list should remember its state

app/src/main/java/org/y20k/escapepod/Keys.kt

@@ -52,6 +52,7 @@ object Keys {
 
     // keys
     const val KEY_DOWNLOAD_WORK_REQUEST: String = "DOWNLOAD_WORK_REQUEST"
+    const val KEY_SAVE_INSTANCE_STATE_PODCAST_LIST: String = "SAVE_INSTANCE_STATE_PODCAST_LIST"
 
     // custom MediaController commands
     const val CMD_RELOAD_PLAYER_STATE: String = "RELOAD_PLAYER_STATE"

app/src/main/java/org/y20k/escapepod/PodcastPlayerActivity.kt

@@ -80,6 +80,7 @@ class PodcastPlayerActivity: AppCompatActivity(), CoroutineScope,
     private var playerServiceConnected: Boolean = false
     private var onboarding: Boolean = false
     private var playerState: PlayerState = PlayerState()
+    private var listLayoutState: Parcelable? = null
     private var opmlCreatedObserver: FileObserver? = null
     private var tempOpmlUriString: String = String()
     private val handler: Handler = Handler()
@@ -125,15 +126,35 @@ class PodcastPlayerActivity: AppCompatActivity(), CoroutineScope,
     }
 
 
+    /* Overrides onSaveInstanceState */
+    override fun onSaveInstanceState(outState: Bundle) {
+        // save current state of podcast list
+        listLayoutState = layout.layoutManager.onSaveInstanceState()
+        outState.putParcelable(Keys.KEY_SAVE_INSTANCE_STATE_PODCAST_LIST, listLayoutState)
+        // always call the superclass so it can save the view hierarchy state
+        super.onSaveInstanceState(outState)
+    }
+
+
+    /* Overrides onRestoreInstanceState */
+    override fun onRestoreInstanceState(savedInstanceState: Bundle) {
+        // always call the superclass so it can restore the view hierarchy
+        super.onRestoreInstanceState(savedInstanceState)
+        // restore state of podcast list
+        listLayoutState = savedInstanceState.getParcelable(Keys.KEY_SAVE_INSTANCE_STATE_PODCAST_LIST)
+    }
+
+
     /* Overrides onResume */
     override fun onResume() {
         super.onResume()
         // assign volume buttons to music volume
         volumeControlStream = AudioManager.STREAM_MUSIC
         // try to recreate player state
         playerState = PreferencesHelper.loadPlayerState(this)
-        // setup player ui
+        // setup ui
         setupPlayer()
+        setupList()
         // start watching for changes in shared preferences
         PreferencesHelper.registerPreferenceChangeListener(this)
         // toggle download progress indicator
@@ -535,7 +556,7 @@ class PodcastPlayerActivity: AppCompatActivity(), CoroutineScope,
     private fun setupPlayer() {
         // toggle player visibility
         if (layout.togglePlayerVisibility(this, playerState.playbackState)) {
-            // CASE: player is visible
+            // CASE: player is visible - update player views
             layout.togglePlayButtons(playerState.playbackState)
             if (playerState.episodeMediaId.isNotEmpty()) {
                 val episode: Episode = CollectionHelper.getEpisode(collection, playerState.episodeMediaId)
@@ -547,6 +568,14 @@ class PodcastPlayerActivity: AppCompatActivity(), CoroutineScope,
     }
 
 
+    /* Sets up state of list podcast list */
+    private fun setupList() {
+        if (listLayoutState != null) {
+            layout.layoutManager.onRestoreInstanceState(listLayoutState)
+        }
+    }
+
+
     /* Starts / pauses playback */
     private fun togglePlayback(startPlayback: Boolean, mediaId: String, playbackState: Int) {
         playerState.episodeMediaId = mediaId

app/src/main/java/org/y20k/escapepod/ui/LayoutHolder.kt

@@ -17,6 +17,7 @@ package org.y20k.escapepod.ui
 import android.app.Activity
 import android.content.Context
 import android.net.Uri
+import android.os.Parcelable
 import android.os.Vibrator
 import android.support.v4.media.session.PlaybackStateCompat
 import android.view.View
@@ -55,6 +56,7 @@ data class LayoutHolder(var activity: Activity) {
     /* Main class variables */
     var swipeRefreshLayout: SwipeRefreshLayout
     var recyclerView: RecyclerView
+    val layoutManager: LinearLayoutManager
     private var bottomSheet: ConstraintLayout
     private var playerViews: Group
     private var upNextViews: Group
@@ -120,9 +122,12 @@ data class LayoutHolder(var activity: Activity) {
         bottomSheetBehavior = BottomSheetBehavior.from(bottomSheet)
         displayTimeRemaining = false
 
+        // set up RecyclerView
+        layoutManager = CustomLayoutManager(activity)
+        recyclerView.layoutManager = layoutManager
+        recyclerView.itemAnimator = DefaultItemAnimator()
 
-        // set layouts for list and player
-        setupRecyclerView()
+        // set layout for player
         setupBottomSheet()
     }
 
@@ -340,19 +345,6 @@ data class LayoutHolder(var activity: Activity) {
     }
 
 
-
-    /* Sets up list of podcasts (RecyclerView) */
-    private fun setupRecyclerView() {
-        val layoutManager: LinearLayoutManager = object: LinearLayoutManager(activity) {
-            override fun supportsPredictiveItemAnimations(): Boolean {
-                return true
-            }
-        }
-        recyclerView.layoutManager = layoutManager
-        recyclerView.itemAnimator = DefaultItemAnimator()
-    }
-
-
     /* Sets up the player (BottomSheet) */
     private fun setupBottomSheet() {
         // show / hide the small player
@@ -406,4 +398,26 @@ data class LayoutHolder(var activity: Activity) {
         }
     }
 
+
+    /*
+     * Inner class: custom LinearLayoutManager
+     */
+    private inner class CustomLayoutManager(context: Context): LinearLayoutManager(context, VERTICAL, false) {
+        var listState: Parcelable? = null
+        override fun supportsPredictiveItemAnimations(): Boolean {
+            return true
+        }
+//        override fun onLayoutCompleted(state: RecyclerView.State?) {
+//            if (state == null) scrollToPosition(0)
+//        }
+//        override fun onRestoreInstanceState(state: Parcelable?) {
+//            listState = state
+//            super.onRestoreInstanceState(state)
+//        }
+    }
+    /*
+     * End of inner class
+     */
+
+
 }