New flutter update forces null safety?

Question

I just updated to flutter version 1.25.0-5.0.pre.92 and I'm getting lots of null-safety related errors in my code which was previously working fine. I have not opted into null safety in any way, all I did was run flutter upgrade, and now it assumes I want to use null safety.

These are the errors:

org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:165:81: Error: The parameter 'rowKeys' can't have a value of 'null' because of its type 'List<Key>', but the implicit default value is 'null'.
 - 'List' is from 'dart:core'.
 - 'Key' is from 'package:flutter/src/foundation/key.dart' ('../sdk/flutter/packages/flutter/lib/src/foundation/key.dart').
Try adding either an explicit non-'null' default value or the 'required' modifier.
  Widget _getCol3(BuildContext context, ScrollController controller, [List<Key> rowKeys]){
                                                                                ^^^^^^^
org-dartlang-app:/change_notifiers/theme_parameters.dart:17:5: Error: The value 'null' can't be assigned to a variable of type 'ThemeData' because 'ThemeData' is not nullable.
 - 'ThemeData' is from 'package:flutter/src/material/theme_data.dart' ('../sdk/flutter/packages/flutter/lib/src/material/theme_data.dart').
    null,
    ^
org-dartlang-app:/change_notifiers/theme_parameters.dart:27:35: Error: Method 'withOpacity' cannot be called on 'Color?' because it is potentially null.
 - 'Color' is from 'dart:ui'.
Try calling using ?. instead.
          color: Colors.grey[700].withOpacity(0.9),
                                  ^^^^^^^^^^^
org-dartlang-app:/change_notifiers/theme_parameters.dart:45:37: Error: Method 'withOpacity' cannot be called on 'Color?' because it is potentially null.
 - 'Color' is from 'dart:ui'.
Try calling using ?. instead.
            color: Colors.grey[700].withOpacity(0.9),
                                    ^^^^^^^^^^^
org-dartlang-app:/pages/heroes/page_heroes.dart:86:42: Error: The value 'null' can't be assigned to a variable of type 'Widget Function(BuildContext, Animation<double>, HeroFlightDirection, BuildContext, BuildContext)' because 'Widget Function(BuildContext, Animation<double>, HeroFlightDirection, BuildContext, BuildContext)' is not nullable.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'BuildContext' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'Animation' is from 'package:flutter/src/animation/animation.dart' ('../sdk/flutter/packages/flutter/lib/src/animation/animation.dart').
 - 'HeroFlightDirection' is from 'package:flutter/src/widgets/heroes.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/heroes.dart').
                        shuttleBuilder = null;
                                         ^
org-dartlang-app:/pages/heroes/page_heroes.dart:88:47: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
                      WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
                                              ^^^^^^^^^^^^^^^^^^^^
org-dartlang-app:/pages/heroes/page_heroes.dart:103:47: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
                      WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
                                              ^^^^^^^^^^^^^^^^^^^^
org-dartlang-app:/pages/heroes/page_heroes.dart:116:42: Error: The value 'null' can't be assigned to a variable of type 'Widget Function(BuildContext, Animation<double>, HeroFlightDirection, BuildContext, BuildContext)' because 'Widget Function(BuildContext, Animation<double>, HeroFlightDirection, BuildContext, BuildContext)' is not nullable.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'BuildContext' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'Animation' is from 'package:flutter/src/animation/animation.dart' ('../sdk/flutter/packages/flutter/lib/src/animation/animation.dart').
 - 'HeroFlightDirection' is from 'package:flutter/src/widgets/heroes.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/heroes.dart').
                        shuttleBuilder = null;
                                         ^
org-dartlang-app:/pages/heroes/page_heroes.dart:118:47: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
                      WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
                                              ^^^^^^^^^^^^^^^^^^^^
org-dartlang-app:/pages/heroes/page_heroes.dart:133:47: Error: Method 'addPostFrameCallback' cannot be called on 'WidgetsBinding?' because it is potentially null.
 - 'WidgetsBinding' is from 'package:flutter/src/widgets/binding.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/binding.dart').
Try calling using ?. instead.
                      WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
                                              ^^^^^^^^^^^^^^^^^^^^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:37:5: Error: The value 'null' can't be assigned to a variable of type 'TextEditingController' because 'TextEditingController' is not nullable.
 - 'TextEditingController' is from 'package:flutter/src/widgets/editable_text.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/editable_text.dart').
    null,
    ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:38:5: Error: The value 'null' can't be assigned to a variable of type 'TextEditingController' because 'TextEditingController' is not nullable.
 - 'TextEditingController' is from 'package:flutter/src/widgets/editable_text.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/editable_text.dart').
    null,
    ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:180:35: Error: The getter 'text' isn't defined for the class 'Object?'.
 - 'Object' is from 'dart:core'.
Try correcting the name to the name of an existing getter, or defining a getter or field named 'text'.
                    value = value.text;
                                  ^^^^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:183:33: Error: The argument type 'Object?' can't be assigned to the parameter type 'String'.
 - 'Object' is from 'dart:core'.
                    return Text(value, style: Theme.of(context).textTheme.headline3,);
                                ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:243:29: Error: The value 'null' can't be assigned to a variable of type 'Color' because 'Color' is not nullable.
 - 'Color' is from 'dart:ui'.
      colBackgroundColors: [null, null, null, Colors.green.withOpacity(0.4), Colors.red.withOpacity(0.4)],
                            ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:243:35: Error: The value 'null' can't be assigned to a variable of type 'Color' because 'Color' is not nullable.
 - 'Color' is from 'dart:ui'.
      colBackgroundColors: [null, null, null, Colors.green.withOpacity(0.4), Colors.red.withOpacity(0.4)],
                                  ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:243:41: Error: The value 'null' can't be assigned to a variable of type 'Color' because 'Color' is not nullable.
 - 'Color' is from 'dart:ui'.
      colBackgroundColors: [null, null, null, Colors.green.withOpacity(0.4), Colors.red.withOpacity(0.4)],
                                        ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:244:29: Error: The value 'null' can't be assigned to a variable of type 'Color' because 'Color' is not nullable.
 - 'Color' is from 'dart:ui'.
      rowBackgroundColors: [null, null, null, null, Colors.indigo.withOpacity(0.4)],
                            ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:244:35: Error: The value 'null' can't be assigned to a variable of type 'Color' because 'Color' is not nullable.
 - 'Color' is from 'dart:ui'.
      rowBackgroundColors: [null, null, null, null, Colors.indigo.withOpacity(0.4)],
                                  ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:244:41: Error: The value 'null' can't be assigned to a variable of type 'Color' because 'Color' is not nullable.
 - 'Color' is from 'dart:ui'.
      rowBackgroundColors: [null, null, null, null, Colors.indigo.withOpacity(0.4)],
                                        ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:244:47: Error: The value 'null' can't be assigned to a variable of type 'Color' because 'Color' is not nullable.
