code: @Override public void showTraces(List<Trace> traces, int removedTraces) {
      if (lastScrollPosition == 0) {
        lastScrollPosition = lv_traces.getFirstVisiblePosition();
      }
      adapter.clear();
      adapter.addAll(traces);
      adapter.notifyDataSetChanged();
      updateScrollPosition(removedTraces);
    }
docs: Given a {@code List<Trace>} updates the ListView adapter with this information and keeps the
  scroll position if needed.