Change to SingleLiveData

Author: quanda-0562

app/src/main/java/com/example/moviedb/ui/base/BaseViewModel.kt

@@ -1,6 +1,5 @@
 package com.example.moviedb.ui.base
 
-import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.example.moviedb.data.remote.toBaseException
@@ -16,7 +15,7 @@ import java.net.UnknownHostException
 open class BaseViewModel : ViewModel() {
 
     // loading flag
-    val isLoading by lazy { MutableLiveData(false) }
+    val isLoading by lazy { SingleLiveData<Boolean>().apply { value = false } }
 
     // error message
     val errorMessage by lazy { SingleLiveData<String>() }

app/src/main/java/com/example/moviedb/ui/screen/image/ImageViewModel.kt

@@ -1,13 +1,13 @@
 package com.example.moviedb.ui.screen.image
 
-import androidx.lifecycle.MutableLiveData
 import com.example.moviedb.ui.base.BaseViewModel
+import com.example.moviedb.utils.SingleLiveData
 import dagger.hilt.android.lifecycle.HiltViewModel
 import javax.inject.Inject
 
 @HiltViewModel
 class ImageViewModel @Inject constructor() : BaseViewModel() {
 
-    val imageUrl = MutableLiveData<String>()
+    val imageUrl = SingleLiveData<String>()
 
 }

app/src/main/java/com/example/moviedb/ui/screen/moviedetail/MovieDetailViewModel.kt

@@ -1,11 +1,11 @@
 package com.example.moviedb.ui.screen.moviedetail
 
-import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.viewModelScope
 import com.example.moviedb.data.model.Cast
 import com.example.moviedb.data.model.Movie
 import com.example.moviedb.data.repository.UserRepository
 import com.example.moviedb.ui.base.BaseViewModel
+import com.example.moviedb.utils.SingleLiveData
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
@@ -17,9 +17,8 @@ class MovieDetailViewModel @Inject constructor(
     private val userRepository: UserRepository
 ) : BaseViewModel() {
 
-    val movie = MutableLiveData<Movie>()
-    val cast = MutableLiveData<List<Cast>>()
-    private val favoriteChanged = MutableLiveData<Boolean>().apply { value = false }
+    val movie = SingleLiveData<Movie>()
+    val cast = SingleLiveData<List<Cast>>()
 
     fun checkFavorite(id: String) {
         viewModelScope.launch {
@@ -45,8 +44,6 @@ class MovieDetailViewModel @Inject constructor(
         newMovie?.isFavorite = movie.value?.isFavorite != true
         movie.value = newMovie
 
-        favoriteChanged.value = true
-
         newMovie?.let {
             viewModelScope.launch {
                 try {

app/src/main/java/com/example/moviedb/utils/SingleLiveData.kt

@@ -9,6 +9,7 @@ import java.util.concurrent.atomic.AtomicBoolean
  * https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150
  * Description: Custom mutable live data that used for single event
  *              such as navigation (for configuration change), show toast..
+ * NOTE: can has only 1 observer
  */
 class SingleLiveData<T> : MutableLiveData<T>() {