Unhandled Exception: inheritFromWidgetOfExactType(_LocalizationsScope) or inheritFromElement() was called before _ScreenState.initState() completed

Question

I am calling initial method to load data from API using initState. But it is resulting me an error. Here is error:

Unhandled Exception: inheritFromWidgetOfExactType(_LocalizationsScope) or inheritFromElement() was called before _ScreenState.initState() completed.
When an inherited widget changes, for example if the value of Theme.of() changes, its dependent widgets are rebuilt. If the dependent widget's reference to the inherited widget is in a constructor or an initState() method, then the rebuilt dependent widget will not reflect the changes in the inherited widget.

My code is:

@override
  void initState() {
    super.initState();

    this._getCategories();
  }

  void _getCategories() async {
    AppRoutes.showLoader(context);
    Map<String, dynamic> data = await apiPostCall(
      apiName: API.addUser,
      context: context,
      parameterData: null,
      showAlert: false,
    );
    if(data.isNotEmpty){
      AppRoutes.dismissLoader(context);
      print(data);

    }else {
      AppRoutes.dismissLoader(context);
    }
   }

is your _getCategories is in builder method ? how did you get context? — Praneeth Dhanushka Fernando, May 31 '19 at 12:47

siega · Accepted Answer · 2022-03-31T11:49:32.280

124

You need to call _getCategories after initState has completed.


@override
void initState() {
   super.initState();

   Future.delayed(Duration.zero, () {
      this._getCategories();
   });

   // Could do this in one line: Future.delayed(Duration.zero, this._getCategories);
}

Also, you could do this on a different way, using addPostFrameCallback. To make this task easier, you could create a mixin to be added to StatefulWidgets.

mixin PostFrameMixin<T extends StatefulWidget> on State<T> {
  void postFrame(void Function() callback) =>
      WidgetsBinding.instance?.addPostFrameCallback(
        (_) {
          // Execute callback if page is mounted
          if (mounted) callback();
        },
      );
}

Then, you just need to plug this mixin to you page, like that:

class _MyPageState extends State<MyPage> with PostFrameMixin {
  @override
  void initState() {
    super.initState();

    postFrame(_getCategories);
  }
}

edited Mar 31 '22 at 11:49

answered May 31 '19 at 20:24

siega

2,508
1
19
22

1

Thanks, It worked. Can you explain how this worked? – Dipendra Sharma Sep 27 '19 at 08:06
2

Is it a safe solution? what if init is not yet finished? – bashan Sep 28 '19 at 16:59
I think using didChangeDependencies instead of init state for getCategories is a better alternative to this answer.....because it gets called after init state completes. – Dharmik Thakkar Dec 01 '20 at 14:05
didChangeDependencies can be called more than once. That's why you must avoid using it for this purpose. – siega Sep 27 '22 at 15:08

score 40 · Answer 2 · answered Apr 15 '20 at 11:10

40

Use the didChangeDependencies method which gets called after initState.

For your example:

@override
void initState() {
  super.initState();
}

@override
void didChangeDependencies() {
  super.didChangeDependencies();

  this._getCategories();
}

void _getCategories() async {
  // Omitted for brevity
  // ...

 }

answered Apr 15 '20 at 11:10

Emilio Brandon Flanagan

1,142
1
12
13

15

This is could result in multiple calls to _getCatergories() as didChangeDependencies() is called multiple times. So if the _getCatergories() involves network calls or refreshing state, this would be very bad. – Susheel Karam Apr 28 '20 at 07:44
this works not only for this case but also for this other question https://stackoverflow.com/questions/60363665/dependoninheritedelement-was-called-before-initstate-in-flutter – Obum Feb 17 '22 at 10:02

score 35 · Answer 3 · answered Apr 10 '20 at 09:38

Adding a frame callback might be better than using Future.delayed with a zero duration - it's more explicit and clear as to what is happening, and this kind of situation is what frame callback was designed for:

@override
  void initState() {
    super.initState();

    WidgetsBinding.instance.addPostFrameCallback((_) async {
      _getCategories();
    });
  }

MJ Montes · Answer 4 · 2023-03-30T15:33:52.077

8

an alternative is to put it inside PostFrameCallback which is between initState and Build.

@override
void initState() {
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) => getData());
}
    
Future<void> getData() async {
// perform fetch logic
}

edited Mar 30 '23 at 15:33

answered May 19 '20 at 08:31

MJ Montes

3,234
1
19
21

CopsOnRoad · Answer 5 · 2021-11-05T16:57:43.133

2

There are many ways to solve this problem, override initState method:

@override
void initState() {
  super.initState();
  // Use any of the below code here. 
}

Using SchedulerBinding mixin:

SchedulerBinding.instance!.addPostFrameCallback((_) {
  // Call your function
});

Using Future class:

Future(() {
  // Call your function
});

Using Timer class:
```
Timer(() {
  // Call your function
});
```

edited Nov 05 '21 at 16:57

answered Feb 03 '21 at 16:59

CopsOnRoad

237,138
77
654
440

score -1 · Answer 6 · answered Dec 26 '19 at 16:24

-1

The best solution i think is use the context from the Widget build. And paste the method _getCategories(context) after the build with the context from the tree. So there is no problem with the widget tree.

answered Dec 26 '19 at 16:24

Kfarsoft

59
1
3

Unhandled Exception: inheritFromWidgetOfExactType(_LocalizationsScope) or inheritFromElement() was called before _ScreenState.initState() completed

6 Answers6

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