I am trying to use LiveData for paging data from my Room database. The sample code from Google indicates the use of a toLiveData function:
class ConcertViewModel(concertDao: ConcertDao) : ViewModel() {
val concertList: LiveData<PagedList<Concert>> =
concertDao.concertsByDate().toLiveData(pageSize = 50)
}
https://developer.android.com/topic/libraries/architecture/paging
Here is the code I created that follows their example:
AppDao.kt
import androidx.lifecycle.LiveData
import androidx.paging.DataSource
import androidx.room.Dao
import androidx.room.Insert
import androidx.room.OnConflictStrategy.REPLACE
import androidx.room.Query
import com.example.model.UserConnection
@Dao
interface AppDao {
@Query("SELECT * FROM UserConnection")
fun getAll(): LiveData<List<UserConnection>>
@Insert(onConflict = REPLACE)
fun save(userConnection: UserConnection)
@Query("SELECT * FROM UserConnection ORDER BY firstName DESC")
fun connectionsByFirstName(): DataSource.Factory<Int, UserConnection>
}
AppDatabase.kt
import androidx.room.Database
import androidx.room.RoomDatabase
import androidx.room.TypeConverters
import com.example.model.UserConnection
@Database(entities = arrayOf(UserConnection::class), version = 1, exportSchema = true)
@TypeConverters(RoomConverters::class)
abstract class AppDatabase : RoomDatabase() {
abstract fun appDao(): AppDao
}
ConnectionsViewModel.kt
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import androidx.paging.DataSource
import androidx.paging.PagedList
import com.linkedintools.da.local.room.AppDao
import com.example.model.UserConnection
import javax.inject.Inject
class ConnectionsViewModel @Inject constructor(appDao: AppDao) : ViewModel() {
val connectionsDataSource : DataSource.Factory<Int, UserConnection> = appDao.connectionsByFirstName()
val concertList: LiveData<PagedList<UserConnection>> = connectionsDataSource.toLiveData(pageSize = 40)
}
build.gradle
dependencies {
def room_version = "2.1.0-rc01"
def paging_version = "2.1.0"
implementation "androidx.room:room-runtime:$room_version"
kapt "androidx.room:room-compiler:$room_version" // For Kotlin use kapt instead of annotationProcessor
// optional - Kotlin Extensions and Coroutines support for Room
implementation "androidx.room:room-ktx:$room_version"
// optional - RxJava support for Room
implementation "androidx.room:room-rxjava2:$room_version"
// Paging
implementation "androidx.paging:paging-runtime:$paging_version"
}
The toLiveData is not available. Am I doing something wrong or is the sample code from Google out of date?
