main.dart

 void initListeners() {
    billingHelper?.setPurchaseUpdateHandler((status, value) async {
      switch (status) {
        case 'success':
          if (kDebugMode) {
            print('$status : $value');
            ScaffoldMessenger.of(context).showSnackBar(SnackBar(
                duration: const Duration(seconds: 1),
                backgroundColor: Utils.getPrimaryColor(),
                content: Text(
                  'Purchase Sucessfully',
                  style: TextStyle(fontSize: 18.0, fontFamily: 'Sans', fontStyle: FontStyle.normal, fontWeight: FontWeight.w500, color: Utils.getWhiteColor()),
                )));
          }
          break;
        case 'cancelled':
          if (kDebugMode) {
            print('$status : $value');
            ScaffoldMessenger.of(context).showSnackBar(SnackBar(
                duration: const Duration(seconds: 1),
                backgroundColor: Utils.getPrimaryColor(),
                content: Text(
                  'Purchase cancelled by you',
                  style: TextStyle(fontSize: 18.0, fontFamily: 'Sans', fontStyle: FontStyle.normal, fontWeight: FontWeight.w500, color: Utils.getWhiteColor()),
                )));
          }
          break;
        case 'error':
          if (kDebugMode) {
            print('$status : $value');
            ScaffoldMessenger.of(context).showSnackBar(SnackBar(
                duration: const Duration(seconds: 1),
                backgroundColor: Utils.getPrimaryColor(),
                content: Text(
                  'Something went wrong, Please try again after sometime',
                  style: TextStyle(fontSize: 18.0, fontFamily: 'Sans', fontStyle: FontStyle.normal, fontWeight: FontWeight.w500, color: Utils.getWhiteColor()),
                )));
          }
          break;
        case 'restore':
          if (kDebugMode) {
            print('$status : $value');
            ScaffoldMessenger.of(context).showSnackBar(SnackBar(
                duration: const Duration(seconds: 1),
                backgroundColor: Utils.getPrimaryColor(),
                content: Text(
                  value ? 'Restore Successfully' : 'You don\'t have purchase to restore',
                  style: TextStyle(fontSize: 18.0, fontFamily: 'Sans', fontStyle: FontStyle.normal, fontWeight: FontWeight.w500, color: Utils.getWhiteColor()),
                )));
          }
          break;
        default:
          if (kDebugMode) {
            print('$status : $value');
          }
      }
    });

    billingHelper!.setPriceUpdateHandler((price) {
      if (kDebugMode) {
        print("Price: $price");
        setState(() {
          this.price = price;
        });
      }
    });
  }