Question 240358 in Flutter Question posted in
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Flutter / Builder shouldn't return null

I have an issue in my builder causing the following error juste after the builder in my match_page.dart :
"The body might complete normally, causing ‘null’ to be returned, but the return type, ‘Widget’, is a potentially non-nullable type.
Try adding either a return or a throw statement at the end."

The code in the main page:

import 'package:firebase_auth/firebase_auth.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:love_app/components/models/user.dart';
import 'package:love_app/components/repository/userRepository.dart';
import 'package:love_app/controllers/profile_controller.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:get/get.dart';


class MainPage extends StatelessWidget {
  const MainPage({super.key});
  void signUserOut(){
    FirebaseAuth.instance.signOut();
  }

  @override
  Widget build(BuildContext context) {

    final controller = Get.put(ProfileController());
    return Scaffold(
      body: SingleChildScrollView(
        child: FutureBuilder<List<UserModel>>(
          future: controller.getAllUser(),
          builder: (context, snapshot) {
            if(snapshot.connectionState == ConnectionState.done){
              if(snapshot.hasData){

              // UserModel userData = snapshot.data as UserModel;

                return GridView.count(
                crossAxisCount: 2,
                children: List.generate(snapshot.data!.length, (index) {
                return Center(
                    child: Column(
                        children: [
                           Center(
                            child: Container(
                            padding: const EdgeInsets.all(8),
                            decoration: BoxDecoration(
                              color: Colors.black.withOpacity(0.04),
                              borderRadius: const BorderRadius.all(Radius.circular(16)),
                              
                            ),
                            height: 185,
                            width: 185,
                            margin:EdgeInsets.all(5.0)
                          ),
                          ),
                          
                          Stack(
                            children: [
                                ListTile(
                                  iconColor: Colors.blue,
                                  tileColor: Colors.blue.withOpacity(0.1),
                                  title: Text("Pseudo: ${snapshot.data![index].pseudo}"),
                                  subtitle: Column(crossAxisAlignment: CrossAxisAlignment.start,
                                  children: [Text("Nom: ${snapshot.data![index].nom}"),
                                  Text("Prénom: ${snapshot.data![index].prenom}"),
                                  Text("Description: ${snapshot.data![index].description}"),
                                  Text("Passions: ${snapshot.data![index].passions}")
                                  ]
                                )
                              )   ],
                          )
                          
                        ],),
                    
                  );
                }
            ),
          );
  }
  else if (snapshot.hasError) {
  print("Snapshot data: ${snapshot.data}");
  return const SizedBox(
  width: 200.0,
  height: 300.0,
  child: Card(child: Text('Passe dans else du erreur!')),
);}
else { 
  print("Snapshot data: ${snapshot.data}");
  return const SizedBox(
  width: 200.0,
  height: 300.0,
  child: Card(child: Text('Passe dans else du has data!')));}}})));}}

To find the informations from the user which are in my collection "Utilisateur" from Firestore I use the userRepository.dart :

import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:firebase_storage/firebase_storage.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:love_app/components/models/user.dart';

class UserRepository extends GetxController {
  static UserRepository get instance => Get.find();

  final _db = FirebaseFirestore.instance;

Future<UserModel> getUserDetails(String id) async {
  final snapshot = await _db.collection("Utilisateur").where("id", isEqualTo: id).get();
  final userData = snapshot.docs.map((e) => UserModel.fromSnapshot(e)).single;
  return userData;
}

Future<List<UserModel>> allUser() async {
  final snapshot = await _db.collection("Utilisateur").get();
  final userData = snapshot.docs.map((e) => UserModel.fromSnapshot(e)).toList();
  return userData;
}

}

And I Use also this profile_controller.dart:

import 'package:get/get.dart';
import 'package:love_app/components/repository/userRepository.dart';
import 'package:love_app/components/models/user.dart';

class ProfileController extends GetxController {
  static ProfileController get instance => Get.find();

  final _userRepo = Get.put(UserRepository());

Future<UserModel> getUserData() {
    const id = "9uVSkDP4Twqh0FWCekXV";
    // TODo: essayer de récupérer l'id du user connecté
    return _userRepo.getUserDetails(id);

  }


Future<List<UserModel>> getAllUser() async {
  return await _userRepo.allUser();
}
}

My user.dart:

import 'package:cloud_firestore/cloud_firestore.dart';

class UserModel {

  final String id;
  final String description;
  final String nom;
  final String passions;
  final String prenom;
  final String pseudo;

  const UserModel({
    required this.id, 
    required this.description, 
    required this.nom, 
    required this.passions, 
    required this.prenom, 
    required this.pseudo, 

 toJson() {
  return { "Description" : description, "Nom": nom, "Passions": passions,
  "Prenom": prenom , "Pseudo": pseudo};
 }

factory UserModel.fromSnapshot(DocumentSnapshot<Map<String, dynamic>> document) {
  final data = document.data()!;
  return UserModel (
    id: document.id,
    description: data['Description'],
    nom: data['Nom'],
    passions: data['Passions'],
    prenom: data['Prenom'],
    pseudo: data['Pseudo'],
  );
}

}

All of these functions has a return so I can’t identify where is the problem.
Could you please help me to resolve it?

Tags:

3

Answers


  1. Chosen as BEST ANSWER
    0

    The else if and else conditions are at the end of the code like this:

      else if (snapshot.hasError) {   print("Snapshot data: ${snapshot.data}");   return const SizedBox(   width: 200.0,   height:
300.0,   child: Card(child: Text('Passe dans else du erreur!')), );}

else {    print("Snapshot data: ${snapshot.data}");   return const SizedBox(   width: 200.0,   height: 300.0,   child: Card(child: Text('Passe dans else du has data!')));}}})));}}

    These conditions are supplying all the conditions, no? If the snapshot has a data, else if there is an error or else if any other conditions are met.


  2. 0

    I guess it happens because of your first if in your builder.

    You only return a widget if your
    if(snapshot.connectionState == ConnectionState.done)
    condition is true. But if not, you do nothing. Return a widget if the connection state is not done.

    Login or Signup to reply.
  3. 0

    As Ozan answered, your builder method only returns a widget when the data has successfully loaded, but it always needs to return a widget – even when those conditions have not been met.

    My common way of implementing builder:

    builder: (context, snapshot) {
  if(snapshot.hasError) return Text("ERROR: ${snapshot.error}");
  if(!snapshot.hasData) return CircularProgressIndicator();

  return GridView.count(
    ...
  )
}
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