How to implement effects in Flex on components creation or removal

I have multiple MXML custom components that I add on the fly (using a repeater) that is binded to an ArrayCollection. So everytime I add/remove item from the ArrayColleciton new items show/disappear from the screen.

Is there a straightforward way to make item fade in when they get created and fade out开发者_如何学运维 when they are removed? I thought of using states and state transition effects but that will make things a bit complicated at different part of my application for those components to manage the states.

You need "Data effects" not "State Transitions". Creating the effect is the same, but the way you set it up is slightly different. Take a look at this list:

http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/mx/core/UIComponent.html?filter_flex=4.1&filter_flashplayer=10.1&filter_air=2#top

Specifically, you'll probably want to use addedEffect when something is added and removedEffect when something is removed. You may also want to investigate hideEffect and showEffect .

So, instead of creating a transitions array, you'll set the effect like it were a style in ActionScript. In MXML, set it like it were a property on the component.

And I strongly recommend not using repeaters if there is any chance your data will scroll off the screen. A repeater will renderer every element in your dataProvider. A list, will only render those elements that display on screen. Lists are much more effecient in this regards.