Revert "Revert "Won't disrupt message reading""

This reverts commit ae5211eb.

app/src/main/java/chat/rocket/android/fragment/chatroom/RoomFragment.java

@@ -28,6 +28,7 @@ import chat.rocket.android.helper.LoadMoreScrollListener;
 import chat.rocket.android.helper.LogcatIfError;
 import chat.rocket.android.helper.OnBackPressListener;
 import chat.rocket.android.helper.TextUtils;
+import chat.rocket.android.layouthelper.ExtRealmModelListAdapter;
 import chat.rocket.android.layouthelper.chatroom.MessageFormManager;
 import chat.rocket.android.layouthelper.chatroom.MessageListAdapter;
 import chat.rocket.android.layouthelper.chatroom.PairedMessage;
@@ -70,6 +71,17 @@ public class RoomFragment extends AbstractChatRoomFragment
   private LoadMoreScrollListener scrollListener;
   private RealmObjectObserver<LoadMessageProcedure> procedureObserver;
   private MessageFormManager messageFormManager;
+  private LinearLayoutManager layoutManager;
+  private boolean userScrolledToEnd = true;
+
+  private ExtRealmModelListAdapter.UpdateListener updateListener =
+      count -> {
+        if (userScrolledToEnd) {
+          scrollToEnd();
+        } else {
+          // showNewMessagesAtEndIndicator();
+        }
+      };
 
   public RoomFragment() {
   }
@@ -142,9 +154,10 @@ public class RoomFragment extends AbstractChatRoomFragment
     listView.setAdapter(adapter);
     adapter.setOnItemClickListener(this);
 
-    LinearLayoutManager layoutManager = new LinearLayoutManager(getContext(),
+    layoutManager = new LinearLayoutManager(getContext(),
         LinearLayoutManager.VERTICAL, true);
     listView.setLayoutManager(layoutManager);
+    adapter.setUpdateListener(updateListener);
 
     scrollListener = new LoadMoreScrollListener(layoutManager, 40) {
       @Override
@@ -153,6 +166,13 @@ public class RoomFragment extends AbstractChatRoomFragment
       }
     };
     listView.addOnScrollListener(scrollListener);
+    listView.addOnScrollListener(new RecyclerView.OnScrollListener() {
+      @Override
+      public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
+        super.onScrollStateChanged(recyclerView, newState);
+        setUserScrolledToEnd(newState);
+      }
+    });
 
     setupSideMenu();
     setupMessageComposer();
@@ -372,4 +392,18 @@ public class RoomFragment extends AbstractChatRoomFragment
   protected void onExtraActionSelected(MessageExtraActionBehavior action) {
     action.handleItemSelectedOnFragment(RoomFragment.this);
   }
+
+  private void setUserScrolledToEnd(int newState) {
+    if (newState == RecyclerView.SCROLL_STATE_DRAGGING
+        || newState == RecyclerView.SCROLL_STATE_IDLE) {
+      userScrolledToEnd = layoutManager.findFirstCompletelyVisibleItemPosition() == 1;
+    }
+  }
+
+  private void scrollToEnd() {
+    if (layoutManager == null) {
+      return;
+    }
+    layoutManager.scrollToPosition(0);
+  }
 }

app/src/main/java/chat/rocket/android/layouthelper/ExtRealmModelListAdapter.java

@@ -17,6 +17,8 @@ public abstract class ExtRealmModelListAdapter<T extends RealmObject, VM,
   protected static final int VIEW_TYPE_HEADER = -1;
   protected static final int VIEW_TYPE_FOOTER = -2;
 
+  private UpdateListener updateListener;
+
   protected ExtRealmModelListAdapter(Context context) {
     super(context);
   }
@@ -38,10 +40,17 @@ public abstract class ExtRealmModelListAdapter<T extends RealmObject, VM,
     notifyItemChanged(position + 1);
   }
 
+  public void setUpdateListener(UpdateListener updateListener) {
+    this.updateListener = updateListener;
+  }
+
   protected ListUpdateCallback listUpdateCallback = new ListUpdateCallback() {
     @Override
     public void onInserted(int position, int count) {
       notifyItemRangeInserted(position + 1, count);
+      if (updateListener != null) {
+        updateListener.onInserted(count);
+      }
     }
 
     @Override
@@ -111,4 +120,10 @@ public abstract class ExtRealmModelListAdapter<T extends RealmObject, VM,
   public ListUpdateCallback getListUpdateCallback() {
     return listUpdateCallback;
   }
+
+  // We'll be using the insert event only as of now
+  // Let's add more events when/if needed
+  public interface UpdateListener {
+    void onInserted(int count);
+  }
 }