Changes the model object visualized by this class to the given one.
The item that should become the model of this class. Must not be
- The proxied version of the given item object, for purposes of data
binding. If you intend to make any changes to the state of the item
after adding it to this widget, you must do so via this returned
proxy. If you modify the item directly (rather than via the proxy)
then this UI widget will not update.