput component placed inside a Panel, event.target in this case will be TextInput throughout the event flow while event.currentTarget will vary from Application to Panel to TextInput as the event object goes up or down the flow chain.

An important point to note over here is that when an event is fired from a component, event.target property does not necessarily reference the component which dispatched the event. It may refer to a subcomponent which is part of that component. This means that if you click on a button’s label, the event object’s event.target property won’t be button (as you might have hoped) but will be a subcomponent (within the button class) – UITextField (renders label in a button).This is a very important point while handling events. In this case, if the button component was listening for the click event, the event handler will be called if you are using event.currentTarget property since (sooner or later) event.currentTarget will refer to the button component as the mouse event bubbles through the chain. But, if you were using event.target property, the event handler will never get called as a subcomponent (UITextField) fired the event and is referred to in event.target property. Hence, you should always use event.currentTarget property instead of event.target.