ChargepriceFragment: avoid reloading prices on orientation change

using SavedStateHandle

app/src/main/java/net/vonforst/evmap/fragment/ChargepriceFragment.kt

@@ -31,7 +31,7 @@ import net.vonforst.evmap.model.Chargepoint
 import net.vonforst.evmap.storage.PreferenceDataSource
 import net.vonforst.evmap.viewmodel.ChargepriceViewModel
 import net.vonforst.evmap.viewmodel.Status
-import net.vonforst.evmap.viewmodel.viewModelFactory
+import net.vonforst.evmap.viewmodel.savedStateViewModelFactory
 import java.text.NumberFormat
 
 class ChargepriceFragment : Fragment() {
@@ -39,10 +39,11 @@ class ChargepriceFragment : Fragment() {
     private var connectionErrorSnackbar: Snackbar? = null
 
     private val vm: ChargepriceViewModel by viewModels(factoryProducer = {
-        viewModelFactory {
+        savedStateViewModelFactory { state ->
             ChargepriceViewModel(
                 requireActivity().application,
-                getString(R.string.chargeprice_key)
+                getString(R.string.chargeprice_key),
+                state
             )
         }
     })

app/src/main/java/net/vonforst/evmap/viewmodel/ChargepriceViewModel.kt

@@ -16,21 +16,25 @@ import net.vonforst.evmap.storage.PreferenceDataSource
 import retrofit2.HttpException
 import java.io.IOException
 
-class ChargepriceViewModel(application: Application, chargepriceApiKey: String) :
+class ChargepriceViewModel(
+    application: Application,
+    chargepriceApiKey: String,
+    private val state: SavedStateHandle
+) :
     AndroidViewModel(application) {
     private var api = ChargepriceApi.create(chargepriceApiKey)
     private var prefs = PreferenceDataSource(application)
 
     val charger: MutableLiveData<ChargeLocation> by lazy {
-        MutableLiveData<ChargeLocation>()
+        state.getLiveData("charger")
     }
 
     val dataSource: MutableLiveData<String> by lazy {
-        MutableLiveData<String>()
+        state.getLiveData("dataSource")
     }
 
     val chargepoint: MutableLiveData<Chargepoint> by lazy {
-        MutableLiveData<Chargepoint>()
+        state.getLiveData("chargepoint")
     }
 
     private val vehicleIds: MutableLiveData<Set<String>> by lazy {
@@ -65,7 +69,7 @@ class ChargepriceViewModel(application: Application, chargepriceApiKey: String)
     }
 
     val vehicle: MutableLiveData<ChargepriceCar> by lazy {
-        MutableLiveData<ChargepriceCar>()
+        state.getLiveData("vehicle")
     }
 
     val vehicleCompatibleConnectors: LiveData<List<String>> by lazy {
@@ -111,9 +115,9 @@ class ChargepriceViewModel(application: Application, chargepriceApiKey: String)
         }
     }
 
-    val chargePrices: MediatorLiveData<Resource<List<ChargePrice>>> by lazy {
+    val chargePrices: MutableLiveData<Resource<List<ChargePrice>>> by lazy {
         MediatorLiveData<Resource<List<ChargePrice>>>().apply {
-            value = Resource.loading(null)
+            value = state["chargePrices"] ?: Resource.loading(null)
             listOf(
                 charger,
                 dataSource,
@@ -122,10 +126,14 @@ class ChargepriceViewModel(application: Application, chargepriceApiKey: String)
                 vehicleCompatibleConnectors,
                 myTariffs, myTariffsAll
             ).forEach {
-                addSource(it) {
+                addSource(it.distinctUntilChanged()) {
                     if (!batteryRangeSliderDragging.value!!) loadPrices()
                 }
             }
+            observeForever {
+                // persist data in case fragment gets recreated
+                state["chargePrices"] = it
+            }
         }
     }
 

app/src/main/java/net/vonforst/evmap/viewmodel/Utils.kt

@@ -19,6 +19,16 @@ inline fun <VM : ViewModel> viewModelFactory(crossinline f: () -> VM) =
         override fun <T : ViewModel> create(aClass: Class<T>): T = f() as T
     }
 
+@Suppress("UNCHECKED_CAST")
+inline fun <VM : ViewModel> savedStateViewModelFactory(crossinline f: (SavedStateHandle) -> VM) =
+    object : AbstractSavedStateViewModelFactory() {
+        override fun <T : ViewModel> create(
+            key: String,
+            modelClass: Class<T>,
+            handle: SavedStateHandle
+        ) = f(handle) as T
+    }
+
 enum class Status {
     SUCCESS,
     ERROR,