Crash when compiling null, at character offset null - Flutter and Dart

Question

I'm new to flutter and dart and I am trying to make a clone of instagram for studying purposes, but I am getting the error below.

Could you help me identify where the code is incorrect?

The output message error is in the end.

I tried google, and refactor the code ir order to apply the Null Safe, but in reality I don't know where exactly is the wrong code.

main.dart

import 'package:flutter/material.dart';
import 'package:instagram_flutter/responsive/mobile_screen_layout.dart';
import 'package:instagram_flutter/responsive/responsive_layout_screen.dart';
import 'package:instagram_flutter/responsive/web_screen_layout.dart';
import 'package:instagram_flutter/utils/colors.dart';

void main() {
  runApp(const MyApp());
}

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Instagram Clone',
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: mobileBackgroundColor,
      ),
      home: ResponsiveLayout(
        webScreenLayout: WebScreenLayout(),
        mobileScreenLayout: MobileScreenLayout(),
      ),
    );
  }
}

mobile_screen_layout.dart

import 'package:flutter/material.dart';

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Text('This is mobile'),
      ),
    );
  }
}

responsive_layout_screen.dart

In the IF ELSE below, i tried put a verification in some ways, to verify is the value is zero or null, but didn't work. I also tried to put ? in the end of contrainsts.maxWidth because I saw in my researchs that this avoids the null value, but didn't work either.

import 'package:flutter/material.dart';
import 'package:instagram_flutter/responsive/web_screen_layout.dart';
import 'package:instagram_flutter/utils/dimensions.dart';

class ResponsiveLayout extends StatelessWidget {
  final Widget webScreenLayout;
  final Widget mobileScreenLayout;

  const ResponsiveLayout({
    super.key,
    required this.webScreenLayout,
    required this.mobileScreenLayout,
  });

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(
      builder: (context, constraints) {
        if (constraints.maxWidth > webScreenSize) {
          return webScreenLayout;
        }
        return mobileScreenLayout;
      },
    );
  }
}

web_screen_layout.dart

import 'package:flutter/material.dart';

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Text('This is web'),
      ),
    );
  }
}

colors.dart

import 'package:flutter/material.dart';

const mobileBackgroundColor = Color.fromRGBO(0, 0, 0, 1);
const webBackgroundColor = Color.fromRGBO(18, 18, 18, 1);
const mobileSearchColor = Color.fromRGBO(38, 38, 38, 1);
const blueColor = Color.fromRGBO(0, 149, 246, 1);
const primaryColor = Colors.white;
const secondaryColor = Colors.grey;

dimensions.dart

import 'package:flutter/material.dart';
import 'package:instagram_flutter/responsive/web_screen_layout.dart';

const webScreenSize = 600;

OUTPUT

[Running] dart "c:\Development\instagram_flutter\lib\main.dart"
Crash when compiling null,
at character offset null:
Null check operator used on a null value
#0      InferableTypeBuilderMixin.type (package:front_end/src/fasta/builder/type_builder.dart:392:29)
#1      InferableTypeBuilder.inferType (package:front_end/src/fasta/builder/omitted_type_builder.dart:155:12)
#2      SourceLoader.performTopLevelInference (package:front_end/src/fasta/source/source_loader.dart:2358:19)
#3      KernelTarget.buildOutlines.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:532:14)
<asynchronous suspension>
#4      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#5      _buildInternal (package:front_end/src/kernel_generator_impl.dart:139:7)
<asynchronous suspension>
#6      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#7      generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#8      generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#9      kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#10     SingleShotCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:412:11)
<asynchronous suspension>
#11     Compiler.compile.<anonymous closure> (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:221:45)
<asynchronous suspension>
#12     _processLoadRequest (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:914:37)
<asynchronous suspension>


#0      InferableTypeBuilderMixin.type (package:front_end/src/fasta/builder/type_builder.dart:392:29)
#1      InferableTypeBuilder.inferType (package:front_end/src/fasta/builder/omitted_type_builder.dart:155:12)
#2      SourceLoader.performTopLevelInference (package:front_end/src/fasta/source/source_loader.dart:2358:19)
#3      KernelTarget.buildOutlines.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:532:14)
<asynchronous suspension>
#4      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#5      _buildInternal (package:front_end/src/kernel_generator_impl.dart:139:7)
<asynchronous suspension>
#6      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#7      generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#8      generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#9      kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#10     SingleShotCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:412:11)
<asynchronous suspension>
#11     Compiler.compile.<anonymous closure> (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:221:45)
<asynchronous suspension>
#12     _processLoadRequest (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:914:37)
<asynchronous suspension>


[Done] exited with code=252 in 5.039 seconds

you;ve pasted same data on `dimensions` as color – Md. Yeasin Sheikh Jul 21 '22 at 20:59 — Md. Yeasin Sheikh, Jul 21 '22 at 20:59
@YeasinSheikh sorry, already corrected. – KaioMartins Jul 21 '22 at 21:06 — KaioMartins, Jul 21 '22 at 21:06
try below answer and let me know if it solves the issue – Md. Yeasin Sheikh Jul 21 '22 at 21:08 — Md. Yeasin Sheikh, Jul 21 '22 at 21:08
I think there is `!` sign was used on `null` variable. – Miftakhul Arzak Jul 22 '22 at 06:33 — Miftakhul Arzak, Jul 22 '22 at 06:33

Akar Jaza · Answer 1 · 2022-09-16T18:04:30.990

2

After 3 days of searching I was able to fix the problem, just through deleting this Extension, if you don't have this extension but the problem persists, then the problem is definitely one extension, try disabling it one by one and reload vscode until you find it

edited Sep 16 '22 at 18:04

answered Sep 16 '22 at 17:39

Akar Jaza

61
7

score 0 · Answer 2 · answered Jul 21 '22 at 21:04

0

The issue is from ResponsiveLayout

if (constraints.maxWidth > webScreenSize?) { //here
  return webScreenLayout;
}

remove ? and do like

if (constraints.maxWidth > webScreenSize) {  
  return webScreenLayout;
}

answered Jul 21 '22 at 21:04

Md. Yeasin Sheikh

54,221
7
29
56

Same error. Updated the code. – KaioMartins Jul 21 '22 at 21:10
Can you try `flutter clean` and rebuild the app – Md. Yeasin Sheikh Jul 21 '22 at 21:12
I executed the following commands, same error flutter clean flutter packages get flutter upgrade – KaioMartins Jul 21 '22 at 21:17

score 0 · Answer 3 · answered Oct 08 '22 at 09:49

0

Disable coderunner extension and run flutter upgrade and also if is it doesn't work, run flutter clean and then flutter pub get in terminal, it works for me hope for you too

answered Oct 08 '22 at 09:49

Pratham Gangwal

1

score 0 · Answer 4 · answered Nov 23 '22 at 10:33

0

Disable coderunner extension and restart your workspace/vs code. It works for me hope for you too.

answered Nov 23 '22 at 10:33

20CEB061_Chirag Singhal

1
1

Crash when compiling null, at character offset null - Flutter and Dart

4 Answers4