Interface that is implemented to discover when a Loader has been canceled
before it finished loading its data. You do not normally need to implement
this yourself; it is used in the implementation of
to find out when a Loader it is managing has been canceled so that it
can schedule the next Loader. This interface should only be used if a
Loader is not being used in conjunction with LoaderManager.
Called on the thread that created the Loader when the load is canceled.