enterState
The State class is a small class that is really only used to define the states of a component. It inherits only from EventDispatcher. State has a three public properties: overrides:Array, basedOn:String, and name:String. overrides holds the operations that the State will perform when it is applied to a component. name sets the name of the state and basedOn established a hierarchy between states.
The enterState event is dispatched from the State class when a new state has been entered. The class that actually dispatches this event is UIComponent. State is actually a very small class that exposes an mx_internal method dispatchEnterState() which UIComponent hijacks since it is in charge of applying states to itself:
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private function applyState(stateName:String, lastState:String):void
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{
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var state:State = getState(stateName);
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if (stateName == lastState)
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return;
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if (state)
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{
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// Apply "basedOn" overrides first
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if (state.basedOn != lastState)
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applyState(state.basedOn, lastState);
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// Apply new state overrides
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var overrides:Array = state.overrides;
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for (var i:int = 0; i < overrides.length; i++)
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overrides[i].apply(this);
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// Dispatch the "enterState" event
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state.dispatchEnterState();
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}
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}
This code is called from commitCurrentState() which is also a private method in UIComponent.
Problem:
You have some custom initialization that you need to perform every time a component is added using a State, such as setting focus in a particular field. You need a reliable method of determining that the component has been added.
Solution:
There are two solutions that I've found to work in this case. This first is to add a new public method to the component called activate() and then call it from a handler on the enterState Event. The second is to listen to the addedToStage and updateComplete events, set a flag in addedToStage that you check in updateComplete to run your initialization.
Here is the code, example app, and more detailed explanation.