addValueListener method
Implementation
@override
void addValueListener(ValueCallback<T> listener) {
_initializeMixinVariables();
assert(null != _valueListeners && null != _valueListenersCount);
if (0 == _valueListenersCount) {
_valueListeners = List<ValueCallback<T>?>.filled(1, listener);
_valueListenersCount = 1;
return;
}
// Increase size of _valueListeners.
if (_valueListenersCount! >= _valueListeners!.length) {
final newListeners =
List<ValueCallback<T>?>.filled(_valueListeners!.length * 2, null);
for (var i = 0; i < _valueListenersCount!; i++)
newListeners[i] = _valueListeners![i];
_valueListeners = newListeners;
}
_valueListeners![_valueListenersCount!] = listener;
_valueListenersCount = _valueListenersCount! + 1;
}