panel

var panel: P? = null

The panel bound to this holder by bindViewHolder.

This panel has to be tracked independently from the panels actually attached to the subContainerView because the subContainerView state cannot always reflect the RecyclerView callbacks we're given. In bindViewHolder we're told which panel belongs within subContainerView, but we cannot actually attach the panel prior to onViewAttachedToWindow. Hence, this property reflects the panel that the sub-container should contain, but doesn't indicate whether it actually does.