Run DAO operation on Dispatchers.IO (main) (#432)

* Run DAO operation on Dispatchers.IO.

* Use withContext() to set dispatcher.

* Remove import.

* Fix test.

Author: arriolac

MigrationCodelab/app/src/androidTest/java/com/google/samples/apps/sunflower/viewmodels/PlantDetailViewModelTest.kt

@@ -24,6 +24,7 @@ import com.google.samples.apps.sunflower.data.GardenPlantingRepository
 import com.google.samples.apps.sunflower.data.PlantRepository
 import com.google.samples.apps.sunflower.utilities.getValue
 import com.google.samples.apps.sunflower.utilities.testPlant
+import kotlinx.coroutines.Dispatchers
 import org.junit.After
 import org.junit.Assert.assertFalse
 import org.junit.Before
@@ -45,7 +46,8 @@ class PlantDetailViewModelTest {
 
         val plantRepo = PlantRepository.getInstance(appDatabase.plantDao())
         val gardenPlantingRepo = GardenPlantingRepository.getInstance(
-            appDatabase.gardenPlantingDao()
+            appDatabase.gardenPlantingDao(),
+            Dispatchers.IO
         )
         viewModel = PlantDetailViewModel(plantRepo, gardenPlantingRepo, testPlant.plantId)
     }

MigrationCodelab/app/src/main/java/com/google/samples/apps/sunflower/data/GardenPlantingRepository.kt

@@ -16,13 +16,20 @@
 
 package com.google.samples.apps.sunflower.data
 
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
+
 class GardenPlantingRepository private constructor(
-    private val gardenPlantingDao: GardenPlantingDao
+    private val gardenPlantingDao: GardenPlantingDao,
+    private val ioDispatcher: CoroutineDispatcher
 ) {
 
     suspend fun createGardenPlanting(plantId: String) {
-        val gardenPlanting = GardenPlanting(plantId)
-        gardenPlantingDao.insertGardenPlanting(gardenPlanting)
+        withContext(ioDispatcher) {
+            val gardenPlanting = GardenPlanting(plantId)
+            gardenPlantingDao.insertGardenPlanting(gardenPlanting)
+        }
     }
 
     suspend fun removeGardenPlanting(gardenPlanting: GardenPlanting) {
@@ -39,9 +46,11 @@ class GardenPlantingRepository private constructor(
         // For Singleton instantiation
         @Volatile private var instance: GardenPlantingRepository? = null
 
-        fun getInstance(gardenPlantingDao: GardenPlantingDao) =
+        fun getInstance(gardenPlantingDao: GardenPlantingDao, ioDispatcher: CoroutineDispatcher) =
             instance ?: synchronized(this) {
-                instance ?: GardenPlantingRepository(gardenPlantingDao).also { instance = it }
+                instance ?: GardenPlantingRepository(gardenPlantingDao, ioDispatcher).also {
+                    instance = it
+                }
             }
     }
 }

MigrationCodelab/app/src/main/java/com/google/samples/apps/sunflower/utilities/InjectorUtils.kt

@@ -24,12 +24,15 @@ import com.google.samples.apps.sunflower.data.PlantRepository
 import com.google.samples.apps.sunflower.viewmodels.GardenPlantingListViewModelFactory
 import com.google.samples.apps.sunflower.viewmodels.PlantDetailViewModelFactory
 import com.google.samples.apps.sunflower.viewmodels.PlantListViewModelFactory
+import kotlinx.coroutines.Dispatchers
 
 /**
  * Static methods used to inject classes needed for various Activities and Fragments.
  */
 object InjectorUtils {
 
+    private val ioDispatcher = Dispatchers.IO
+
     private fun getPlantRepository(context: Context): PlantRepository {
         return PlantRepository.getInstance(
             AppDatabase.getInstance(context.applicationContext).plantDao()
@@ -38,7 +41,8 @@ object InjectorUtils {
 
     private fun getGardenPlantingRepository(context: Context): GardenPlantingRepository {
         return GardenPlantingRepository.getInstance(
-            AppDatabase.getInstance(context.applicationContext).gardenPlantingDao()
+            AppDatabase.getInstance(context.applicationContext).gardenPlantingDao(),
+            ioDispatcher
         )
     }