Materialized view became INVALID and USER_MVIEWS.COMPILE_STATE becomes 'NEEDS_COMPILE'
That is the expected behaviour. 

If the data in the base table changes and the view isn't up to date anymore its status is not valid anymore. If you recompile or refresh it will become up to date and is valid again. So you don't have to bother about the invalid state of your view.

This question was already posed on stackoverfow.com and answered by Andrew Brennan:


  See MOS Doc ID 264036.1:
  
  
    Dependencies related to MVs are automatically maintained to ensure
    correct operation. When an MV is created, the materialized view
    depends on the master tables referenced in its definition. Any DML
    operation, such as an INSERT, or DELETE, UPDATE, or DDL operation on
    any dependency in the materialized view will cause it to become
    invalid.