Missing Null Safety on WidgetsBinding & SchedulerBinding

[Rishabh-Invizio]

The image_editor_plus: ^0.1.3 package in our project, is using the latest version of nb_utils: 4.5.1.
Our Flutter project's environment sdk contraints are:

environment:
  sdk: ">=2.16.2 <3.0.0"

When building the app for Android, the build fails with the following error:

../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/utils/common.dart:200:29: Error: Method 'addPostFrameCallback' cannot be called on 'SchedulerBinding?' because it is potentially null.
 - 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/packages/flutter/lib/src/scheduler/binding.dart').
Try calling using ?. instead.
  SchedulerBinding.instance.addPostFrameCallback((_) => onCreated?.call());
                            ^^^^^^^^^^^^^^^^^^^^
../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/utils/after_layout.dart:12:10: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
        .addPostFrameCallback((_) => afterFirstLayout(context));
         ^^^^^^^^^^^^^^^^^^^^
../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/OverlayCustomWidget.dart:59:31: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
      WidgetsBinding.instance.addPostFrameCallback((_) => showOverlay());
                              ^^^^^^^^^^^^^^^^^^^^
../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/OverlayCustomWidget.dart:66:29: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
    WidgetsBinding.instance.addPostFrameCallback((_) => syncWidgetAndOverlay());
                            ^^^^^^^^^^^^^^^^^^^^
../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/OverlayCustomWidget.dart:72:29: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
    WidgetsBinding.instance.addPostFrameCallback((_) => syncWidgetAndOverlay());
                            ^^^^^^^^^^^^^^^^^^^^
../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/TimerWidget.dart:44:29: Error: Method 'addObserver' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
    WidgetsBinding.instance.addObserver(this);
                            ^^^^^^^^^^^
../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/TimerWidget.dart:59:29: Error: Method 'removeObserver' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../Flutter%20SDK/Flutter%20Git%20Repository/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
    WidgetsBinding.instance.removeObserver(this);
                            ^^^^^^^^^^^^^^


FAILURE: Build failed with an exception.

It seems you have missed null safety on WidgetsBinding and SchedulerBinding methods, causing the exception to be thrown. Can you get please provide a fix for this asap?

[BenCherif]

the same issue here :D

[bhoominn]

You have to update for Flutter SDK version to 3.0.0.

Or you can use nb_utils version 4.5.0.

[heydc7]

I am using Flutter 3.0, but still, it is giving the same errors.

[bhoominn]

Please show errors here.

[heydc7]

../../../Developer/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/TimerWidget.dart:44:20: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.

• 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../Developer/flutter/packages/flutter/lib/src/widgets/binding.dart').
  WidgetsBinding.instance?.addObserver(this);
  ^
  ../../../Developer/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/TimerWidget.dart:59:20: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.
• 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../Developer/flutter/packages/flutter/lib/src/widgets/binding.dart').
  WidgetsBinding.instance?.removeObserver(this);
  ^
  ../../../Developer/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/OverlayCustomWidget.dart:59:22: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.
• 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../Developer/flutter/packages/flutter/lib/src/widgets/binding.dart').
  WidgetsBinding.instance?.addPostFrameCallback((_) => showOverlay());
  ^
  ../../../Developer/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/OverlayCustomWidget.dart:66:20: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.
• 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../Developer/flutter/packages/flutter/lib/src/widgets/binding.dart').
  WidgetsBinding.instance?.addPostFrameCallback((_) => syncWidgetAndOverlay());
  ^
  ../../../Developer/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/widgets/OverlayCustomWidget.dart:72:20: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.
• 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../Developer/flutter/packages/flutter/lib/src/widgets/binding.dart').
  WidgetsBinding.instance?.addPostFrameCallback((_) => syncWidgetAndOverlay());
  ^
  ../../../Developer/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/utils/common.dart:200:20: Warning: Operand of null-aware operation '?.' has type 'SchedulerBinding' which excludes null.
• 'SchedulerBinding' is from 'package:flutter/src/scheduler/binding.dart' ('../../../Developer/flutter/packages/flutter/lib/src/scheduler/binding.dart').
  SchedulerBinding.instance?.addPostFrameCallback((_) => onCreated?.call());
  ^
  ../../../Developer/flutter/.pub-cache/hosted/pub.dartlang.org/nb_utils-4.5.1/lib/src/utils/after_layout.dart:11:20: Warning: Operand of null-aware operation '?.' has type 'WidgetsBinding' which excludes null.
• 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../../../Developer/flutter/packages/flutter/lib/src/widgets/binding.dart').
  WidgetsBinding.instance?.addPostFrameCallback((_) => afterFirstLayout(context));

[bhoominn]

Ok, show flutter doctor command output.

[heydc7]

[heydc7]

(base) dhanraj@192 ytcards % flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.0.0, on macOS 12.3.1 21E258 darwin-x64, locale en-IN)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 13.3.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2021.2)
[✓] VS Code (version 1.67.0)
[✓] Connected device (3 available)
! Error: Dhanraj’s iPhone is busy: Waiting to connect and unlock the device. Xcode will continue when Dhanraj’s iPhone is finished. (code -10)
! Error: iPad is not connected. Xcode will continue when iPad is connected. (code -13)
[✓] HTTP Host Availability

• No issues found!

[athulpp]

same error in my project also when implementing this package

[bhoominn]

Upgrade this package to the latest version 4.5.2 and check if your issue is solved or not.

[heydc7]

Yes, All errors are gone. Working smoothly ✨ Thank you!!!

[AlaaMarawi]

Upgrade this package to the latest version 4.5.2 and check if your issue is solved or not.

It is solved with v4.5.2 & flutter 2.8.1. but this means I can't use later versions :(

UPDATE: I upgraded to flutter 3 -> it is solved (in both 4.5.2 & the latest)