PhotoURL was called on null error in flutter

Question

In my flutter project, i used CachedNetworkImageProvider, in which i passed photo url, but it is showing me an error, that it is called on null. Can anyone help me please? Check out line 158. If you think, there is nothing wrong in this part, and some other widget is causing the error, (that are made by me), then please tell me, i will provide you that. Please help me. I am new to this thing.

Here's the exception -

The getter 'photoUrl' was called on null.
Receiver: null
Tried calling: photoUrl
The relevant error-causing widget was: 
  Upload file:///C:/Users/Hp/AndroidStudioProjects/social_app/lib/pages/home.dart:117:11

Here's the code -

import 'dart:io';
import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:image_picker/image_picker.dart';
import 'package:social_app/models/users.dart';

class Upload extends StatefulWidget {

  final User currentUser;
  Upload({this.currentUser});

  @override
  _UploadState createState() => _UploadState();
}

class _UploadState extends State<Upload> {

  File file;
  handleTakePhoto() async {
    Navigator.pop(context);
    File file = await ImagePicker.pickImage(source: ImageSource.camera, maxWidth: 960, maxHeight: 675);
    // ImagePicker imagePicker;
    // PickedFile pickedFile = await imagePicker.getImage(source: ImageSource.camera, maxHeight: 675, maxWidth: 960);
    // File file = File(pickedFile.path);
    setState(() {
      this.file = file;
    });
  }

  handleChooseFromGallery() async{
    Navigator.pop(context);
    File file = await ImagePicker.pickImage(source: ImageSource.gallery);
    setState(() {
      this.file = file;
    });
    // ImagePicker imagePicker;
    // PickedFile pickedFile = await imagePicker.getImage(source: ImageSource.gallery);
    // File file = File(pickedFile.path);
    // setState(() {
    //   this.file = file;
    // });
  }

  selectImage(parentContext) {
    return showDialog(
      context: parentContext,
      builder: (context) {
        return SimpleDialog(
          title: Text('Create Post'),
          children: <Widget>[
            SimpleDialogOption(
              child: Text('Click Photo'),
              onPressed: handleTakePhoto,
            ),
            SimpleDialogOption(
              child: Text('Import from Gallery'),
              onPressed: handleChooseFromGallery,
            ),
            SimpleDialogOption(
              child: Text('Cancel'),
              onPressed: () => Navigator.pop(context),
            ),
          ],
        );
      }
    );
  }

  Container buildSplashScreen() {
    return Container(
      color: Colors.black54,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          SvgPicture.asset('assets/images/upload.svg', height: 300.0,),
          Padding(
            padding: EdgeInsets.only(top: 40.0),
            child: RaisedButton(
              padding: EdgeInsets.all(10.0),
              shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(8.0)),
              child: Text(
                'Upload Image',
                style: TextStyle(
                  color: Colors.white,
                  fontSize: 30.0,
                ),
              ),
              color: Colors.blueGrey[600],
              onPressed: () => selectImage(context),
            ),
          ),
        ],
      ),
    );
  }

  clearImage() {
    setState(() {
      file =null;
    });
  }

  Scaffold buildUploadForm() {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.white70,
        leading: IconButton(
          icon: Icon(Icons.arrow_back, color: Colors.black,),
          onPressed: clearImage,
        ),
        title: Center(
          child: Text(
            'Caption Post',
            style: TextStyle(
              color: Colors.black,
            ),
          ),
        ),
        actions: [
          FlatButton(
            onPressed: () => print('Pressed'),
            child: Text(
              'Post',
              style: TextStyle(
                color: Colors.blueAccent,
                fontWeight: FontWeight.bold,
                fontSize: 20.0,
              ),
            ),
          ),
        ],
      ),
      body: ListView(
        children: <Widget>[
          Container(
            height: 220.0,
            width: MediaQuery.of(context).size.width * 0.8,
            child: Center(
              child: AspectRatio(
                aspectRatio: 16/9,
                child: Container(
                  decoration: BoxDecoration(
                    image: DecorationImage(
                      fit: BoxFit.cover,
                      image: FileImage(file),
                    ),
                  ),
                ),
              ),
            ),
          ),
          Padding(
            padding: EdgeInsets.only(top: 10.0),
          ),
          ListTile(
            leading: CircleAvatar(
              backgroundImage: CachedNetworkImageProvider(widget.currentUser.photoUrl),
            ),
            title: Container(
              width: 250.0,
              child: TextField(
                  decoration: InputDecoration(
                  hintText: "Write a caption..",
                    border: InputBorder.none,
                ),
              ),
            ),
          ),
          Divider(

