cancelListeners method
void
cancelListeners()
Cancel all listeners added.
It is fine to call this method and then add additional listeners.
Implementation
void cancelListeners() {
assert(_listenables.length == _listeners.length);
for (int i = 0; i < _listenables.length; ++i) {
_listenables[i].removeListener(_listeners[i]);
}
_listenables.clear();
_listeners.clear();
}