Minor collapsible group changes

app/src/main/java/com/todoroo/astrid/activity/TaskListFragment.kt

@@ -239,7 +239,7 @@ class TaskListFragment : InjectingFragment(), OnRefreshListener, Toolbar.OnMenuI
         } else if (recyclerAdapter !is DragAndDropRecyclerAdapter) {
             setAdapter(
                     DragAndDropRecyclerAdapter(
-                            taskAdapter, recyclerView, viewHolderFactory, this, tasks as MutableList, taskDao, preferences))
+                            taskAdapter, recyclerView, viewHolderFactory, this, tasks, taskDao, preferences))
             return
         }
         recyclerAdapter!!.submitList(tasks)

app/src/main/java/com/todoroo/astrid/adapter/TaskAdapter.kt

@@ -8,6 +8,7 @@ package com.todoroo.astrid.adapter
 import com.todoroo.astrid.data.Task
 import org.tasks.data.TaskContainer
 import java.util.*
+import kotlin.collections.HashSet
 
 open class TaskAdapter {
     private val selected = HashSet<Long>()
@@ -33,7 +34,7 @@ open class TaskAdapter {
 
     fun clearSelections() = selected.clear()
 
-    fun getCollapsed(): ArrayList<Long> = ArrayList(collapsed)
+    fun getCollapsed(): MutableSet<Long> = HashSet(collapsed)
 
     fun setCollapsed(groups: LongArray?) {
         clearCollapsed()

app/src/main/java/org/tasks/tasklist/DragAndDropRecyclerAdapter.kt

@@ -28,7 +28,7 @@ class DragAndDropRecyclerAdapter(
         private val recyclerView: RecyclerView,
         viewHolderFactory: ViewHolderFactory,
         private val taskList: TaskListFragment,
-        tasks: MutableList<TaskContainer>,
+        tasks: List<TaskContainer>,
         taskDao: TaskDao,
         preferences: Preferences) : TaskListRecyclerAdapter(adapter, viewHolderFactory, taskList, taskDao, preferences) {
     private var list: SectionedDataSource
@@ -69,7 +69,7 @@ class DragAndDropRecyclerAdapter(
 
     override fun submitList(list: List<TaskContainer>) {
         disposables.add(
-                Single.fromCallable { SectionedDataSource(list as MutableList, disableHeaders, preferences.sortMode, adapter.getCollapsed().toMutableSet()) }
+                Single.fromCallable { SectionedDataSource(list, disableHeaders, preferences.sortMode, adapter.getCollapsed()) }
                         .subscribeOn(Schedulers.computation())
                         .subscribe(publishSubject::onNext))
     }