颤振“imageUrl 被调用为空”

如何解决颤振“imageUrl 被调用为空”

我遇到了“图像 url 被调用为 null”的问题。我已经定义了ImageUrl，但我不知道问题出在哪里。

我在add_contact.dart中添加了future builder，但是问题没有解决。我不知道我应该在哪里使用 future builder。

here is the image

这是我的代码：

home_page.dart

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:pop/widgets/add_contact.dart';
import 'package:pop/widgets/user_item.dart';
import '../providers/user.dart';

import 'package:provider/provider.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    final products = Provider.of<Users>(context).items;
    return Scaffold(
      appBar: AppBar(
        title: Text('Pop'),actions: [
          PopupMenuButton(
            child: Icon(Icons.more_vert,color: Colors.white),itemBuilder: (context) => [
              PopupMenuItem(
                child: Text('add account to chat'),value: 'add',),PopupMenuItem(
                child: Text('logout'),value: 'logout',],onSelected: (val) {
              switch (val) {
                case 'logout':
                  FirebaseAuth.instance.signOut();
                  break;
                case 'add':
                  showModalBottomSheet(
                    context: context,builder: (ctx) => AddContact(),);
                  break;
                default:
              }
            },body: ListView.builder(
        itemCount: products.length,itemBuilder: (ctx,i) => ChangeNotifierProvider.value(
          value: products[i],child: UserButton(
            products[i].imageUrl,products[i].name,products[i].phoneNumber,);
  }
}

user.dart

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:intl_phone_number_input/intl_phone_number_input.dart';

class UserItem with ChangeNotifier {
  final String name;
  final String phoneNumber;
  final String imageUrl;
  UserItem({
    @required this.name,@required this.phoneNumber,@required this.imageUrl,});
}

class Users with ChangeNotifier {
  List<UserItem> _items = [];

  List<UserItem> get items {
    return [..._items];
  }

  Future<void> addItem(String phone) async {
    UserItem newItem;
    await FirebaseFirestore.instance
        .collection('users')
        .where('phone_number',isEqualTo: phone)
        .get()
        .then(
          (QuerySnapshot value) => value.docs.forEach(
            (element) {
              newItem = UserItem(
                name: element['username'],phoneNumber: element['phone_number'],imageUrl: element['image_url'],);
            },);
    _items.add(newItem);
    notifyListeners();
  }
}

add_contact.dart

import 'dart:async';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:intl_phone_number_input/intl_phone_number_input.dart';
import 'package:provider/provider.dart';
import '../providers/user.dart';

class AddContact extends StatefulWidget {
  @override
  _AddContactState createState() => _AddContactState();
}

class _AddContactState extends State<AddContact> {
  PhoneNumber number;
  bool isLoading = false;
  final Stream<DocumentSnapshot> _query = FirebaseFirestore.instance
      .collection('users')
      .doc(FirebaseAuth.instance.currentUser.uid)
      .snapshots();
  @override
  Widget build(BuildContext context) {
    return Form(
      child: Container(
        padding: EdgeInsets.only(
            bottom: MediaQuery.of(context).viewInsets.bottom + 10),child: SingleChildScrollView(
          child: Column(
            // mainAxisAlignment: MainAxisAlignment.center,children: <Widget>[
              StreamBuilder<DocumentSnapshot>(
                stream: _query,builder: (context,snapshot) {
                  if (snapshot.connectionState == ConnectionState.waiting) {
                    return CircularProgressIndicator();
                  }
                  return InternationalPhoneNumberInput(
                    initialValue: PhoneNumber(
                      isoCode: snapshot.data['iso_code'],onInputChanged: (val) {
                      number = val;
                    },);
                },isLoading
                  ? CircularProgressIndicator()
                  : RaisedButton.icon(
                      color: Colors.amber,onPressed: () {
                        FutureBuilder(
                          future: Provider.of<Users>(context,listen: false)
                              .addItem(number.phoneNumber),builder: (ctx,snapshot) {
                            if (snapshot.connectionState ==
                                ConnectionState.waiting) {
                              isLoading = true;
                            }
                            isLoading = false;
                          },);
                        Navigator.of(context).pop();
                      },label: Text('add contact'),icon: Icon(Icons.add),);
  }
}