addListener method
Register a closure to be called when the object notifies its listeners.
Implementation
@override
void addListener(VoidCallback listener) {
assert(!_listeners.contains(listener));
_listeners.add(listener);
}
Register a closure to be called when the object notifies its listeners.
@override
void addListener(VoidCallback listener) {
assert(!_listeners.contains(listener));
_listeners.add(listener);
}