init static method
Implementation
static Future init({bool initScheduled = false}) async {
const android = AndroidInitializationSettings('@mipmap/ic_launcher');
const iOS = IOSInitializationSettings();
const settings = InitializationSettings(android: android, iOS: iOS);
await _flutterLocalNotifications.initialize(settings,
onSelectNotification: (payload) {
onNotification.add(payload);
});
}