Error when building with Room: kapt An exception occurred: java.lang.IllegalArgumentException: voidcannot be converted to an Element

Question

When building my project that uses the Room library, Dagger for dependency injection, and Kotlin, I encounter this error:

[kapt] An exception occurred: java.lang.IllegalArgumentException: voidcannot be converted to an Element

Here is my code:

@Entity(tableName = "contacts_table")
data class Contact(@PrimaryKey var cid: Long,
          @ColumnInfo(name = "firstColor") var firstColor: String?,
          @ColumnInfo(name = "secondColor") var secondColor: String?,
          @ColumnInfo(name = "avatarUrl") var avatarUrl: String?,
          @ColumnInfo(name = "name") var name: String,
          @ColumnInfo(name = "nickname") var nickname: String)


@Dao
interface ContactsDao {

     @Insert(onConflict = REPLACE)
     fun insertContact(contact: Contact)

     @Query("delete from contacts_table where cid=:id")
     fun deleteContactById(id: Long)

     @Query("select * from contacts_table")
     fun getAllContacts() : List<Contact>
}


@Database(entities = [Contact::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
     abstract fun contactsDao()
}

Here is an example of how I use my DAO:

contactsDao.insertContact(Contact(response.id, response.firstColor, response.secondColor, 
        null, response.name, response.nickname)) 

contactsDao.insertContact(Contact(response.id, null, null, response.avatarUrl, 
        response.name, response.nickname))

How do I fix this build error?

Answer 1

In your AppDatabase you must specify a return type for contactsDao(). It must be ContactsDao. So, your class should looks as follows:

@Database(entities = [Contact::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {
     abstract fun contactsDao(): ContactsDao
}