Flutter : Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null

Question

I run my flutter app on (Flutter 3.0 and dart sdk 2.17.0.

But now I found a warning here, like this -

/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_navigation/src/router_report.dart:53:22: Warning: Operand of null-aware
operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/widgets/bindi
 ng.dart').
      WidgetsBinding.instance!.addPostFrameCallback((_) {
                     ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_navigation/src/snackbar/snackbar.dart:452:22: Warning: Operand of
null-aware operation '!' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
    SchedulerBinding.instance!.addPostFrameCallback(
                     ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_navigation/src/extension_navigation.dart:357:24: Warning: Operand of
null-aware operation '!' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
      SchedulerBinding.instance!.addPostFrameCallback((_) {
                       ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_navigation/src/extension_navigation.dart:468:24: Warning: Operand of
null-aware operation '!' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
      SchedulerBinding.instance!.addPostFrameCallback((_) {
                       ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_state_manager/src/simple/get_controllers.dart:90:20: Warning: Operand
of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/widgets/bindi
 ng.dart').
    WidgetsBinding.instance!.addObserver(this);
                   ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_state_manager/src/simple/get_controllers.dart:96:20: Warning: Operand
of null-aware operation '!' has type 'WidgetsBinding' which excludes null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/widgets/bindi
 ng.dart').
    WidgetsBinding.instance!.removeObserver(this);
                   ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_state_manager/src/rx_flutter/rx_notifier.dart:130:22: Warning: Operand
of null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
    SchedulerBinding.instance?.addPostFrameCallback((_) => onReady());
                     ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/get-4.
6.1/lib/get_state_manager/src/rx_flutter/rx_disposable.dart:20:22: Warning: Operand
of null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
    SchedulerBinding.instance?.addPostFrameCallback((_) => onReady());
                     ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/flutte
r_easyloading-3.0.3/lib/src/widgets/overlay_entry.dart:35:26: Warning: Operand of
null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
    if (SchedulerBinding.instance?.schedulerPhase ==
                         ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/flutte
r_easyloading-3.0.3/lib/src/widgets/overlay_entry.dart:37:24: Warning: Operand of
null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
      SchedulerBinding.instance?.addPostFrameCallback((_) {
                       ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/flutte
r_easyloading-3.0.3/lib/src/widgets/container.dart:64:24: Warning: Operand of
null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
      SchedulerBinding.instance?.schedulerPhase ==
                       ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/flutte
r_easyloading-3.0.3/lib/src/widgets/container.dart:101:24: Warning: Operand of
null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
      SchedulerBinding.instance?.addPostFrameCallback((_) => completer
                       ^
/usr/local/Caskroom/flutter/2.0.2/flutter/.pub-cache/hosted/pub.dartlang.org/flutte
r_easyloading-3.0.3/lib/src/widgets/container.dart:112:24: Warning: Operand of
null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart'
 ('/usr/local/Caskroom/flutter/2.0.2/flutter/packages/flutter/lib/src/scheduler/bin
 ding.dart').
      SchedulerBinding.instance?.addPostFrameCallback((_) => completer
                       ^
Syncing files to device iPhone SE (3rd generation)...              805ms

What is the problem. It's not show in previous version of flutter.

Does this answer your question? Warning: Operand of null-aware operation '!' has type 'WidgetsBinding' which excludes null. when upgrading to flutter 3.0.0 — Mohammad Rabiee Nasri
– Mohammad Rabiee Nasri, Commented May 16, 2022 at 20:18

Eric · Accepted Answer · 2022-05-16 06:40:24Z

0

In Flutter 3.0

SchedulerBinding.instance!.addPostFrameCallback(...);

became

SchedulerBinding.instance.addPostFrameCallback(...);

seems like the bindings package has some Schedulerbindings coded inside and needs to be updated.

You can copy the package locally and change the code inside that package.

Or change the dependencies.... or wait until that package is updated and revert to Flutter 2.10.5

You can read about the changes to Flutter 3.0 Here

I use a tool for changing versions Flutter Sidekick you can chose diffferent Flutter versions for different project.

answered May 16, 2022 at 6:40

Eric

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