Flutter onTap stopped working and null error

user_16840728 0
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i'm getting null error in flutter button stopped working after added if statement inside the ontap here is my flutter code error Another exception was thrown: NoSuchMethodError: '<Unexpected Null Value>'
here is my button code

import 'package:efood_multivendor/controller/product_controller.dart';
import 'package:efood_multivendor/util/dimensions.dart';
import 'package:flutter/material.dart';
import 'package:get/get_core/src/get_main.dart';
import 'package:get/get_instance/src/extension_instance.dart';
import 'package:get/get_utils/src/extensions/internacionalization.dart';

import 'custom_snackbar.dart';

class QuantityButton extends StatelessWidget {
  final bool isIncrement;
  final Function onTap;
  final int quantity;
  final int stock;
  QuantityButton(
      {@required this.isIncrement,
      @required this.onTap,
      @required this.quantity,
      @required this.stock});

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: onTap({
      if(quantity < stock) {
      Get.find()<ProductController>(context, listen: false).setQuantity(true);
      } else {
      showCustomSnackBar('out_of_stock'.tr);
      }

      }),
      child: Container(
        height: 22,
        width: 22,
        margin: EdgeInsets.symmetric(horizontal: Dimensions.PADDING_SIZE_SMALL),
        decoration: BoxDecoration(
          shape: BoxShape.circle,
          border: Border.all(
              width: 1,
              color: isIncrement
                  ? Theme.of(context).primaryColor
                  : Theme.of(context).disabledColor),
          color: isIncrement
              ? Theme.of(context).primaryColor
              : Theme.of(context).disabledColor.withOpacity(0.2),
       
        ),
      ),
    );
  }
}

please help me o solve this problem without removing onTap : onTap function

flutter-dependencies flutter-web flutter-layout flutter android-studio
1 Answers

The error is originating from the value you are providing to the onTap parameter of the InkwWell widget, the onTap parameter is expecting a {void Function()?} and what you are providing is not the right type. What you are doing is calling the onTap of the widget with a parameter of type Set, instead of providing the function itself. The solution would be either to pass widget's onTap directly to the InkWell onTap like this

InkWell(
      onTap: onTap,

or if you wanna call the onTap with parameters you can use a lambda function like this :

InkWell(
      onTap: () => onTap(param1: value1, param2: value2),

These two solutions should work but what I see here, is that you are trying to define a logic when calling the onTap, which is not correct. the widget's onTap logic should be defined when creating the QuantityButton class like the following :

QuantityButton(
  onTap : () {
    if(quantity < stock) {
      Get.find()<ProductController>(context, listen: false).setQuantity(true);
     } else {
      showCustomSnackBar('out_of_stock'.tr);
      }
  }, rest of the parameters...);
user_89292990
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