Kotlin Room+找不到实现DB+DB_Impl不存在

I am getting following error while running application

java.lang.RuntimeException: cannot find implementation for com.abc.db.abdDB. abcDB_Impl does not exist

我的build.gradle配置如下:

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"

我的数据库类:

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
    }

有人try 使用androidX API吗？有人能帮我找到解决这个问题的办法吗？