          ),
          ListTile(
            leading: Icon(
              Icons.pin_drop,
              color: Colors.blue,
              size: 36.0,
            ),
            title: Container(
              width: 250.0,
              child: TextField(
                decoration: InputDecoration(
                  hintText: 'Search a location...',
                  border: InputBorder.none,
                ),
              ),
            ),
          ),
          Container(
            width: 200.0,
            height: 100.0,
            alignment: Alignment.center,
            child: RaisedButton.icon(
              label: Text(
                'Use current location...',
                style: TextStyle(
                  color: Colors.white,
                ),
              ),
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(30.0),
              ),
              color: Colors.blue,
              onPressed: () => print('Get user location'),
              icon: Icon(
                Icons.my_location,
                color: Colors.white,
              ),
            ),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return file == null ? SafeArea(
      child: Scaffold(
        backgroundColor: Colors.black45,
        body: buildSplashScreen(),
      ),
    ) : buildUploadForm();
  }
}

home page -

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:google_sign_in/google_sign_in.dart';
import 'package:social_app/pages/activity_feed.dart';
import 'package:social_app/pages/create_account.dart';
import 'package:social_app/pages/profile.dart';
import 'package:social_app/pages/search.dart';
import 'package:social_app/pages/timeline.dart';
import 'package:social_app/pages/upload.dart';
import 'package:social_app/widgets/header.dart';
import 'package:social_app/models/users.dart';

final GoogleSignIn googleSignIn = GoogleSignIn();
final usersRef = FirebaseFirestore.instance.collection('users');
final DateTime timeStamp = DateTime.now();
User currentUser;

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  bool isAuth = false;
  PageController pageController;
  int pageIndex=0;

  @override
  void initState(){
    super.initState();
    pageController = PageController(initialPage: 0);
    googleSignIn.onCurrentUserChanged.listen((account) {
      handleSignIn(account);
    },
    onError: (error) {
      print("Error in signing in : $error");
    });
    googleSignIn.signInSilently(suppressErrors: false).then((account){
      handleSignIn(account);
    }).catchError((error){
      print("Error in signing in : $error");
    });
  }

  handleSignIn(GoogleSignInAccount account) {
    if (account != null) {
      createUserInFirestore();
      setState(() {
        isAuth = true;
      });
    }
    else {
      setState(() {
        isAuth = false;
      });
    }
  }

  createUserInFirestore() async{
    final GoogleSignInAccount user = googleSignIn.currentUser;
    DocumentSnapshot doc = await usersRef.doc(user.id).get();

    if(!doc.exists) {
      final username = await Navigator.push(context, MaterialPageRoute(builder: (context) => CreateAccount()));
      usersRef.doc(user.id).set({
        "id" : user.id,
        "username" : username,
        "photoUrl" : user.photoUrl,
        "email" : user.email,
        "displayName" : user.displayName,
        "bio" : "",
        "timeStamp" : timeStamp,
      });
    }
  }

  @override
  void dispose() {
    pageController.dispose();
    super.dispose();
  }

  login() {
    googleSignIn.signIn();
  }

  logout() {
    googleSignIn.signOut();
  }

  onPageChanged(int pageIndex) {
    setState(() {
      this.pageIndex = pageIndex;
    });
  }

  onTap(int pageIndex) {
    pageController.animateToPage(
      pageIndex,
      duration: Duration(milliseconds: 250),
      curve: Curves.easeInOut,
    );
  }

