IssueTracker

Component used: Paging
Version used: 1.0.0-alpha5
Devices/Android versions reproduced on: n/a

Steps to Reproduce: Attempt to call loadInitial() on a PositionalDataSource

Expected Result: For it to be possible to call loadInitial() on a PositionalDataSource

Actual Result:

- We cannot create instances of PositionalDataSource.LoadInitialCallback, because the LoadInitialCallback constructor takes a PageResult.Receiver<T> parameter, and PageResult is not public

- The LoadInitialCallback constructor is not public or protected, so we cannot chain to the superclass in our own LoadInitialCallback subclasses

- The same two problems hold for LoadRangeCallback (depends on PageResult, constructor not public or protected) for calls to loadRange() on a PositionalDataSource

As it stands, we cannot write code to consume a PositionalDataSource, such as those from Room, because we cannot call loadInitial() or loadRange(), because we cannot provide the necessary callbacks.

Workaround: put classes using PositionalDataSource into android.arch.paging, which is really icky