nulled error in android studio ontap function

Question

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/src/widgets/container.dart';
import 'package:flutter/src/widgets/framework.dart';
import 'package:safehandsv2/utils/quotes.dart';

class CustomAppBar extends StatelessWidget {
  //const CustomAppBar({super.key});

  Function? onTap;
  int? quoteIndex;
  CustomAppBar({this.onTap, this.quoteIndex});


  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap:() {
        **onTap!();**
      },
      child: Text(sweetSayings[quoteIndex!],
      
      style: TextStyle(fontSize: 22, ),
      
      ),

      
    );
  }
}

so here the error I'm getting is null not defined etc.

error - Exception has occurred.
_CastError (Null check operator used on a null value)

MendelG · Answer 1 · 2022-12-29T06:52:17.457

Your function onTap is defined as nullable (the ?):

Function? onTap;

then, you're calling the function using the ! operator, which means to say "I won't be null" but when you called it, it was indeed null.

So, first, check if it's null before calling it:

onTap: () {
        if (onTap != null) {
          onTap!();
        }
      },

When your calling CustomAppBar you're probably not passing in an onTap, since it's optional.

nulled error in android studio ontap function

1 Answers1

See also