context undefined in Navigator.push - flutter

Question

I'm creating a custom AppBar that I can use across multiple pages. customappbar.dart
class CustomAppBar extends AppBar {
CustomAppBar({Key key, Widget title})
: super(
key: key,
title: title,
actions: <Widget>[
IconButton(
icon: Icon(Icons.directions_car),
onPressed: () {
Navigator.push(
context, //UNDEFINED
MaterialPageRoute(
builder: (context) => NewPage(),
),
);
},
),
],
);
}
Here's an example of where it's going to go. newpage.dart
class _ NewPageState extends State<NewPage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: CashOnHandAppBar(
title: Text('New Page'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[],
),
),
);
}
}
context is getting of undefined. is the build method missing?

Answer 1

You are extending AppBar class it will not work for custom appbar you have to extend StatelessWidget and implement PreferredSizeWidget class for custom appbar
Here is the working example of custom appbar :-
import 'package:flutter/material.dart';
class SimpleAppBar extends StatelessWidget implements PreferredSizeWidget {
final String _title;
final bool centerTitle;
SimpleAppBar(this._title, {this.centerTitle = false, Key key})
: preferredSize = Size.fromHeight(56.0),
super(key: key);
#override
final Size preferredSize; // default is 56.0
#override
Widget build(BuildContext context) {
return AppBar(
title: Text(_title),
centerTitle: centerTitle,
);
}
}
And instead of adding function directly into custom appbar pass function reference to the class constructor
Need to pass below function add reference :-
onPressed: () {
Navigator.push(
context, //UNDEFINED
MaterialPageRoute(
builder: (context) => NewPage(),
),