implement "readMessages"

app/src/main/java/chat/rocket/android/api/MethodCallHelper.java

@@ -305,4 +305,12 @@ public class MethodCallHelper {
         .onSuccessTask(CONVERT_TO_JSON_OBJECT)
         .onSuccessTask(task -> Task.forResult(Message.customizeJson(task.getResult())));
   }
+
+  /**
+   * mark all messages are read in the room.
+   */
+  public Task<Void> readMessages(final String roomId) {
+    return call("readMessages", TIMEOUT_MS, () -> new JSONArray().put(roomId))
+        .onSuccessTask(task -> Task.forResult(null));
+  }
 }

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

@@ -11,6 +11,7 @@ import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
 import android.view.View;
 import chat.rocket.android.R;
+import chat.rocket.android.api.MethodCallHelper;
 import chat.rocket.android.fragment.chatroom.dialog.UsersOfRoomDialogFragment;
 import chat.rocket.android.helper.LoadMoreScrollListener;
 import chat.rocket.android.helper.LogcatIfError;
@@ -269,11 +270,21 @@ public class RoomFragment extends AbstractChatRoomFragment
     }).continueWith(new LogcatIfError());
   }
 
+  private void markAsReadIfNeeded() {
+    RoomSubscription room = realmHelper.executeTransactionForRead(realm ->
+        realm.where(RoomSubscription.class).equalTo("rid", roomId).findFirst());
+    if (room != null && room.isAlert()) {
+      new MethodCallHelper(getContext(), serverConfigId).readMessages(roomId)
+          .continueWith(new LogcatIfError());
+    }
+  }
+
   @Override public void onResume() {
     super.onResume();
     roomObserver.sub();
     procedureObserver.sub();
     closeSideMenuIfNeeded();
+    markAsReadIfNeeded();
   }
 
   @Override public void onPause() {