Using diff util to update the list

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

@@ -145,6 +145,7 @@ public class RoomFragment extends AbstractChatRoomFragment
     LinearLayoutManager layoutManager = new LinearLayoutManager(getContext(),
         LinearLayoutManager.VERTICAL, true);
     listView.setLayoutManager(layoutManager);
+    adapter.setLayoutManager(layoutManager);
 
     scrollListener = new LoadMoreScrollListener(layoutManager, 40) {
       @Override

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

@@ -2,6 +2,8 @@ package chat.rocket.android.layouthelper;
 
 import android.content.Context;
 import android.support.annotation.LayoutRes;
+import android.support.v7.util.ListUpdateCallback;
+import android.support.v7.widget.RecyclerView;
 import io.realm.RealmObject;
 
 import chat.rocket.android.realm_helper.RealmModelListAdapter;
@@ -16,6 +18,8 @@ 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 RecyclerView.LayoutManager layoutManager;
+
   protected ExtRealmModelListAdapter(Context context) {
     super(context);
   }
@@ -37,6 +41,35 @@ public abstract class ExtRealmModelListAdapter<T extends RealmObject, VM,
     notifyItemChanged(position + 1);
   }
 
+  public void setLayoutManager(RecyclerView.LayoutManager layoutManager) {
+    this.layoutManager = layoutManager;
+  }
+
+  protected ListUpdateCallback listUpdateCallback = new ListUpdateCallback() {
+    @Override
+    public void onInserted(int position, int count) {
+      notifyItemRangeInserted(position + 1, count);
+      if (layoutManager != null) {
+        layoutManager.scrollToPosition(0);
+      }
+    }
+
+    @Override
+    public void onRemoved(int position, int count) {
+      notifyItemRangeRemoved(position + 1, count);
+    }
+
+    @Override
+    public void onMoved(int fromPosition, int toPosition) {
+      notifyItemMoved(fromPosition + 1, toPosition + 1);
+    }
+
+    @Override
+    public void onChanged(int position, int count, Object payload) {
+      notifyItemRangeChanged(position + 1, count, payload);
+    }
+  };
+
   @Override
   public int getItemViewType(int position) {
     if (position == 0) {
@@ -83,4 +116,9 @@ public abstract class ExtRealmModelListAdapter<T extends RealmObject, VM,
     // rely on VH.bind().
     super.onBindViewHolder(holder, position - 1);
   }
+
+  @Override
+  public ListUpdateCallback getListUpdateCallback() {
+    return listUpdateCallback;
+  }
 }

app/src/main/java/chat/rocket/android/layouthelper/chatroom/MessageListAdapter.java

 package chat.rocket.android.layouthelper.chatroom;
 
 import android.content.Context;
+import android.support.v7.util.DiffUtil;
+import android.support.v7.widget.RecyclerView;
 import android.view.View;
 
 import java.util.ArrayList;
@@ -111,4 +113,53 @@ public class MessageListAdapter
 
     return extMessages;
   }
+
+  @Override
+  protected DiffUtil.Callback getDiffCallback(List<PairedMessage> oldData,
+                                              List<PairedMessage> newData) {
+    return new PairedMessageDiffCallback(oldData, newData);
+  }
+
+  private static class PairedMessageDiffCallback extends DiffUtil.Callback {
+
+    private final List<PairedMessage> oldList;
+    private final List<PairedMessage> newList;
+
+    public PairedMessageDiffCallback(List<PairedMessage> oldList, List<PairedMessage> newList) {
+      this.oldList = oldList;
+      this.newList = newList;
+    }
+
+    @Override
+    public int getOldListSize() {
+      if (oldList == null) {
+        return 0;
+      }
+      return oldList.size();
+    }
+
+    @Override
+    public int getNewListSize() {
+      if (newList == null) {
+        return 0;
+      }
+      return newList.size();
+    }
+
+    @Override
+    public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
+      PairedMessage oldMessage = oldList.get(oldItemPosition);
+      PairedMessage newMessage = newList.get(newItemPosition);
+
+      return oldMessage.getId().equals(newMessage.getId());
+    }
+
+    @Override
+    public boolean areContentsTheSame(int oldItemPosition, int newItemPosition) {
+      PairedMessage oldMessage = oldList.get(oldItemPosition);
+      PairedMessage newMessage = newList.get(newItemPosition);
+
+      return oldMessage.toString().equals(newMessage.toString());
+    }
+  }
 }

app/src/main/java/chat/rocket/android/layouthelper/chatroom/PairedMessage.java

@@ -32,4 +32,16 @@ public class PairedMessage {
         && nextSibling.getUser() != null && target.getUser() != null
         && nextSibling.getUser().getId().equals(target.getUser().getId());
   }
+
+  public String getId() {
+    return target.getId();
+  }
+
+  @Override
+  public String toString() {
+    return "PairedMessage{" +
+        "target=" + target +
+        ", nextSibling=" + nextSibling +
+        '}';
+  }
 }

app/src/main/java/chat/rocket/android/model/ddp/Message.java

@@ -131,4 +131,20 @@ public class Message extends RealmObject {
   public void setUrls(String urls) {
     this.urls = urls;
   }
+
+  @Override
+  public String toString() {
+    return "Message{" +
+        "_id='" + _id + '\'' +
+        ", t='" + t + '\'' +
+        ", rid='" + rid + '\'' +
+        ", syncstate=" + syncstate +
+        ", ts=" + ts +
+        ", msg='" + msg + '\'' +
+        ", u=" + u +
+        ", groupable=" + groupable +
+        ", attachments='" + attachments + '\'' +
+        ", urls='" + urls + '\'' +
+        '}';
+  }
 }

app/src/main/java/chat/rocket/android/model/ddp/User.java

@@ -79,4 +79,16 @@ public class User extends RealmObject {
   public Settings getSettings() {
     return settings;
   }
+
+  @Override
+  public String toString() {
+    return "User{" +
+        "_id='" + _id + '\'' +
+        ", username='" + username + '\'' +
+        ", status='" + status + '\'' +
+        ", utcOffset=" + utcOffset +
+        ", emails=" + emails +
+        ", settings=" + settings +
+        '}';
+  }
 }

realm-helpers/src/main/java/chat/rocket/android/realm_helper/RealmModelListAdapter.java

@@ -2,6 +2,8 @@ package chat.rocket.android.realm_helper;
 
 import android.content.Context;
 import android.support.annotation.LayoutRes;
+import android.support.v7.util.DiffUtil;
+import android.support.v7.util.ListUpdateCallback;
 import android.support.v7.widget.RecyclerView;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -89,12 +91,20 @@ public abstract class RealmModelListAdapter<T extends RealmObject, VM,
       adapterData = mapResultsToViewModel(newData);
       notifyDataSetChanged();
     } else {
-      // TODO: use DillUtils!
-      adapterData = mapResultsToViewModel(newData);
-      notifyDataSetChanged();
+      final List<VM> newMappedData = mapResultsToViewModel(newData);
+      final DiffUtil.Callback diffCallback = getDiffCallback(adapterData, newMappedData);
+      final DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(diffCallback);
+
+      adapterData = newMappedData;
+
+      diffResult.dispatchUpdatesTo(getListUpdateCallback());
     }
   }
 
+  protected abstract DiffUtil.Callback getDiffCallback(List<VM> oldData, List<VM> newData);
+
+  protected abstract ListUpdateCallback getListUpdateCallback();
+
   public void setOnItemClickListener(OnItemClickListener<VM> onItemClickListener) {
     this.onItemClickListener = onItemClickListener;
   }