[todo-mvp] not find the class RoomDatabase

When I rebuild the project and run it.
It taost not find the class.

Not find the class : Database
Not find the class : RoomDatabase

The package seems not exist.?

android.arch.persistence.room

I click **Poject ---> External Library --->** and find some maybe concern with package Room.

android.arch.persistence.room:migration
android.arch.persistence.room:testing
android.arch.persistence.db
android.arch.persistence.db-framwork

I check out all the package but find no package I look for. and no concerns class.

Maybe some class lost or I open in a wrong posture?

Start by checking the project's external libraries and the android.arch.persistence.room dependencies mentioned in the report, then rebuild the project. Done means the Database and RoomDatabase classes resolve successfully without the reported class-not-found errors.

Written by the indexing model from the issue text.