Unhandled Exception: NoSuchMethodError: The method 'split' was called on null - firebase

Question

This is a simple contact app that allows to add view and edit contact details of individuals. The error here can't be totally understood by me.
class ViewContact extends StatefulWidget {
final String id;
ViewContact(this.id);
#override
_ViewContactState createState() => _ViewContactState(this.id);
}
class _ViewContactState extends State<ViewContact> {
DatabaseReference _databaseReference = FirebaseDatabase.instance.reference();
String mascot = "https://learncodeonline.in/mascot.png";
String id;
_ViewContactState(id);
Contact _contact;
bool isLoading = true;
getContact(id) async {
_databaseReference.child(id).onValue.listen ((event){
setState(() {
print(event.snapshot);
_contact = Contact.fromSnapshot(event.snapshot);
isLoading = false;
print(_contact.lastName);
});
});
}
#override
void initState(){
super.initState();
this.getContact(id);
}
callAction(String number) async{
String url = 'tel: $number';
if (await canLaunch(url)){
await launch(url);
}
else {
throw 'Could call $number';
}
}
smsAction(String number) async{
String url ='sms: $number';
if (await canLaunch(url)){
await launch(url);
}
else {
throw 'lol';
}
}
navigateToLastScreen(){
Navigator.pop(context);
}
navigateToEditScreen(id){
Navigator.push(context, MaterialPageRoute(builder: (context){
return EditContact();
}));
}
The error shown is below. Can the error be because of the id variable? (Pretty new towards Flutter).
[ERROR:flutter/lib/ui/ui_dart_state.cc(148)] Unhandled Exception: NoSuchMethodError: The method 'split' was called on null.
E/flutter (12369): Receiver: null
E/flutter (12369): Tried calling: split("/")
E/flutter (12369): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:50:5)
E/flutter (12369): #1 DatabaseReference.child (package:firebase_database/src/database_reference.dart:24:58)
E/flutter (12369): #2 _ViewContactState.getContact (package:firebase_authentication/screens/view_contact.dart:24:25)
E/flutter (12369): <asynchronous suspension>
E/flutter (12369): #3 _ViewContactState.initState (package:firebase_authentication/screens/view_contact.dart:36:10)
E/flutter (12369): #4 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4033:58)
E/flutter (12369): #5 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3902:5)
E/flutter (12369): #6 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #7 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #8 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5092:14)
E/flutter (12369): #9 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #10 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #11 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3935:16)
E/flutter (12369): #12 Element.rebuild (package:flutter/src/widgets/framework.dart:3721:5)
E/flutter (12369): #13 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3907:5)
E/flutter (12369): #14 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3902:5)
E/flutter (12369): #15 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #16 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #17 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5092:14)
E/flutter (12369): #18 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #19 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #20 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5092:14)
E/flutter (12369): #21 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #22 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #23 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5092:14)
E/flutter (12369): #24 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #25 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #26 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:5092:14)
E/flutter (12369): #27 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #28 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #29 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3935:16)
E/flutter (12369): #30 Element.rebuild (package:flutter/src/widgets/framework.dart:3721:5)
E/flutter (12369): #31 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3907:5)
E/flutter (12369): #32 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4053:11)
E/flutter (12369): #33 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3902:5)
E/flutter (12369): #34 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #35 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #36 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3935:16)
E/flutter (12369): #37 Element.rebuild (package:flutter/src/widgets/framework.dart:3721:5)
E/flutter (12369): #38 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3907:5)
E/flutter (12369): #39 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3902:5)
E/flutter (12369): #40 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3084:14)
E/flutter (12369): #41 Element.updateChild (package:flutter/src/widgets/framework.dart:2887:12)
E/flutter (12369): #42 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3935:16)
E/flutter (12369): #43 Element.rebuild (package:flutter/src/widgets/framework.dart:3721:5)
E/flutter (12369): #44 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart
this is the stack over flow error i am facing. Well same as the previous error , i can't figure out this one too :(
I/flutter ( 4594): The following StackOverflowError was thrown building ViewContact(dirty, state:
I/flutter ( 4594): _ViewContactState#4e21c):
I/flutter ( 4594): Stack Overflow
I/flutter ( 4594):
I/flutter ( 4594): When the exception was thrown, this was the stack:
I/flutter ( 4594): #0 Contact.email (package:firebase_authentication/model/contact.dart:25:4)
I/flutter ( 4594): #1 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #2 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #3 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #4 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #5 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #6 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #7 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #8 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #9 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #10 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #11 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #12 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #13 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #14 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #15 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #16 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #17 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #18 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #19 