The TypedEventNotifier library allows notifying listeners with an object.
listeners can be subscribed to only a special type or group of objects.
Installation
Add on pubspec.yml:
dependencies:
typed_event_notifier: ... // latest package version
Usage
See example in /example folder
import 'package:typed_event_notifier/typed_event_notifier.dart';
/// Class [ExampleNotifier].
///
/// The example of notifier.
/// It can send notifications to listeners with an object
/// and notify listeners if they are registered for this object type
/// or extended objects.
class ExampleNotifier extends TypedEventNotifier<Event> {
/// Create [ExampleNotifier] instance.
ExampleNotifier();
/// Will notify listeners with [CurrentPageChangedEvent] event.
void currentPage(int index) {
_currentPage = index;
notifyListeners(CurrentPageChangedEvent(currentPage: currentPage));
}
/// Will notify listeners with [PagesLoadedEvent] event.
set loadedPages(Set<int> set) {
_loadedPages.addAll(set);
notifyListeners(PagesLoadedEvent(pages: set));
}
}
//The part of example of listener on `current page changed` event only.
class _CurrentPageOnlyListenerState extends State<CurrentPageOnlyListener> {
String message = 'CurrentPageOnly: empty';
// Will receive events only with CurrentPageChangedEvent type.
void currentPageChanged(CurrentPageChangedEvent event) {
setState(() {
message = 'CurrentPageOnly: now current page is ${event.currentPage}';
});
}
@override
void initState() {
widget.notifier.addListener(currentPageChanged);
super.initState();
}
@override
void dispose() {
widget.notifier.removeListener(currentPageChanged);
super.dispose();
}
@override
Widget build(BuildContext context) {
return Text(message);
}
}
// The part of example of listener on any event.
class _AnyListenerState extends State<AnyListener> {
String message = 'Any: empty';
// Will receive events with CurrentPageChangedEvent and PagesLoadedEvent type.
void any(Event event) {
if (event is CurrentPageChangedEvent) {
setState(() {
message = 'Any: now current page is ${event.currentPage}';
});
}
if (event is PagesLoadedEvent) {
setState(() {
message = 'Any: new loaded pages is ${event.pages}';
});
}
}
@override
void initState() {
widget.notifier.addListener(any);
super.initState();
}
@override
void dispose() {
widget.notifier.removeListener(any);
super.dispose();
}
@override
Widget build(BuildContext context) {
return Text(message);
}
}
// The events for example, which will be sent through the notifier.
// They have abstract base class (used as parent type),
// and extends from it events.
// for example two types with different content.
/// Class [Event].
abstract class Event {
/// Create [Event] instance.
Event();
}
/// Class [CurrentPageChangedEvent].
class CurrentPageChangedEvent extends Event {
/// Index of current page.
final int currentPage;
/// Create [CurrentPageChangedEvent] instance.
CurrentPageChangedEvent({
required this.currentPage,
}) : super();
}
/// Class [PagesLoadedEvent].
class PagesLoadedEvent extends Event {
/// Indexes of loaded pages.
final Set<int> pages;
/// Create [PagesLoadedEvent] instance.
PagesLoadedEvent({
required this.pages,
}) : super();
}
