Convert FavoritesViewModel to kotlin and optimise code

app/build.gradle

@@ -182,6 +182,8 @@ dependencies {
     def core_version = "1.6.0-beta01"
     implementation "androidx.core:core:$core_version"
 
+    implementation "androidx.fragment:fragment-ktx:1.3.4"
+
     // Room
     def room_version = "2.3.0"
     implementation "androidx.room:room-runtime:$room_version"

app/src/main/java/awais/instagrabber/fragments/FavoritesFragment.kt

@@ -7,17 +7,14 @@ import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
-import androidx.lifecycle.ViewModelProvider
+import androidx.fragment.app.viewModels
 import androidx.navigation.fragment.NavHostFragment
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
 import awais.instagrabber.R
 import awais.instagrabber.adapters.FavoritesAdapter
 import awais.instagrabber.databinding.FragmentFavoritesBinding
-import awais.instagrabber.db.datasources.FavoriteDataSource
 import awais.instagrabber.db.entities.Favorite
-import awais.instagrabber.db.repositories.FavoriteRepository
-import awais.instagrabber.db.repositories.RepositoryCallback
 import awais.instagrabber.models.enums.FavoriteType
 import awais.instagrabber.utils.extensions.TAG
 import awais.instagrabber.viewmodels.FavoritesViewModel
@@ -28,16 +25,9 @@ class FavoritesFragment : Fragment() {
 
     private lateinit var binding: FragmentFavoritesBinding
     private lateinit var root: RecyclerView
-    private lateinit var favoritesViewModel: FavoritesViewModel
-    private lateinit var favoriteRepository: FavoriteRepository
     private lateinit var adapter: FavoritesAdapter
 
-    override fun onCreate(savedInstanceState: Bundle?) {
-        super.onCreate(savedInstanceState)
-        val context = context ?: return
-        favoriteRepository = FavoriteRepository.getInstance(FavoriteDataSource.getInstance(context))
-        favoritesViewModel = ViewModelProvider(this).get(FavoritesViewModel::class.java)
-    }
+    private val favoritesViewModel: FavoritesViewModel by viewModels()
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
         if (this::root.isInitialized) {
@@ -61,13 +51,6 @@ class FavoritesFragment : Fragment() {
         if (!this::adapter.isInitialized) return
         // refresh list every time in onViewStateRestored since it is cheaper than implementing pull down to refresh
         favoritesViewModel.list.observe(viewLifecycleOwner, { list: List<Favorite?>? -> adapter.submitList(list) })
-        favoriteRepository.getAllFavorites(object : RepositoryCallback<List<Favorite>> {
-            override fun onSuccess(favorites: List<Favorite>) {
-                favoritesViewModel.list.postValue(favorites)
-            }
-
-            override fun onDataNotAvailable() {}
-        })
     }
 
     private fun init() {
@@ -109,22 +92,7 @@ class FavoritesFragment : Fragment() {
             val context = context ?: return@FavoritesAdapter false
             MaterialAlertDialogBuilder(context)
                 .setMessage(getString(R.string.quick_access_confirm_delete, model.query))
-                .setPositiveButton(R.string.yes) { d: DialogInterface, _: Int ->
-                    favoriteRepository.deleteFavorite(model.query, model.type, object : RepositoryCallback<Void> {
-                        override fun onSuccess(result: Void) {
-                            d.dismiss()
-                            favoriteRepository.getAllFavorites(object : RepositoryCallback<List<Favorite>> {
-                                override fun onSuccess(result: List<Favorite>) {
-                                    favoritesViewModel.list.postValue(result)
-                                }
-
-                                override fun onDataNotAvailable() {}
-                            })
-                        }
-
-                        override fun onDataNotAvailable() {}
-                    })
-                }
+                .setPositiveButton(R.string.yes) { d: DialogInterface, _: Int -> favoritesViewModel.delete(model) { d.dismiss() } }
                 .setNegativeButton(R.string.no, null)
                 .show()
             true

app/src/main/java/awais/instagrabber/viewmodels/FavoritesViewModel.kt

@@ -1,19 +1,48 @@
-package awais.instagrabber.viewmodels;
+package awais.instagrabber.viewmodels
 
-import androidx.lifecycle.MutableLiveData;
-import androidx.lifecycle.ViewModel;
+import android.app.Application
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import awais.instagrabber.db.datasources.FavoriteDataSource
+import awais.instagrabber.db.entities.Favorite
+import awais.instagrabber.db.repositories.FavoriteRepository
+import awais.instagrabber.db.repositories.RepositoryCallback
 
-import java.util.List;
+class FavoritesViewModel(application: Application) : AndroidViewModel(application) {
+    private val _list = MutableLiveData<List<Favorite>>()
+    val list: LiveData<List<Favorite>> = _list
 
-import awais.instagrabber.db.entities.Favorite;
+    private val favoriteRepository: FavoriteRepository = FavoriteRepository.getInstance(FavoriteDataSource.getInstance(application))
 
-public class FavoritesViewModel extends ViewModel {
-    private MutableLiveData<List<Favorite>> list;
+    init {
+        fetch()
+    }
+
+    fun fetch() {
+        favoriteRepository.getAllFavorites(object : RepositoryCallback<List<Favorite>> {
+            override fun onSuccess(favorites: List<Favorite>?) {
+                _list.postValue(favorites ?: emptyList())
+            }
+
+            override fun onDataNotAvailable() {}
+        })
+    }
+
+    fun delete(favorite: Favorite, onSuccess: () -> Unit) {
+        favoriteRepository.deleteFavorite(favorite.query, favorite.type, object : RepositoryCallback<Void> {
+            override fun onSuccess(result: Void?) {
+                onSuccess()
+                favoriteRepository.getAllFavorites(object : RepositoryCallback<List<Favorite>> {
+                    override fun onSuccess(result: List<Favorite>?) {
+                        _list.postValue(result ?: emptyList())
+                    }
+
+                    override fun onDataNotAvailable() {}
+                })
+            }
 
-    public MutableLiveData<List<Favorite>> getList() {
-        if (list == null) {
-            list = new MutableLiveData<>();
-        }
-        return list;
+            override fun onDataNotAvailable() {}
+        })
     }
-}
+}