Remember low priority expand status across restarts

vector/src/main/java/im/vector/riotx/features/home/room/list/RoomListFragment.kt

@@ -96,6 +96,12 @@ class RoomListFragment @Inject constructor(
         super.onPrepareOptionsMenu(menu)
     }
 
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+
+        context?.let { roomListViewModel.initWithContext(it, roomListParams.displayMode) }
+    }
+
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
         setupCreateRoomButton()
@@ -118,6 +124,14 @@ class RoomListFragment @Inject constructor(
                 .disposeOnDestroyView()
     }
 
+    override fun onPause() {
+        super.onPause()
+
+        withState(roomListViewModel) {
+            state -> context?.let { state.persistWithContext(it, roomListParams.displayMode) }
+        }
+    }
+
     override fun showFailure(throwable: Throwable) {
         showErrorInSnackbar(throwable)
     }

vector/src/main/java/im/vector/riotx/features/home/room/list/RoomListViewModel.kt

@@ -16,6 +16,7 @@
 
 package im.vector.riotx.features.home.room.list
 
+import android.content.Context
 import com.airbnb.mvrx.FragmentViewModelContext
 import com.airbnb.mvrx.MvRxViewModelFactory
 import com.airbnb.mvrx.ViewModelContext
@@ -61,6 +62,13 @@ class RoomListViewModel @Inject constructor(initialState: RoomListViewState,
         observeMembershipChanges()
     }
 
+    fun initWithContext(context: Context, displayMode: RoomListDisplayMode) {
+        setState {
+            // RoomListViewState.initWithContext
+            this.initWithContext(context, displayMode)
+        }
+    }
+
     override fun handle(action: RoomListAction) {
         when (action) {
             is RoomListAction.SelectRoom                  -> handleSelectRoom(action)

vector/src/main/java/im/vector/riotx/features/home/room/list/RoomListViewState.kt

@@ -16,7 +16,10 @@
 
 package im.vector.riotx.features.home.room.list
 
+import android.content.Context
+import android.content.SharedPreferences
 import androidx.annotation.StringRes
+import androidx.preference.PreferenceManager
 import com.airbnb.mvrx.Async
 import com.airbnb.mvrx.MvRxState
 import com.airbnb.mvrx.Uninitialized
@@ -41,8 +44,31 @@ data class RoomListViewState(
         val isServerNoticeRoomsExpanded: Boolean = true
 ) : MvRxState {
 
+    companion object {
+        const val ROOM_LIST_ROOM_EXPANDED_LOW_PRIORITY_PREFIX = "ROOM_LIST_ROOM_EXPANDED_LOW_PRIORITY_"
+    }
+
     constructor(args: RoomListParams) : this(displayMode = args.displayMode)
 
+    private fun getSharedPreferences(context: Context): SharedPreferences {
+        return PreferenceManager.getDefaultSharedPreferences(context)
+    }
+    private fun getRoomListExpandedLowPriorityPref(displayMode: RoomListDisplayMode): String {
+        return ROOM_LIST_ROOM_EXPANDED_LOW_PRIORITY_PREFIX + displayMode.toString()
+    }
+
+    fun initWithContext(context: Context, displayMode: RoomListDisplayMode): RoomListViewState {
+        val sp = getSharedPreferences(context)
+        val pref = getRoomListExpandedLowPriorityPref(displayMode)
+        return copy(isLowPriorityRoomsExpanded = sp.getBoolean(pref, isLowPriorityRoomsExpanded))
+    }
+
+    fun persistWithContext(context: Context, displayMode: RoomListDisplayMode) {
+        val sp = getSharedPreferences(context)
+        val pref = getRoomListExpandedLowPriorityPref(displayMode)
+        sp.edit().putBoolean(pref, isLowPriorityRoomsExpanded).apply()
+    }
+
     fun isCategoryExpanded(roomCategory: RoomCategory): Boolean {
         return when (roomCategory) {
             RoomCategory.INVITE        -> isInviteExpanded