public class messaging extends FirebaseMessagingService {

   @Override
   public void onMessageReceived(RemoteMessage m) {
      store(m.getData());
      broadcastIntent();
   }

   public void broadcastIntent() {
      Intent intent = new Intent();
      intent.setAction("com.myApp.CUSTOM_EVENT");
      sendBroadcast(intent);
   }
}

public class ConvoAdapter extends RecyclerView.Adapter<ConvoHolder> {

   private List<Message> list;
   private Activity      A;

   public ConvoAdapter(List<Message> data) {

   }

   @Override
   public ConvoHolder onCreateViewHolder(ViewGroup parent, int viewType) {
      View v = LayoutInflater.from(parent.getContext()).inflate(layout, parent, false);
      return new ConvoHolder(v);
   }

   @Override
   public void onBindViewHolder(ConvoHolder h, int Position) {
      final Message M = list.get(Position);
      h.config(A, M);
   }

    @Override
    public int getItemCount() {
       return list.size();
    }

    public class MyReceiver extends BroadcastReceiver {
          @Override
          public void onReceive(Context context, Intent intent) {
             Toast.makeText(context, "Intent Detected.",    Toast.LENGTH_LONG).show();
          }
    }
}

<receiver android:name=".fragments.chats.ConvoAdapter$MyReceiver"
                  android:enabled="true"
                  android:exported="false" >
            <intent-filter>
                <action android:name="android.intent.action.CUSTOM_EVENT">
                </action>
            </intent-filter>
        </receiver>

public class messaging extends FirebaseMessagingService {

   @Override
   public void onMessageReceived(RemoteMessage m) {
      store(m.getData());
      broadcastIntent();
   }

  public void broadcastIntent() {
      Intent intent = new Intent();
      intent.setAction("com.myApp.CUSTOM_EVENT");
      // We should use LocalBroadcastManager when we want INTRA app
      // communication
      LocalBroadcastManager.getInstance(YOUR_CONTEXT).sendBroadcast(intent);
  }
}

public void onCreate(Bundle savedInstance) {
       // REST OF YOUR CODE
       IntentFilter if= new IntentFilter("com.myApp.CUSTOM_EVENT");
       LocalBroadcastManager.getInstance(this).registerReceiver(onMessage, if);
  }

private BroadcastReceiver onNotice= new BroadcastReceiver() {
      @Override
      public void onReceive(Context context, Intent intent) {
             // Update your RecyclerView here using notifyItemInserted(position);
      }};

<action android:name="com.myApp.CUSTOM_EVENT">
                </action>

intent.setAction("com.myApp.CUSTOM_EVENT");