How to get firestore data in another widget - firebase

Question

What the app can do so far: So far, I have an app that shows markers on a Google Map that get the coordinates from Firestore.
What I want: I want that when the user presses a marker, he comes to another screen on which some more data is presented (the data is also on the firestore).
The problem: I don't know how to get the data (for example the name) on the screen on which the details are to be displayed.
I have a onTap function, which calls goToDetailPage()
That`s the goToDetailPage() function:
void goToDetailPage() {
Navigator.of(context).push(new MaterialPageRoute(
builder: (BuildContext context) => new detailPage()));
}
That's the code for "drawing" the marker:
void initMarker(specify, specifyId) async {
var markerIdVal = specifyId;
final MarkerId markerId = MarkerId(markerIdVal);
final Marker marker = Marker(
markerId: markerId,
position:
LatLng(specify['location'].latitude, specify['location'].longitude),
infoWindow: InfoWindow(title: specify['name'], snippet: 'Shop'),
onTap: () {
goToDetailPage();
});
print(specify['location'].latitude);
nameTest = specify['name'];
setState(() {
markers[markerId] = marker;
print(markerId.toString() + '__________________________');
});
}
That's the code from the detail Page:
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Detail Page'),
),
body: Column(children: <Widget>[Text(specify['name'])]),
);
The problem is that the specify from the specify['name'] in the detail page is red underlined and I don`t know what's the reason for that.

Answer 1

In the second page:
class Tester extends StatefulWidget {
String dataFromLastPage;
Tester({Key key, this.dataFromLastPage}) : super(key: key);
#override
_TesterState createState() => _TesterState();
}
class _TesterState extends State<Tester> {
#override
Widget build(BuildContext context) {
return Text(widget.dataFromLastPage); //"thisWillGoToTheNextPage!"
}
}
When navigating to that page, send data like this:
Navigator.of(context).push(new MaterialPageRoute(
builder: (BuildContext context) => new Tester(dataFromLastPage: 'thisWillGoToTheNextPage!')));

Answer 2

Try and go accoording to what the docs say : https://firebase.flutter.dev/docs/firestore/usage/#realtime-changes
However , there are several things the doc doesn't specify like
To use firestore first , you need to initialize you firestore app , for that you just write a specific piece of code in the main method of your dart file
void main() async{
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
runApp(MyApp());
}
To connect to your firestore database , simply type in your widget build function
CollectionReference <Variable name> = FirebaseFirestore.instance.collection(<Name of collection as string>);
Now if you are creating a list , you can simply use a StreamBuilder function and get the data in your document via (initialize snapshot as given in the documentation)
snapshot.data.docs[index].data()[<Identifier of your document such as
'Name' or 'location'>]