I get this error bad state stream has already been listened to when i added bottomNavigationBar to FirestoreCRUDPage. In all other pages i will use the same stream. but when i tap on bottom navigation to go to a new page i get that error, it tries to listen to the same stream again.
is there a way to prevent that?
thanks for the great work

In the project signup_screen_card in the file SignUp.dart add comma after parameter fontSize of the method buildText.

When I added more than 7 items, and I slide down the list and slide up, it shows an error

I/flutter ( 7906): Another exception was thrown: 'package:flutter/src/widgets/sliver.dart': Failed assertion: line 1059 pos 14: '_childElements.containsKey(index)': is not true.
I/flutter ( 7906): Another exception was thrown: 'package:flutter/src/rendering/sliver_multi_box_adaptor.dart': Failed assertion: line 470 pos 12: 'child.hasSize': is not true.
I/flutter ( 7906): Another exception was thrown: 'package:flutter/src/widgets/sliver.dart': Failed assertion: line 1059 pos 14: '_childElements.containsKey(index)': is not true.
I/flutter ( 7906): Another exception was thrown: 'package:flutter/src/rendering/sliver_multi_box_adaptor.dart': Failed assertion: line 470 pos 12: 'child.hasSize': is not true.
I/flutter ( 7906): Another exception was thrown: 'package:flutter/src/widgets/sliver.dart': Failed assertion: line 1059 pos 14: '_childElements.containsKey(index)': is not true.
I/flutter ( 7906): Another exception was thrown: 'package:flutter/src/rendering/sliver_multi_box_adaptor.dart': Failed assertion: line 470 pos 12: 'child.hasSize': is not true.
I/flutter ( 7906): Another exception was thrown: 'package:flutter/src/widgets/sliver.dart': Failed assertion: line 1059 pos 14: '_childElements.containsKey(index)': is not true.

`import 'package:flutter/material.dart';
import 'dart:math';
import 'package:cloud_firestore/cloud_firestore.dart';

class FireStoreForm extends StatefulWidget {
@OverRide
FireStoreFormState createState() {
return FireStoreFormState();
}
}

class FireStoreFormState extends State {
final db = Firestore.instance;
final _formKey = GlobalKey();
String age;
String name;
String id;

TextFormField nameField() {
return TextFormField(
decoration: InputDecoration(
// border: InputBorder.none,
hintText: 'name',
// fillColor: Colors.grey[300],
filled: true,
),
validator: (value) {
if (value.isEmpty) {
return 'Please enter some text';
}
},
onSaved: (value) => {name = value, callback(name), print(name)},
);
}

TextFormField ageField() {
return TextFormField(
decoration: InputDecoration(
// border: InputBorder.none,
hintText: 'age',
// fillColor: Colors.grey[300],
filled: true,
),
validator: (value) {
if (value.isEmpty) {
return 'Please enter some text';
}
},
onSaved: (value) => {age = value, callback(age), print(age)},
);
}

@OverRide
Widget build(BuildContext context) {
return Form(
key: _formKey,
child: Column(
mainAxisSize: MainAxisSize.min,
children: [
TextFormField(
decoration: InputDecoration(
// border: InputBorder.none,
hintText: 'name',
// fillColor: Colors.grey[300],
filled: true,
),
validator: (value) {
if (value.isEmpty) {
return 'no value';
} else {
return 'value';
}
},
onSaved: (value) => {
name = value
}
),
SizedBox(height: 16.0),
// ageField(),
// SizedBox(height: 16.0),
],
),
);
}

String callback(value) {
return value;
}

createData() async {
if (_formKey.currentState.validate()) {
_formKey.currentState.save();
DocumentReference ref = await db
.collection('CRUD')
.add({'name': '$name 😎', 'age': '$age', 'todo': randomTodo()});
setState(() => id = ref.documentID);
print(ref.documentID);
}
}

void readData() async {
DocumentSnapshot snapshot = await db.collection('CRUD').document(id).get();
print(snapshot.data);
}

void updateData(DocumentSnapshot doc) async {
await db
.collection('CRUD')
.document(doc.documentID)
.updateData({'todo': randomTodo()});
}

void deleteData(DocumentSnapshot doc) async {
await db.collection('CRUD').document(doc.documentID).delete();
setState(() => id = null);
}

String randomTodo() {
final randomNumber = Random().nextInt(4);
String todo;
switch (randomNumber) {
case 1:
todo = 'Like and subscribe 💩';
break;
case 2:
todo = 'Twitter @RobertBrunhage 🤣';
break;
case 3:
todo = 'Patreon in the description 🤗';
break;
default:
todo = 'Leave a comment 🤓';
break;
}
return todo;
}
}
`

`
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'firestore_form.dart';

class FirestoreCRUDPage extends StatefulWidget {
@OverRide
FirestoreCRUDPageState createState() {
return FirestoreCRUDPageState();
}
}

class FirestoreCRUDPageState extends State {

Card buildItem(DocumentSnapshot doc) {
return Card(
child: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(
'name: ${doc.data['name']}',
style: TextStyle(fontSize: 24),
),
Text(
'name: ${doc.data['age']}',
style: TextStyle(fontSize: 24),
),
Text(
'todo: ${doc.data['todo']}',
style: TextStyle(fontSize: 20),
),
SizedBox(height: 12),
Row(
mainAxisAlignment: MainAxisAlignment.end,
children: [
FlatButton(
onPressed: () => FireStoreFormState().updateData(doc),
child: Text('Update todo',
style: TextStyle(color: Colors.white)),
color: Colors.green,
),
SizedBox(width: 8),
FlatButton(
onPressed: () => FireStoreFormState().deleteData(doc),
child: Text('Delete'),
),
],
)
],
),
),
);
}

@OverRide
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Firestore CRUD'),
),
body: ListView(
padding: EdgeInsets.all(8),
children: [
FireStoreForm(),
SizedBox(
height: 16.0,
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
RaisedButton(
onPressed: FireStoreFormState().createData,
child: Text('Create', style: TextStyle(color: Colors.white)),
color: Colors.green,
),
RaisedButton(
onPressed: FireStoreFormState().id != null ? FireStoreFormState().readData : null,
child: Text('Read', style: TextStyle(color: Colors.white)),
color: Colors.blue,
),
],
),
SizedBox(
height: 16.0,
),
StreamBuilder(
stream: FireStoreFormState().db.collection('CRUD').snapshots(),
builder: (context, snapshot) {
if (snapshot.data.documents.length == 0) {
return Text('No Data');
} else {
return Column(
children: snapshot.data.documents
.map((doc) => buildItem(doc))
.toList());
}
},
)
],
),
);
}
}
`

[VERBOSE-2:ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The method 'validate' was called on null.
Receiver: nul

I have googled, most of the post said Wrap with Form, and add the global form key, but I have added, still not working...

Thanks very much for your time