Flutter Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null

Question

Whenever I try to run flutter app, I am getting this error.

../flutter/.pub-cache/hosted/pub.dartlang.org/percent_indicator-4.2.1/lib/linear_percent_indicator.dart:162:5: Warning: The class 'WidgetsBinding' cannot be null.
Try replacing '?.' with '.'
    WidgetsBinding?.instance.addPostFrameCallback((_) {
    ^^^^^^^^^^^^^^
../flutter/.pub-cache/hosted/pub.dartlang.org/percent_indicator-4.2.1/lib/linear_percent_indicator.dart:162:30: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
    WidgetsBinding?.instance.addPostFrameCallback((_) {
                             ^^^^^^^^^^^^^^^^^^^^


FAILURE: Build failed with an exception.

* Where:
Script '/home/user/Downloads/flutter/packages/flutter_tools/gradle/flutter.gradle' line: 1102

* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command '/home/user/Downloads/flutter/bin/flutter'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 22s
Running Gradle task 'assembleDebug'...                             22.8s
Exception: Gradle task assembleDebug failed with exit code 1

Here, is my Flutter doctor output

[✓] Flutter (Channel stable, 2.10.3, on Ubuntu 20.04.4 LTS 5.13.0-41-generic, locale en_IN)
    • Flutter version 2.10.3 at /home/user/Downloads/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 7e9793dee1 (3 months ago), 2022-03-02 11:23:12 -0600
    • Engine revision bd539267b4
    • Dart version 2.16.1
    • DevTools version 2.9.2

[✓] Android toolchain - develop for Android devices (Android SDK version 32.1.0-rc1)
    • Android SDK at /home/user/Android/Sdk
    • Platform android-32, build-tools 32.1.0-rc1
    • Java binary at: /opt/android-studio-2021.1.1/android-studio/jre/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7590822)
    • All Android licenses accepted.

[✓] Chrome - develop for the web
    • Chrome at google-chrome

[✓] Android Studio (version 2021.1)
    • Android Studio at /opt/android-studio-2021.1.1/android-studio
    • Flutter plugin version 66.0.1
    • Dart plugin version 211.7811
    • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7590822)

[✓] Android Studio
    • Android Studio at /opt/android-studio
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.11+0-b60-7590822)

[✓] Connected device (2 available)
    • sdk gphone64 x86 64 (mobile) • emulator-5554 • android-x64    • Android 12 (API 31) (emulator)
    • Chrome (web)                 • chrome        • web-javascript • Google Chrome 99.0.4844.82

[✓] HTTP Host Availability
    • All required HTTP hosts are available

• No issues found!

I have tried following things already

Invalidate and restart android-studio
Deleted .gradle folder and try building again
flutter clean and then 'flutter pub get, flutter pub cache repair`
- also deleted build folder and pubspec.lock file

But nothing, worked

Also, here is my Gradle files

android/app/build.gradle

def localProperties = new Properties()
def localPropertiesFile = rootProject.file('local.properties')
if (localPropertiesFile.exists()) {
    localPropertiesFile.withReader('UTF-8') { reader ->
        localProperties.load(reader)
    }
}

def flutterRoot = localProperties.getProperty('flutter.sdk')
if (flutterRoot == null) {
    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
}

def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
if (flutterVersionCode == null) {
    flutterVersionCode = '1'
}

def flutterVersionName = localProperties.getProperty('flutter.versionName')
if (flutterVersionName == null) {
    flutterVersionName = '1.0'
}

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
apply plugin: 'com.google.gms.google-services'
android {
    compileSdkVersion flutter.compileSdkVersion

