Navigator operation requested with a context that does not include a Navigator - Flutter - flutter

Question

i have a problem with navigator in my flutter file.
The problem is in my GestureDetector in _listItem, after tap on object, in my debug console throw me:
The following assertion was thrown while handling a gesture:
Navigator operation requested with a context that does not include a Navigator.
The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.
I don't have idea why this not work for me, can abybody help me?
below is my code:
class _HomePageState extends State<HomePage> {
#override
Widget build(BuildContext context) {
return MaterialApp(
home:Scaffold(
appBar: PreferredSize(
preferredSize: Size.fromHeight(100.0),
child: AppBar(
iconTheme: IconThemeData(color: Color.fromRGBO(9, 133, 46, 100)),
backgroundColor: Colors.white,
actions: <Widget>[
IconButton(
icon: Icon(
Icons.shopping_cart,
color: Color.fromRGBO(9, 133, 46, 100),
),
onPressed: (){
print('klikniete');
},
),
],
),
),
body: Builder(
builder: (context) => Container(
child: FutureBuilder(
future: fetchOrders(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (_ordersForDisplay.length == null) {
return Container(
child: Center(child: Text("Ładowanie...")),
);
} else {
return ListView.builder(
itemCount: _ordersForDisplay.length + 1,
itemBuilder: (BuildContext context, int index) {
return index == 0 ? _searchBar() : _listItem(index - 1);
},
);
}
},
),
),
),
)
);
}
_listItem(index) {
return GestureDetector(
onTap: () => Navigator.of(context).push(
MaterialPageRoute(builder: (context) => DetailPage(item: _ordersForDisplay[index])),
),
child: Card(
child: Padding(
padding: const EdgeInsets.only(
top: 32.0, bottom: 32.0, left: 16.0, right: 16.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(
_ordersForDisplay[index].firstName,
style: TextStyle(fontSize: 22, fontWeight: FontWeight.bold),
),
Text(
_ordersForDisplay[index].lastName,
style: TextStyle(
color: Colors.grey.shade600
),
),
],
),
),
),
);
}
}
class DetailPage extends StatelessWidget {
final Order item;
const DetailPage({this.item});
#override
Widget build(BuildContext context) {
return Center(
child: Text('${item.firstName} - ${item.lastName}')
);
}
}

Answer 1

Try changing your methods args as.
_listItem(index, context) { //Changes here
....
}
And pass the context where you called it.
return index == 0 ? _searchBar() : _listItem(index - 1,context);