Multi tool use

flutter NoSuchMethodError was thrown building MyAppMain(dirty):

I'm trying to implement the inherited widget but getting error as context got dirty for MyAppMain().

MyAppMain()

I/flutter (16558): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY
╞═══════════════════════════════════════════════════════════ I/flutter
(16558): The following NoSuchMethodError was thrown building
MyAppMain(dirty): I/flutter (16558): The getter 'mycounter' was called
on null. I/flutter (16558): Receiver: null I/flutter (16558): Tried
calling: mycounter

import 'package:flutter/material.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
int counter;
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(

primarySwatch: Colors.blue,
),
home:Scaffold(
appBar: new AppBar(

title: new Text('My App'),
),
body: MyAppMain(),
floatingActionButton: new CounterWidget(
),
),
);
}
}
class MyAppMain extends StatelessWidget {
@override
Widget build(BuildContext context) {
int _counter = 0;
int myinherited = MyInherited.of(context).mycounter;

_counter = myinherited+ 1;
return new Center(

child: new Column(

mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Text(
'You have pushed the button this many times:',
),

new Text(
'${_counter}',
style: Theme
.of(context)
.textTheme
.display1,
),
],
),
);
}

MyAppMain();
}

class CounterWidget extends StatefulWidget {


CounterWidget();

@override
MyInheritedState createState() => new MyInheritedState();

static MyInheritedState of(BuildContext context) {
return (context.inheritFromWidgetOfExactType(MyInherited) as MyInherited)
.data;
}
}

class MyInheritedState extends State<CounterWidget> {
String _myField;

// only expose a getter to prevent bad usage
String get myField => _myField;

int mycounter=0;

void onMyFieldChange(String newValue) {
setState(() {
_myField = newValue;
});
}

@override
Widget build(BuildContext context) {
return new MyInherited(
data: this,
mycounter:mycounter,
child: RaisedButton(child: new Text('click'), onPressed: () {
setState(() {
mycounter++;
});
},),
);
}
}

class MyInherited extends InheritedWidget {
final MyInheritedState data;
final int mycounter;
MyInherited({Key key, this.mycounter,this.data, Widget child})
: super(key: key, child: child);
static MyInherited of(BuildContext context){
return context.inheritFromWidgetOfExactType(MyInherited );
}
@override
bool updateShouldNotify(MyInherited old) {
return true;
}
}


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