如何在 Activity 中填充没有 RecyclerView 的 Room 数据库

Question

I would like to populate Room database when open first Activity in onCreate method. I am following tutorial where they use RecyclerView. But I just don't need to see data in RecyclerView at the beginning. How can I populate database withou using RecyclerView.

RestaurantRepository.kt

class RestaurantRepository @Inject constructor(
    private val api: RestaurantApi,
    private val db: SybaseDatabase
) {
    private val restaurantDao = db.restaurantDao()

    fun getRestaurants() = networkBoundResource(
        query = {
            restaurantDao.getAllRestaurants()
        },
        fetch = {
            delay(2000)
            api.getRestaurants()
        },
        saveFetchResult = { restaurants ->
            db.withTransaction {
                restaurantDao.deleteAllRestaurants()
                restaurantDao.insertRestaurants(restaurants)
            }

        }
    )
}

RestaurantViewModel.kt

@HiltViewModel
class RestaurantViewModel @Inject constructor(
    repository: RestaurantRepository
):ViewModel() {
    val restaurants = repository.getRestaurants().asLiveData()

And RestaurantActivity.kt

@AndroidEntryPoint
class RestaurantActivity : AppCompatActivity() {

    private val viewModel: RestaurantViewModel by viewModels()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = ActivityRestaurantBinding.inflate(layoutInflater)
        setContentView(binding.root)

        val restaurantAdapter = RestaurantAdapter()
        binding.apply {
            recyclerView.apply {
                adapter = restaurantAdapter
                layoutManager = LinearLayoutManager(this@RestaurantActivity)
            }
            viewModel.restaurants.observe(this@RestaurantActivity) { result ->
                restaurantAdapter.submitList(result.data)

                progressBar.isVisible = result is Resource.Loading && result.data.isNullOrEmpty()
                textViewErrorr.isVisible = result is Resource.Error && result.data.isNullOrEmpty()
                textViewErrorr.text = result.error?.localizedMessage

            }
        }
    }
}

EDIT: Dao.kt

Import androidx.room.Dao
import androidx.room.Insert
import androidx.room.OnConflictStrategy
import androidx.room.Query
import kotlinx.coroutines.flow.Flow

@Dao
interface SybaseDao {

@Insert(onConflict = OnConflictStrategy.REPLACE)
suspend fun insertRestaurants(restaurant: List<Restaurant>)

@Query("DELETE FROM restaurants")
suspend fun deleteAllRestaurants()

@Query("SELECT * FROM restaurants")
fun getAllRestaurants(): Flow<List<Restaurant>>

This is model class

import androidx.room.Entity
import androidx.room.PrimaryKey

@Entity(tableName = "restaurants")
data class Restaurant (
    @PrimaryKey val name: String,
    val type: String,
    val logo: String,
    val address: String
)

Actually I have more model classes but they look similar. What I want is to first populate the database and in other Activity I want to recieve data to RecyclerView. I will have like three activities with different RecyclerViews and when user chose the item then new activity is started with data from different table.

Answer 1

If you just don't want to load the data from database in your activity, you can change your observer code.

This is your observer code.

viewModel.restaurants.observe(this@RestaurantActivity) { result ->
                restaurantAdapter.submitList(result.data)

                progressBar.isVisible = result is Resource.Loading && result.data.isNullOrEmpty()
                textViewErrorr.isVisible = result is Resource.Error && result.data.isNullOrEmpty()
                textViewErrorr.text = result.error?.localizedMessage

            }

This line is responsible for loading the data into your RecyclerView adapter. If you omit this line you will have an empty activity in your case.

restaurantAdapter.submitList(result.data)

Remember, result cotains the data from your database which is a List in this case. In fact you should remove the observer code if you don't have to use the data in your activity.

Since you further want to populate your database in the onCreate of first activity. You will require List(say allRestaurants) data you want to insert in the database. You will have to create methods in viewmodel and repository which will insert the data into database.

You will call the viewmodel's method like:

viewModel.insertAllRestaurants(allRestaurants)

Inside your viewmodel, you will have to call repository's method for inserting the data.

fun insertAllRestaurants(allRestaurants:List<Restaurant>)
{
  repository.insertAllRestaurants(allRestaurants)
}

Inside your repository, you will have to invoke your insertRestaurants(restaurant: List<Restaurant>) .