Flex 4: State Change Event - actionscript-3

Question

Is there any event in Flex 4 that I can use to detect a state change?

Answer 1

I know this question is old but by googling for state change events I still get here so for people that want to know:
There is a StateChangeEvent.CURRENT_STATE_CHANGE event that is dispatched by the component, so your application can also listen for that.
In your listener function you can then acces the StateChangeEvent.oldState and StateChangeEvent.newState properties.

Answer 2

If you are talking about view states the answer is yes, you can listen for the enterState event like this (sorry for the simplicity of the example, it's part of a project I'm working on and I removed any relevant parts of the code):
<?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/mx"
minWidth="800" minHeight="600"
currentState="loading">
<fx:Script>
<![CDATA[
import mx.controls.Alert;
private function onEnterLoadingState():void{
Alert.show("Enter the loading state.", "Application");
}
private function onEnterLoginState():void{
Alert.show("Enter the login state.", "Application");
}
private function onEnterAddState():void{
Alert.show("Enter the addUser state.", "Application");
}
private function changeState(state:String):void{
currentState = state;
}
]]>
</fx:Script>
<s:states>
<s:State name="loading" enterState="onEnterLoadingState()"/>
<s:State name="login" enterState="onEnterLoginState()"/>
<s:State name="addUser" enterState="onEnterAddState()"/>
</s:states>
<s:Panel id="loadView" includeIn="loading" title="Loading">
<s:Button label="Go to login" click="changeState('login')"/>
</s:Panel>
<s:Panel id="loginView" includeIn="login" title="Login">
<s:Button label="Go to addUser" click="changeState('addUser')"/>
</s:Panel>
<s:Panel id="addView" includeIn="addUser" title="AddUser">
<s:Button label="Return to loading" click="changeState('loading')"/>
</s:Panel>
</s:Application>
And there is an exitState event in case you need it. I hope this helps you.

Answer 3

There are multiple state events you can listen for on any UIComponent class:
FlexEvent.STATE_CHANGE_COMPLETE
FlexEvent.STATE_CHANGE_INTERRUPTED
StateChangeEvent.CURRENT_STATE_CHANGING
StateChangeEvent.CURRENT_STATE_CHANGE
FlexEvent.ENTER_STATE
FlexEvent.EXIT_STATE
MXML:
<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx"
enterState="windowedapplication1_enterStateHandler(event)"
exitState="windowedapplication1_exitStateHandler(event)"
currentStateChange="windowedapplication1_currentStateChangeHandler(event)"
currentStateChanging="windowedapplication1_currentStateChangingHandler(event)"
stateChangeInterrupted="windowedapplication1_stateChangeInterruptedHandler(event)"
stateChangeComplete="windowedapplication1_stateChangeCompleteHandler(event)">
<fx:Script>
<![CDATA[
import mx.events.FlexEvent;
protected function windowedapplication1_stateChangeCompleteHandler(event:FlexEvent):void
{
}
protected function windowedapplication1_stateChangeInterruptedHandler(event:FlexEvent):void
{
}
protected function windowedapplication1_currentStateChangeHandler(event:StateChangeEvent):void
{
var oldState:String = event.oldState;
var newState:String = event.newState;
}
protected function windowedapplication1_currentStateChangingHandler(event:StateChangeEvent):void
{
var oldState:String = event.oldState;
var newState:String = event.newState;
}
protected function windowedapplication1_enterStateHandler(event:FlexEvent):void
{
}
protected function windowedapplication1_exitStateHandler(event:FlexEvent):void
{
}
]]>
</fx:Script>
</s:WindowedApplication>