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #20 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #21 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #22 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #23 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #24 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #25 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #26 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #27 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #28 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #29 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #30 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #31 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #32 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #33 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #34 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #35 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #36 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #37 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #38 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #39 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #40 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #41 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #42 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #43 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): ...
I/flutter ( 4594): ...
I/flutter ( 4594): #59478 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59479 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59480 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59481 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59482 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59483 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59484 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59485 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59486 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59487 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59488 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59489 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59490 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59491 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59492 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59493 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59494 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59495 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59496 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59497 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59498 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59499 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59500 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59501 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59502 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59503 Contact.email (package:firebase_authentication/model/contact.dart:25:29)
I/flutter ( 4594): #59504 _ViewContactState.build (package:firebase_authentication/screens/view_contact.dart:179:40)
I/flutter ( 4594): #59505 StatefulElement.build (package:flutter/src/widgets/framework.dart:4012:27)
I/flutter ( 4594): #59506 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3924:15)
I/flutter ( 4594): #59507 Element.rebuild (package:flutter/src/widgets/framework.dart:3721:5)
I/flutter ( 4594): #59508 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2340:33)
I/flutter ( 4594): #59509 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:700:20)
I/flutter ( 4594): #59510 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&SemanticsBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:285:5)
I/flutter ( 4594): #59511 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1016:15)
I/flutter ( 4594): #59512 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:958:9)
I/flutter ( 4594): #59513 _WidgetsFlutterBinding&BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:874:5)
I/flutter ( 4594): #59517 _invoke (dart:ui/hooks.dart:236:10)
I/flutter ( 4594): #59518 _drawFrame (dart:ui/hooks.dart:194:3)
I/flutter ( 4594): (elided 3 frames from package dart:async)
================================================================================
This is the Widget Associated with the View Contact state.
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text("Add Contact"),
centerTitle: true,
leading: IconButton(
icon: Icon(Icons.arrow_back_ios),
onPressed: (){navigateToLastScreen(context);},
),
),
body: Container(
padding: EdgeInsets.all(20.0),
child: ListView(
children: <Widget>[
Container(
margin: EdgeInsets.only(top: 20.0),
child: GestureDetector(
onTap: (){
this.pickImage();
},
child: Center(
child: Container(
width: 130.0,
height: 130.0,
decoration: BoxDecoration(
border: Border.all(color: Colors.white, width: 4.0),
shape: BoxShape.circle,
image: DecorationImage(
fit: BoxFit.fill,
image: _photoUrl=="empty"? NetworkImage("https://i.imgur.com/BoN9kdC.png"): NetworkImage(_photoUrl),
),
),
),
),
),
),
Container(
margin: EdgeInsets.only(top: 40.0),
child: TextField(
onChanged: (value){
setState(() {
_firstName = value;
});
},
decoration: InputDecoration(
labelText: 'First Name',
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10.0),
),
),
),
),
Container(
margin: EdgeInsets.only(top: 20.0),
child: TextField(
onChanged: (value){
setState(() {
_lastName = value;
});
},
decoration: InputDecoration(
labelText: 'Last Name',
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10.0),
),
),
),
),
Container(
margin: EdgeInsets.only(top: 20.0),
child: TextField(
onChanged: (value){
setState(() {
_email = value;
});
},
decoration: InputDecoration(
labelText: 'E-mail',
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10.0),
),
),
),
),
Container(
margin: EdgeInsets.only(top: 20.0),
child: TextField(
onChanged: (value){
setState(() {
_phone = value;
});
},
decoration: InputDecoration(
labelText: 'Phone',
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10.0),
),
),
),
),
Container(
margin: EdgeInsets.only(top: 20.0),
child: TextField(
onChanged: (value){
setState(() {
_address = value;
});
},
decoration: InputDecoration(
labelText: 'Address',
border: OutlineInputBorder(
borderRadius: BorderRadius.circular(10.0),
),
),
),
),
//save the shit
Container(
padding: EdgeInsets.only(top: 20.0),
child: RaisedButton(
color: Colors.teal,
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(20.0)),
padding: EdgeInsets.fromLTRB(50, 10, 50, 10),
onPressed: (){
saveContact(context);
},
child: Text("ADD CONTACT", style: TextStyle(color: Colors.white, fontSize: 20.0, fontWeight: FontWeight.bold),),
),
),
],
),
),
);
}
}

