toMap method Null safety

Implementation

Map<String, dynamic> toMap() {
  HashMap<String, dynamic> dic = HashMap.of({
    'uid': uid,
    'roomId': roomId,
    'x': x,
    'y': y,
    'w': w,
    'h': h,
    'zorder': zorder,
    'alpha': alpha,
    'contentControl': contentControl.value,
    'renderMode': renderMode.value,
    'localUser': localUser,
    'isScreen': isScreen,
    'type': type.value,
  });
  if (this.data != null) {
    dic['data'] = data;
  }
  if (this.dataParam != null) {
    dic['dataParam'] = dataParam?.toMap();
  }
  return dic;
}