title: Room + cannot find implementation DB + DB_Impl does not exist
body: <p>I am getting following error while running application</p>
  
  <pre><code>java.lang.RuntimeException: cannot find implementation for com.abc.db.abdDB. abcDB_Impl does not exist
  </code></pre>
  
  <p>My build.gradle has following configuration:</p>
  
  <pre><code>implementation "androidx.lifecycle:lifecycle-extensions:2.0.0-alpha1"
  annotationProcessor "androidx.lifecycle:lifecycle-compiler:2.0.0-alpha1"
  implementation "androidx.room:room-runtime:2.0.0-alpha1"
  annotationProcessor "androidx.room:room-compiler:2.0.0-alpha1"
  </code></pre>
  
  <p>My Database class:</p>
  
  <pre><code>fun getDatabase(context: Context): abcDB? {
          if (dbInstance == null) {
              synchronized(abcDB::class.java) {
                  if (dbInstance == null) {
                      dbInstance = Room.databaseBuilder(context.applicationContext,
                              abcDB::class.java, "abc_db")
                              .fallbackToDestructiveMigration()
                              .addCallback(sRoomDatabaseCallback)
                              .build()
                  }
              }
          }
          return dbInstance
      }
  </code></pre>
  
  <p>Does anyone try to use androidX API? Can someone help to find solution for this?</p>