Answer 1

I believe the id is null.
E/flutter (12369): #2 _ViewContactState.getContact (package:firebase_authentication/screens/view_contact.dart:24:25)
Following the stacktrace, this line raises the exception:
_databaseReference.child(id).onValue.listen((event)
E/flutter (12369): #1 DatabaseReference.child (package:firebase_database/src/database_reference.dart:24:58)
from database_reference.dart line 19-25:
/// Gets a DatabaseReference for the location at the specified relative
/// path. The relative path can either be a simple child key (e.g. ‘fred’) or
/// a deeper slash-separated path (e.g. ‘fred/name/first’).
DatabaseReference child(String path) {
return DatabaseReference._(_database,
(List<String>.from(_pathComponents)..addAll(path.split('/'))));
}
path is your id, so I would say the id is null.
E/flutter (12369): Receiver: null
E/flutter (12369): Tried calling: split("/")
You can add assertion to the constructor, if id is null, an error will be thrown and you can then follow the stacktrace to find the broken code.
class ViewContact extends StatefulWidget {
final String id;
const ViewContact({Key key, #required this.id})
: assert(id != null),
super(key: key);
#override
_ViewContactState createState() => _ViewContactState(this.id);
}
EDIT:
#1
change this line:
_ViewContactState(id);
to
_ViewContactState(this.id);
the field id in the state will never be updated!
#2
you can access the id filed from the Widget class by calling widget.id
id will never be changed don't put it to the State constructor.
This should work
import 'package:firebase_database/firebase_database.dart';
import 'package:flutter/material.dart';
class ViewContact extends StatefulWidget {
final String id;
const ViewContact({Key key, #required this.id})
: assert(id != null),
super(key: key);
#override
_ViewContactState createState() => _ViewContactState();
}
class _ViewContactState extends State<ViewContact> {
final DatabaseReference _databaseReference = FirebaseDatabase.instance.reference();
final String mascot = "https://learncodeonline.in/mascot.png";
Contact _contact;
bool isLoading = true;
getContact(id) async {
_databaseReference.child(id).onValue.listen((event) {
setState(() {
print(event.snapshot);
_contact = Contact.fromSnapshot(event.snapshot);
isLoading = false;
print(_contact.lastName);
});
});
}
#override
void initState() {
super.initState();
this.getContact(widget.id);
}
callAction(String number) async {
String url = 'tel: $number';
if (await canLaunch(url)) {
await launch(url);
} else {
throw 'Could call $number';
}
}
smsAction(String number) async {
String url = 'sms: $number';
if (await canLaunch(url)) {
await launch(url);
} else {
throw 'lol';
}
}
navigateToLastScreen() {
Navigator.pop(context);
}
navigateToEditScreen(id) {
Navigator.push(context, MaterialPageRoute(builder: (context) {
return EditContact();
}));
}
}

Answer 2

You should use
_ViewContactState(this.id);
in the constructor, to initialise id. Otherwise it will be null, and hence the error.
However you don't really need to pass it, as the StatefulWidget can access it through the widget. call
class ViewContact extends StatefulWidget {
final String id;
ViewContact(this.id);
#override
_ViewContactState createState() => _ViewContactState();
}
class _ViewContactState extends State<ViewContact> {
DatabaseReference _databaseReference = FirebaseDatabase.instance.reference();
String mascot = "https://learncodeonline.in/mascot.png";
_ViewContactState();
Contact _contact;
bool isLoading = true;
getContact(id) async {
_databaseReference.child(id).onValue.listen ((event){
setState(() {
print(event.snapshot);
_contact = Contact.fromSnapshot(event.snapshot);
isLoading = false;
print(_contact.lastName);
});
});
}
#override
void initState(){
super.initState();
this.getContact(widget.id);
}