  Scaffold buildAuthScreen(){
    return Scaffold(
      body: PageView(
        children: <Widget>[
          //Timeline(),
          RaisedButton(
             onPressed: logout,
             child: Text('logout'),
           ),
          Search(),
          Upload(currentUser: currentUser),
          ActivityFeed(),
          Profile(),
        ],
        controller: pageController,
        onPageChanged: onPageChanged,
        physics: NeverScrollableScrollPhysics(),
      ),
      bottomNavigationBar: CupertinoTabBar(
        backgroundColor: Colors.black,
        currentIndex: pageIndex,
        onTap: onTap,
        activeColor: Colors.white,
        items: [
          BottomNavigationBarItem(icon: Icon(Icons.home_filled)),
          BottomNavigationBarItem(icon: Icon(Icons.search)),
          BottomNavigationBarItem(icon: Icon(Icons.add_box_outlined)),
          BottomNavigationBarItem(icon: Icon(Icons.favorite_border)),
          BottomNavigationBarItem(icon: Icon(Icons.account_circle)),
        ],
      ),
    );
    // return RaisedButton(
    //   onPressed: logout,
    //   child: Text('logout'),
    // );
  }

  Scaffold buildUnauthScreen() {
    return Scaffold(
      appBar: header(context, titleText: 'Instagram'),
      backgroundColor: Colors.black,
      body: SafeArea(
        child: Container(
          decoration: BoxDecoration(
            gradient: LinearGradient(
              begin: Alignment.topRight,
              end: Alignment.bottomLeft,
              colors: [
                Theme.of(context).primaryColor,
                Colors.teal.withOpacity(1.0),
                Colors.orange,
              ]
            ),
          ),
          alignment: Alignment.center,
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              Text(
                'Technua',
                style: GoogleFonts.gochiHand(
                  fontSize: 70.0,
                  color: Colors.white,
                ),
              ),
              GestureDetector(
                onTap: login,
                child: Container(
                  height: 60.0,
                  width: 260.0,
                  decoration: BoxDecoration(
                    image: DecorationImage(
                      image: AssetImage('assets/images/google_signin_button.png'),
                      fit: BoxFit.cover,
                    )
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return isAuth ? buildAuthScreen() : buildUnauthScreen();
  }
}

@nvoigt what about the constuctor, in which i have initialized it?? — Shreyansh Sharma, Oct 23 '20 at 17:48
I guess you didn't? Do you have a line where you pass something into your constructor that is not null? — nvoigt, Oct 23 '20 at 17:51
i have edited the question, can you check it, see line no. 117 of the home page. — Shreyansh Sharma, Oct 23 '20 at 18:09
@nvoigt you were right, i just forgot to add these statements in home.dart - doc = await usersRef.doc(user.id).get(); currentUser = User.fromDocument(doc); — Shreyansh Sharma, Oct 23 '20 at 18:16

score 2 · Accepted Answer · answered Oct 23 '20 at 14:57

2

You have created an optional named parameter currentUser in your StatefulWidget Upload. I think the user that you have passed in the Upload widget is null.

You have to check where are you calling the Upload widget from & then check whether the user is null or not.

However, if the currentUser is null, you can prevent the error by using null aware operator as follows:

leading: CircleAvatar(
           backgroundImage: CachedNetworkImageProvider(
                              widget.currentUser?.photoUrl,  // <-----
                            ),
         ),

answered Oct 23 '20 at 14:57

Ravi Singh Lodhi

2,605
1
9
12

is it not initialized by constructor?? – Shreyansh Sharma Oct 23 '20 at 17:50
It is initialized by the constructor with the value that is passed on to it. If you pass `null` as the parameter, then it will initialize `currentUser` with `null`. – Ravi Singh Lodhi Oct 23 '20 at 18:40

score 1 · Answer 2 · answered Oct 23 '20 at 14:45

1

Your current user is null. You have to set a user in here:

    final User currentUser;

answered Oct 23 '20 at 14:45

Akif

7,098
7
27
53

PhotoURL was called on null error in flutter

2 Answers2