像这样使用permision_handler包：

Future<void> requestNotificationPermissions() async {
   final PermissionStatus status = await Permission.notification.request();
   if (status.isGranted) {
      // Notification permissions granted
   } else if (status.isDenied) {
      // Notification permissions denied
   } else if (status.isPermanentlyDenied) {
      // Notification permissions permanently denied, open app settings
      await openAppSettings();
   }
}