Error: addChild() is not available in this class. Instead, use addElement() or modify the skin, if you have one. spark.components::Group/addChild
Check if the class is a Group (Group 
GroupBase UIComponent FlexSprite Sprite DisplayObjectContainer InteractiveObject DisplayObject EventDispatcher)
If you want to allow a Group then you should use the addElement method in place of addChild. But if when you do that you get a compiler error, “1061: Call to a possibly undefined method addElement through a reference with static type flash.display:Sprite.” then you will need to type the class to Group which is the first class to contain addElement().
// original code
function test(container:Sprite):void {
container.addChild(displayObject);
}
// changed code
function test(container:Group):void {
container.addElement(displayObject);
}
As long as the class is not a Group you can use the addChild method. If the class is a UIComponent or a subclass (UIComponent FlexSprite Sprite DisplayObjectContainer InteractiveObject DisplayObject EventDispatcher Object) then you can use the addChild method.
If you must use addChild method and must use a Group container add a Sprite container first then use addChild with that.
function test(container:Group):void {
var containerBridge:Sprite = new Sprite(); // SpriteVisualElement?
containerBridge.addChild(displayObject);
container.addElement(containerBridge);
}
If you want to support both then you can use the following code:
if (mySprite is Group) {
Group(mySprite).addElement(displayObject);
}
else {
mySprite.addChild(displayObject);
}
