Error: The method 'ancestorStateOfType' isn't defined for the class 'BuildContext'

Question

When using the class Bloc provider as follows, I get the error:

'The method 'ancestorInheritedElementForWidgetOfExactType' isn't defined for the type 'BuildContext'.'

So I replaced this line context.ancestorInheritedElementForWidgetOfExactType(type)?.widget;

with this line context.getElementForInheritedWidgetOfExactType<_BlocProviderInherited<T>>().widget;

but then I get the following Error:

Error output from Xcode build:
↳
** BUILD FAILED **

Xcode's output:
↳
../../../development/flutter/.pub-cache/hosted/pub.dartlang.org/dynamic_theme-1.0.1/lib/dynamic_theme.dart:25:20: Error: The method 'ancestorStateOfType' isn't defined for the class 'BuildContext'.
 - 'BuildContext' is from 'package:flutter/src/widgets/framework.dart' ('../../../development/flutter/packages/flutter/lib/src/widgets/framework.dart').
Try correcting the name to the name of an existing method, or defining a method named 'ancestorStateOfType'.
    return context.ancestorStateOfType(const TypeMatcher<DynamicThemeState>());
                   ^^^^^^^^^^^^^^^^^^^

Command PhaseScriptExecution failed with a nonzero exit code
note: Using new build system
note: Building targets in parallel
note: Planning build
note: Constructing build description

Could not build the precompiled application for the device.

Error launching application on iPhone 

This is the Bloc Provider i am using:

class BlocProvider<T extends BlocBase> extends StatefulWidget {
   BlocProvider({
   Key key,
   @required this.child,
   @required this.bloc,}) : super(key: key);
   final Widget child;
   final T bloc;
   @override
   _BlocProviderState<T> createState() => _BlocProviderState<T>();

   static T of<T extends BlocBase>(BuildContext context) {
   final type = _typeOf<_BlocProviderInherited<T>>();
   _BlocProviderInherited<T> provider =
   context.ancestorInheritedElementForWidgetOfExactType(type)?.widget;
   return provider?.bloc;
  }
}

I am on the Master channel, Flutter (Channel master, 1.26.0-2.0.pre.275)

Jassy

If I remember correctly, your initial error means that it does not find the bloc instance in the upstream widget tree – Steviestevy

On Flutter dev channel it is working. Flutter (Channel dev, 1.26.0-1.0.pre). But unfortunately other things are not working on the dev channel. – Jassy

Answer 1

after upgrade dev channel was almost the same issue

.pub-cache/hosted/pub.dartlang.org/dynamic_theme-1.0.1/lib/dynamic_theme.dart:25:20: Error: The method 'ancestorStateOfType' isn't defined for the class 'BuildContext'.
'BuildContext' is from 'package:flutter/src/widgets/framework.dart' ('/home/liudmila/snap/flutter/common/flutter/packages/flutter/lib/src/widgets/framework.dart').
Try correcting the name to the name of an existing method, or defining a method named 'ancestorStateOfType'.

with block 4.0.0

just change this in file .pub-cache/../dynamic_theme.dart:25:20

context.ancestorStateOfType()

on that

context.findAncestorStateOfType<DynamicThemeState>();

thats temp solution, but app is work

Marjoriemarjory

I was able to fix my project – Overrule

Thanks, this workaround saved my life until we can update this dependency – Zincate

Answer 2

You are using an old version of flutter_bloc, first you should upgrade it.

But, in fact the real problem is that context.ancestorInheritedElementForWidgetOfExactType(type) is deprecated in favor of context.getElementForInheritedWidgetOfExactType<T>() but still available in the stable channel, but in master is already removed.

Then it is necessary to update your code because Bloc has suffered breaking changes.

UPDATE: The mentioned change is already in the stable channel.

Curie

I did update flutter_bloc to ^6.1.1 and did also try the pre release ^7.0.0-nullsafety.0, but none of them are working on the Master channel. Is there a new implementation for the bloc_provider? For me it seems like the Method 'ancestorStateOfType' is not available in the BuildContext class. – Jassy

the context.ancestorStateOfType() is also deprecated – Curie

Answer 3

try changing the packages version in pubspec.yaml it worked for me i changed provider version to 5.0.0 , then it started working

Neglect

Please add some code snippets to your answer to be more clear. – Skeens

Answer 4

This error is caused when the package gets outdated. So upgrading the package is one solution to it. But sometimes, even upgrading the package does not work because maybe the creator of the package has not upgraded it or has abandoned it. In that case switch to other package.

In this particular case upgrading flutter_bloc might work.

Another similar problem i faced with GradientAppBar. It gives same error as above. The solution is to use AppBar beacuse AppBar now supports gradient inside it.

AppBar(
      flexibleSpace: Container(
      decoration: BoxDecoration(
        gradient: LinearGradient(
        begin: Alignment.topCenter,
        end: Alignment.bottomCenter,
        colors: [
          Colors.amber[700],
          Colors.grey[800],
        ]
      )
    )
  ),

I am posting about gradient app bar here because I came in this post to find the solution about GradientAppBar but couldn't find.

Parallelepiped

Answer 5

change it from

context.findAncestorStateOfType<DynamicThemeState>();

to

context.findAncestorStateOfType<*Your_Library*>();

this will work

Crackpot

Answer 6

context.findAncestorStateOfType<your_library_name>()

In my case this error occurs in animated_circular_chart so, I've added this line to my animated_circular_chart.dart

Gagliardi

Answer 7

Just change it to this it works.

context.findAncestorStateOfType<DynamicThemeState>();

it is just code update in new flutter version, older one is depreciated

Threnody

Please add some explanation to your answer – Fulkerson

it is just code update in new flutter version older one is depreciated. – Threnody

So add it into your aswer – Fulkerson