 - 'Color' is from 'dart:ui'.
      rowBackgroundColors: [null, null, null, null, Colors.indigo.withOpacity(0.4)],
                                              ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:246:26: Error: The value 'null' can't be assigned to a variable of type 'TextAlign' because 'TextAlign' is not nullable.
 - 'TextAlign' is from 'dart:ui'.
      columnAlignments: [null, null, null, null, TextAlign.right],
                         ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:246:32: Error: The value 'null' can't be assigned to a variable of type 'TextAlign' because 'TextAlign' is not nullable.
 - 'TextAlign' is from 'dart:ui'.
      columnAlignments: [null, null, null, null, TextAlign.right],
                               ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:246:38: Error: The value 'null' can't be assigned to a variable of type 'TextAlign' because 'TextAlign' is not nullable.
 - 'TextAlign' is from 'dart:ui'.
      columnAlignments: [null, null, null, null, TextAlign.right],
                                     ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:246:44: Error: The value 'null' can't be assigned to a variable of type 'TextAlign' because 'TextAlign' is not nullable.
 - 'TextAlign' is from 'dart:ui'.
      columnAlignments: [null, null, null, null, TextAlign.right],
                                           ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:247:19: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      colStyles: [null, null, null, null, Theme.of(context).textTheme.caption],
                  ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:247:25: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      colStyles: [null, null, null, null, Theme.of(context).textTheme.caption],
                        ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:247:31: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      colStyles: [null, null, null, null, Theme.of(context).textTheme.caption],
                              ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:247:37: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      colStyles: [null, null, null, null, Theme.of(context).textTheme.caption],
                                    ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:247:71: Error: A value of type 'TextStyle?' can't be assigned to a variable of type 'TextStyle' because 'TextStyle?' is nullable and 'TextStyle' isn't.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      colStyles: [null, null, null, null, Theme.of(context).textTheme.caption],
                                                                      ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:248:19: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      rowStyles: [null, null, null, null, Theme.of(context).textTheme.headline6],
                  ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:248:25: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      rowStyles: [null, null, null, null, Theme.of(context).textTheme.headline6],
                        ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:248:31: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      rowStyles: [null, null, null, null, Theme.of(context).textTheme.headline6],
                              ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:248:37: Error: The value 'null' can't be assigned to a variable of type 'TextStyle' because 'TextStyle' is not nullable.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      rowStyles: [null, null, null, null, Theme.of(context).textTheme.headline6],
                                    ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:248:71: Error: A value of type 'TextStyle?' can't be assigned to a variable of type 'TextStyle' because 'TextStyle?' is nullable and 'TextStyle' isn't.
 - 'TextStyle' is from 'package:flutter/src/painting/text_style.dart' ('../sdk/flutter/packages/flutter/lib/src/painting/text_style.dart').
      rowStyles: [null, null, null, null, Theme.of(context).textTheme.headline6],
                                                                      ^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:260:47: Error: The value 'null' can't be assigned to a variable of type 'bool' because 'bool' is not nullable.
          selected[rowsIds.indexOf(row.id)] = null;
                                              ^
/C:/Users/Dayan/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/extended_image-1.1.0/lib/src/extended_image.dart:786:44: Error: No named parameter with the name 'nullOk'.
    _invertColors = MediaQuery.of(context, nullOk: true)?.invertColors ??
                                           ^^^^^^
../sdk/flutter/packages/flutter/lib/src/widgets/media_query.dart:818:25: Context: Found this candidate, but the arguments don't match.
  static MediaQueryData of(BuildContext context) {
                        ^^
/C:/Users/Dayan/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/wave-0.0.8/lib/config.dart:46:13: Error: Method not found: 'throwNullError'.
            throwNullError('custom', 'colors` or `gradients');
            ^^^^^^^^^^^^^^
/C:/Users/Dayan/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/wave-0.0.8/lib/config.dart:60:13: Error: Method not found: 'throwNullError'.
            throwNullError('custom', 'durations');
            ^^^^^^^^^^^^^^
/C:/Users/Dayan/AppData/Local/Pub/Cache/hosted/pub.dartlang.org/wave-0.0.8/lib/config.dart:66:13: Error: Method not found: 'throwNullError'.
            throwNullError('custom', 'heightPercentages');
            ^^^^^^^^^^^^^^
org-dartlang-app:/pages/future_handling/page_future_handling.dart:32:10: Error: Field 'widgetToExport' should be initialized because its type 'Widget' doesn't allow null.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
  Widget widgetToExport;
         ^^^^^^^^^^^^^^
org-dartlang-app:/pages/future_handling/page_future_handling.dart:82:13: Error: Field 'widgetToExportKey' should be initialized because its type 'GlobalKey<State<StatefulWidget>>' doesn't allow null.
 - 'GlobalKey' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'State' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'StatefulWidget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
  GlobalKey widgetToExportKey;
            ^^^^^^^^^^^^^^^^^
org-dartlang-app:/pages/heroes/page_heroes.dart:33:10: Error: Field 'widgetToExport' should be initialized because its type 'Widget' doesn't allow null.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
  Widget widgetToExport;
         ^^^^^^^^^^^^^^
org-dartlang-app:/pages/heroes/page_heroes.dart:34:28: Error: Field 'shuttleBuilder' should be initialized because its type 'Widget Function(BuildContext, Animation<double>, HeroFlightDirection, BuildContext, BuildContext)' doesn't allow null.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'BuildContext' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
 - 'Animation' is from 'package:flutter/src/animation/animation.dart' ('../sdk/flutter/packages/flutter/lib/src/animation/animation.dart').
 - 'HeroFlightDirection' is from 'package:flutter/src/widgets/heroes.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/heroes.dart').
  HeroFlightShuttleBuilder shuttleBuilder;
                           ^^^^^^^^^^^^^^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:30:10: Error: Field 'col1' should be initialized because its type 'Widget' doesn't allow null.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
  Widget col1;
         ^^^^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:31:10: Error: Field 'col2' should be initialized because its type 'Widget' doesn't allow null.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
  Widget col2;
         ^^^^
org-dartlang-app:/pages/lightweight_table/page_lightweight_table.dart:32:10: Error: Field 'col3' should be initialized because its type 'Widget' doesn't allow null.
 - 'Widget' is from 'package:flutter/src/widgets/framework.dart' ('../sdk/flutter/packages/flutter/lib/src/widgets/framework.dart').
  Widget col3;
         ^^^^
Failed to compile application.