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    kotlinOptions {
        jvmTarget = '1.8'
    }

    sourceSets {
        main.java.srcDirs += 'src/main/kotlin'
    }
    splits {
        abi {
            enable true
            reset()
            include 'x86', 'armeabi-v7a'
            universalApk true
        }
    }
    defaultConfig {
        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
        applicationId "com.example.app.example"
        minSdkVersion 19
        targetSdkVersion flutter.targetSdkVersion
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
        multiDexEnabled = true
    }
    // signingConfigs {
    //     debug {
    //         if (debugKeystorePropertiesFile.exists()) {
    //             keyAlias debugKeystoreProperties['keyAlias']
    //             keyPassword debugKeystoreProperties['keyPassword']
    //             storeFile file(debugKeystoreProperties['storeFile'])
    //             storePassword debugKeystoreProperties['storePassword']
    //         }
    //     }
    // }
    buildTypes {
        release {
//            if (keystorePropertiesFile.exists()) {
//                signingConfig signingConfigs.release
//                println "Signing with key.properties"
//            } else {
                signingConfig signingConfigs.debug
                println "Signing with debug keys"
//            }
        }
    }
}

flutter {
    source '../..'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation platform('com.google.firebase:firebase-bom:29.2.1')
    implementation 'com.google.firebase:firebase-auth-ktx'
    implementation 'com.google.android.gms:play-services-safetynet:18.0.1'
    implementation 'com.google.firebase:firebase-appcheck-safetynet:16.0.0-beta05'

    implementation "androidx.browser:browser:1.3.0"
}

android/build.gradle

buildscript {
    ext.kotlin_version = '1.6.10'
    repositories {
        google()
        mavenCentral()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:4.1.0'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
        classpath 'com.google.gms:google-services:4.3.10'
    }
}

allprojects {
    repositories {
        google()
        mavenCentral()
    }
}

rootProject.buildDir = '../build'
subprojects {
    project.buildDir = "${rootProject.buildDir}/${project.name}"
}
subprojects {
    project.evaluationDependsOn(':app')
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

I do have added android.useAndroidX and android.enableJetifier to true
Also added android:exported="true" in androidmanifest.xml

This issue is caused by percent_indicator: ^4.0.0 I comment the usage of this lib and also removed from pubspec and it's working then. — Tushar Asodariya
– Tushar Asodariya, Commented May 16, 2022 at 8:49

CiganoSA · Accepted Answer · 2022-05-17 04:54:31Z

8

As @DiyorbekDev said, you should use the 4.0.1 version. 4.2.x is meant to Flutter 3 and have some null safety incompatibility issues.

You DO NOT need to add percent_indicator lib to local project. I've got through the same issue. I had to force pubspec.yaml to use the 4.0.1 version:

percent_indicator: 4.0.1

OBS: do not use ^4.0.1 (for some reason, it was pulling the last version [4.2.1] for me)

edited May 17, 2022 at 4:54

answered May 17, 2022 at 4:52

CiganoSA

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3 Comments

Tushar Asodariya Over a year ago

okay, Thanks for sharing. I was not aware of that 4.0.1 will work. I will try, let you know.

Mustafa Ali Dikçinar Over a year ago

same here 4.0.1 pulling 4.2.1 so i changed it

percent_indicator:      git:       url: https://github.com/diegoveloper/flutter_percent_indicator       ref: 686feb842d7144c3c45f8ce8d305a380416f3b67

a.utfull.day Over a year ago

Hats off this is exactly what the issue was!

Tuan · Accepted Answer · 2022-05-16 08:28:28Z

4

Your ? is wrong position. Try to change the code like this

// WidgetsBinding?.instance.addPostFrameCallback
-> WidgetsBinding.instance?.addPostFrameCallback

answered May 16, 2022 at 8:28

Tuan

2,4731 gold badge16 silver badges20 bronze badges

Comments

manhtuan21 · Accepted Answer · 2022-05-16 08:26:12Z

3

You should change

WidgetsBinding?.instance.addPostFrameCallback

to

WidgetsBinding.instance?.addPostFrameCallback

answered May 16, 2022 at 8:26

manhtuan21

3,5432 gold badges13 silver badges31 bronze badges

Comments

Eric · Accepted Answer · 2022-05-16 08:27:36Z

2

seems like the package put the null aware operator on the WidgetsBinding instead of the instance.

