- ValueGetter<
Future< bool>> callback
Register the callback to be called when the object changes.
If other callbacks have already been registered, they must be removed (with removeCallback) before the callback is next called.
Implementation
@override
void addCallback(ValueGetter<Future<bool>> callback) {
if (!hasCallbacks) {
WidgetsBinding.instance.addObserver(this);
}
super.addCallback(callback);
}