Is there any way to remove the null safety checks from my code or do am I forced to do the migration now? (it's a lot of work).

refer https://stackoverflow.com/a/66636686/5106574 – Jitesh Mohite Mar 15 '21 at 11:02 — Jitesh Mohite, Mar 15 '21 at 11:02

score 6 · Accepted Answer · answered Dec 13 '20 at 09:47

6

I managed to get my project working by:

Setting sdk: ">=2.7.0 <2.12.0" in pub spec.yaml
Restarting IDE
Running flutter clean
Running flutter create .

This seems to be a bug for me because, if you then run flutter clean again, the whole project goes back to using null-safety.

Also, I am using some of the newest features of Flutter, but if you don't need them you could just switch to the stable channel which does not have those changes yet.

answered Dec 13 '20 at 09:47

Joel Giménez

76
1
2

Thanks, I do need the latest features, like desktop suport... I decided to just migrate to null safety, I wanted to do it evetually anyways – Wish Master Dec 14 '20 at 11:32

score 1 · Answer 2 · answered Dec 07 '20 at 17:09

1

Change the "environment sdk" version with a lower bound. Details are at https://dart.dev/null-safety#enable-null-safety

answered Dec 07 '20 at 17:09

Randal Schwartz

39,428
4
43
70

i tried setting sdk: ">=2.7.0 <2.12.0", from what I read on your link, and got the same error... – Wish Master Dec 08 '20 at 18:23

score 1 · Answer 3 · answered Oct 26 '21 at 05:39

If you are interested in refactoring your code to meet the new Flutter SDK version, you can make the variables nullable by adding a ? after the variable type.

String? name;  // initialized to null by default
int? age = 36;  // initialized to non-null
age = null; // can be re-assigned to null

For more info, look at the explanation at this link: https://codewithandrea.com/videos/dart-null-safety-ultimate-guide-non-nullable-types/

New flutter update forces null safety?

3 Answers3