List<Track> tracks = getTracks();
trackGroups.clear();
if (attribute == null || attribute.length() == 0) {
TrackGroup nullGroup = new TrackGroup();
nullGroup.addAll(tracks);
nullGroup.setDrawBorder(false);
trackGroups.add(nullGroup);
} else {
Map<String, TrackGroup> groupMap = new HashMap();
for (Track track : tracks) {