setMessageStatusCallBack method Null safety

void setMessageStatusCallBack(
  1. MessageStatusCallBack? callback
)

Implementation

void setMessageStatusCallBack(MessageStatusCallBack? callback) {
  _messageStatusCallBack = callback;
  if (callback != null) {
    MessageCallBackManager.getInstance.addMessage(this);
  } else {
    MessageCallBackManager.getInstance.removeMessage(localTime.toString());
  }
}