notifyNewMessageComing method
New message first key
When reach new message, the count will be disppear
For example if new message {id: 1},{id:2},{id:3}
, the key should be 1
if hasPrevMsgs
is true, widget can calc the count, we need simple increase newMsgCount
Implementation
notifyNewMessageComing(String firstKey, int newMsgCount) {
_handleNewMessageComing(firstKey, newMsgCount);
}