dart:162:5: Warning: The class 'WidgetsBinding' cannot be null. Try replacing '?.' with '.' WidgetsBinding?.instance.addPostFrameCallback((_) { ^^^^^^^^^^^^^^

it should be:

WidgetsBinding.instance?.addPostFrameCallback((_) {

answered May 16, 2022 at 8:27

Eric

5075 silver badges12 bronze badges

Comments

DiyorbekDev · Accepted Answer · 2022-05-16 10:00:00Z

2

Use percent_indicator version 4.0.1. Higher versions are customized to flutter 3.0 so you have an error. Or upgrade the flutter to version 3.0

edited May 16, 2022 at 10:00

answered May 16, 2022 at 9:31

DiyorbekDev

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3 Comments

Eric Over a year ago

not in this case. he is using Flutter 2.10.3

DiyorbekDev Over a year ago

look this github.com/diegoveloper/flutter_percent_indicator/commit/…

Eric Over a year ago

Yes i got you and you are right, but look at thread creators flutter doctor output.

Xuuan Thuc · Accepted Answer · 2022-05-16 08:29:30Z

1

change your percent_indicator dependency in pubspec.yaml to:

percent_indicator: #update flutter 3
git:
  url: https://github.com/XuannThucc/flutter_percent_indicator.git
  ref: be51b3d56e729ca1889f77a5f6311b5287fa611d

answered May 16, 2022 at 8:29

Xuuan Thuc

2,5511 gold badge8 silver badges24 bronze badges

3 Comments

Tushar Asodariya Over a year ago

Tried this, but still same error

Xuuan Thuc Over a year ago

Do you try run Flutter clean to clear cache and rebuild ?

Tushar Asodariya Over a year ago

Yes, after adding percent_indicator git repo to pubspec.yaml, I fired flutter clean and then flutter pub get, also I tried Invalidate/Restart android studio. But didn't worked.

zohaib mushwani · Accepted Answer · 2022-07-01 21:57:23Z

0

change

nb_utils: ^4.4.17

to

nb_utils: 4.4.17

in

pubspec.yaml

answered Jul 1, 2022 at 21:57

zohaib mushwani

11 bronze badge

Comments

Tushar Asodariya · Accepted Answer · 2022-07-02 06:12:38Z

0

Resolved, by adding percent_indicator lib to local project.

In that I changed, this

WidgetsBinding?.instance.addPostFrameCallback((_) {
                             ^^^^^^^^^^^^^^^^^^^^

to this

WidgetsBinding?.instance?.addPostFrameCallback((_) {

It's working

edited Jul 2, 2022 at 6:12

answered May 16, 2022 at 9:21

Tushar Asodariya

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2 Comments

user2570135 Over a year ago

I am having the same issue. What do you mean by "adding percent_indicator lib to local project"?

Tushar Asodariya Over a year ago

clone the github repo code and put it inside your project, and do the needful changes, or update your project to latest flutter version or packages

Neo · Accepted Answer · 2022-08-25 15:59:46Z

0

I was having this error just now, here is how I fixed:

I had a flutter dependency that I have to downgrade to a very older version, in your case is the percent_indicator-4.2.1.

go to pubspec.yaml

downgrade the percent_indicator-4.2.1 version to an older version

please let me know if it helped.

answered Aug 25, 2022 at 15:59

Neo

1

Comments

Abdelrahman Nasser · Accepted Answer · 2022-10-09 11:38:35Z

0

I faced the same problem, It worked for me by downgrading the package version.

Take a look at this repo: https://github.com/diegoveloper/flutter_percent_indicator/commit/f51e758488ecfbe56bff5c85a22bde3a00536013

answered Oct 9, 2022 at 11:38

Abdelrahman Nasser

437 bronze badges

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