addMessage method
Implementation
@override
void addMessage(MessageModel message) {
//fix Bad state: Cannot add event after closing
if (messageStreamController.isClosed) return;
inflateMessage(message);
//List反转后列是从底部向上展示,所以新来的消息需要插入到数据第0个位置
initialMessageList.insert(0, message);
messageStreamController.sink.add(initialMessageList);
scrollToLastMessage();
}