NoSuchMethodError: The getter data was called on null, receiver: null - firebase

Question

I am trying to create a detail screen to display my Firebase data from the database, and show the image along with some text data including the number of items, date, and geolocation. Is there a way to determine why the data is returning null? The navigator should navigate to the DetailPage.
Here is my Main file -
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:wasteagram/pages/create_waste.dart';
import 'package:wasteagram/services/crud.dart';
import 'pages/create_waste.dart';
import 'pages/detail_screen.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Wasteagram - ',
theme: new ThemeData(
primarySwatch: Colors.deepOrange,
),
home: new MyHomePage(title: 'Wasteagram - '),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
CrudMethods crudMethods = new CrudMethods();
Stream wasteStream;
Widget WasteList() {
return Container(
child: wasteStream != null ? Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
StreamBuilder(
stream: wasteStream,
builder: (context, snapshot) {
return ListView.builder(
padding: EdgeInsets.symmetric(horizontal: 16),
itemCount: snapshot.data.documents.length,
shrinkWrap: true,
itemBuilder: (context, index){
return WidgetTile(
wastedate:
snapshot.data.documents[index].data['wastedate'],
wastenumber:
snapshot.data.documents[index].data['wastenumber']
);
});
},)
],
) : Container(
alignment: Alignment.center,
child: CircularProgressIndicator(),
),
);
}
void initState() {
super.initState();
crudMethods.getData().then((result) {
wasteStream = result;
});
}
#override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text(widget.title),
),
body: WasteList(),
floatingActionButton: new FloatingActionButton(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => CameraScreen())
);
},
child: new Icon(Icons.add),
),
floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
);
}
}
class WidgetTile extends StatelessWidget {
String wastedate, wastenumber;
WidgetTile({#required this.wastedate, #required this.wastenumber});
#override
Widget build(BuildContext context) {
return ListTile(
title: Text(wastedate),
trailing: Text(wastenumber),
onTap: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => DetailPage())
);
}
);
}
}
Here is my detail_screen.dart
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:wasteagram/data/firestore_service.dart';
class DetailPage extends StatefulWidget {
final DocumentSnapshot post;
DetailPage({this.post});
#override
_DetailPageState createState() => _DetailPageState();
}
class _DetailPageState extends State<DetailPage> {
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.post.data["wastedate"])
),
body: Center(
child: Container(
child: Column(
children: <Widget> [
Image.network(widget.post.data["image"]),
Text(widget.post.data["wastedate"]),
Text(widget.post.data["wastenumber"]),
Text(widget.post.data["wastelocation"].toString()),
]
)
)
),
);
}
}

Answer 1

You are not passing DocumentSnapshot to Detail Page.
Try this:
Widget WasteList() {
return Container(
child: wasteStream != null ? Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
StreamBuilder(
stream: wasteStream,
builder: (context, snapshot) {
return ListView.builder(
padding: EdgeInsets.symmetric(horizontal: 16),
itemCount: snapshot.data.documents.length,
shrinkWrap: true,
itemBuilder: (context, index){
return WidgetTile(
wastedate:
snapshot.data.documents[index].data['wastedate'],
wastenumber:
snapshot.data.documents[index].data['wastenumber'],
post:
snapshot.data.documents[index]
);
});
},)
],
) : Container(
alignment: Alignment.center,
child: CircularProgressIndicator(),
),
);
}
class WidgetTile extends StatelessWidget {
String wastedate, wastenumber;
DocumentSnapshot post;
WidgetTile({#required this.wastedate, #required this.wastenumber,#required this.post});
#override
Widget build(BuildContext context) {
return ListTile(
title: Text(wastedate),
trailing: Text(wastenumber),
onTap: () {
Navigator.push(
context,
MaterialPageRoute(builder: (context) => DetailPage(post: post))
);
}
);
}
}