Preserve map traffic enabled state across app restarts

like map type, which was implemented in 6cb682f0

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

@@ -732,6 +732,7 @@ class MapFragment : Fragment(), OnMapReadyCallback, MapsActivity.FragmentCallbac
             }
         }
         map.setMapType(vm.mapType.value)
+        map.setTrafficEnabled(vm.mapTrafficEnabled.value ?: false)
 
         // set padding so that compass is not obstructed by toolbar
         map.setPadding(0, binding.toolbarContainer.height, 0, 0)

app/src/main/java/net/vonforst/evmap/storage/PreferenceDataSource.kt

@@ -80,6 +80,12 @@ class PreferenceDataSource(val context: Context) {
             sp.edit().putString("map_type", type.toString()).apply()
         }
 
+    var mapTrafficEnabled: Boolean
+        get() = sp.getBoolean("map_traffic_enabled", false)
+        set(value) {
+            sp.edit().putBoolean("map_traffic_enabled", value).apply()
+        }
+
     var welcomeDialogShown: Boolean
         get() = sp.getBoolean("welcome_dialog_shown", false)
         set(value) {

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

@@ -217,7 +217,10 @@ class MapViewModel(application: Application, geApiKey: String) : AndroidViewMode
 
     val mapTrafficEnabled: MutableLiveData<Boolean> by lazy {
         MutableLiveData<Boolean>().apply {
-            value = false
+            value = prefs.mapTrafficEnabled
+            observeForever {
+                prefs.mapTrafficEnabled = it
+            }
         }
     }