Adding UIComponent to both Canvas and Tree in Flex 3

Question

I currently am trying to add a custom class which subclasses UIComponent to both a tree and a canvas, but when I try to re-order the tree by dragging I get this error:

TypeError: Error #1010: A term is undefined and has no properties. at mx.controls::Tree/get firstVisibleItem()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\controls\Tree.as:764] at flash.utils::ByteArray/writeObject() at flash.desktop::Clipboard/putSerialization() at flash.desktop::Clipboard/convertFlashFormat() at flash.desktop::Clipboard/setData() at mx.managers::NativeDragManagerImpl/doDrag()[C:\autobuild\3.2.0\frameworks\projects\airframework\src\mx\managers\NativeDragManagerImpl.as:282] at mx.managers::DragManager$/doDrag()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\managers\DragManager.as:243] at mx.controls.listClasses::ListBase/dragStartHandler()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\controls\listClasses\ListBase.as:9085] at flash.events::EventDispatcher/dispatchEventFunction() at flash.events::EventDispatcher/dispatchEvent() at mx.core::UIComponent/dispatchEvent()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\core\UIComponent.as:9298] at mx.controls.listClasses::ListBase/mouseMoveHandler()[C:\autobuild\3.2.0\frameworks\projects\framework\src\mx\controls\listClasses\ListBase.as:8822]

When I do not add the UIComponent to the canvas, this error does not occur, anyone have any knowledge as to why this happens?

Answer 1

The reason you are getting this error, the tree or canvas is not able to access your custom components properties or methods. Though your component does get into the display object, but still it does need know on how to access it.

Answer 2

You should create a new instance of your control in order to add it to the canvas. There are numerous properties on a UIComponent that require it to be in one place - the parent property, for example. If you need both to display something similar, you can use a third object to store your state and databind to it.