error when I use raisedButton in a widget - flutter

Question

I am writing my first flutter app and i created two classes.
Those two classes represent two pages that i wish to navigate between and I am facing an issue with the "raisedButton".
The first class has 2 widgets and the button only works in one of them! whenever I try to cut+ paste the button to the desired widget => I get the following error:
The method 'findAncestorStateOfType' was called on null.
Receiver: null
Tried calling: findAncestorStateOfType()
I don't know what they mean by that.
Any help is appreciated.
class FirstRoute extends StatelessWidget {
Widget _contactList(String name, String image,[BuildContext context]) {
return Padding(
padding: const EdgeInsets.all(8.0),
child: ListTile(
leading: CircleAvatar(
backgroundColor: Colors.red,
backgroundImage: AssetImage(image),
radius: 35.0,
child: Text(nameInitial,
style: TextStyle(fontWeight: FontWeight.bold, fontSize: 20.0)),
),
title: Text(name),
trailing: RaisedButton(
textColor: Colors.white,
color: Colors.blue,
child: Text('Details'),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => Details()),
);
},
),
),
);
}

Answer 1

you can use a named route by calling the Navigator.pushNamed(context,'/home'); Named routes allow for parameter passing '/customer/:${customer.id}'. the routing paths are defined onGenerateRoute attribute assigned to routing information
class _AppWidgetState extends State<AppWidget>{
bool _bright=false;
_brightnessCallback().
{setState(()=>_bright=!_bright);debugPrint("brightnessCallback fired");}
#override
Widget build(BuildContext context){
return MaterialApp(
title: "Flutter demo",
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHome2Widget(),
onGenerateRoute: handleRoute
);
}}
Route<dynamic> handleRoute(RouteSettings routeSettings)
{
List<String> nameParam= routeSettings.name.split(":");
String name=nameParam[0];
//int id=int.tryParse(nameParam[1]);
Widget childWidget;
if(name=="/Home")
{
childWidget=MyHome2Widget();
}else if(name=="/Summary")
{
childWidget=SummaryWidget();
}
return MaterialPageRoute(
builder:(context)=>childWidget
);
}