方法 'data' 在 null 上调用。接收器：空 尝试在颤振火碱聊天应用程序中调用：data()

Question

在构建FutureBuilder<文档快照<映射<字符串，动态>gt>(dirty，state:_FutureBuilderState<DocumentSnapshot<Map<String，dynamic>>#c2b0e(：对null调用了方法"data"。接收方：空尝试调用：data((

聊天应用程序中的：-此处突出显示源代码

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:jobkar/public/model/user_model.dart';
import 'package:jobkar/public/view/navigation/message/chat_room.dart';
class Message extends StatefulWidget {
const Message({Key? key}) : super(key: key);
@override
State<Message> createState() => _MessageState();
}
class _MessageState extends State<Message> {
final currentUser = FirebaseAuth.instance.currentUser;
final searchController = TextEditingController();
String search = '';
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.grey[300],
body: Column(
children: [
Padding(
padding: const EdgeInsets.all(8.0),
child: Container(
height: 50,
width: double.infinity,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(10), color: Colors.white),
child: Row(
children: [
Flexible(
child: TextFormField(
controller: searchController,
onChanged: (value) {
search = value;
},
decoration: InputDecoration(
hintText: 'Search person',
border: InputBorder.none,
prefixIcon: const Icon(
Icons.dehaze,
size: 26,
color: Colors.black54,
),
hintStyle: GoogleFonts.raleway(
fontSize: 16, fontWeight: FontWeight.normal)),
),
),
Padding(
padding: const EdgeInsets.all(5.0),
child: Container(
height: 40,
width: 40,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(8),
color: Colors.black54),
child: Center(
child: IconButton(
onPressed: () {
setState(() {});
},
icon: const Icon(
Icons.search,
color: Colors.white,
),
),
),
),
),
],
),
),
),
Expanded(
child: StreamBuilder(
stream: FirebaseFirestore.instance
.collection('users')
.doc(currentUser!.uid)
.collection('message')
.snapshots(),
builder: (BuildContext context, AsyncSnapshot snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return Center(
child: CircularProgressIndicator(
color: Colors.blue[900],
),
);
} else if (snapshot.hasError) {
return const Center(
child: Text("Something went wrong please try later"),
);
} else if (snapshot.hasData) {
return ListView.builder(
itemCount: snapshot.data!.docs.length,
itemBuilder: (context, index) {
var friendId = snapshot.data!.docs[index].id;
var lastMessage = snapshot.data!.docs[index]['lastMessage'];
return FutureBuilder(
future: FirebaseFirestore.instance.collection('users').doc(friendId).get(),
builder: (BuildContext context , AsyncSnapshot snapshot) {
**final userModel = UserModel.fromMap(snapshot.data.data() as Map<String,dynamic>);**
if (snapshot.hasData) {
var friend = snapshot.data;
if (search.isEmpty) {
return ListTile(
onTap: () {
Navigator.push(context,
MaterialPageRoute(builder: (context) =>
ChatRoom(
userModel: userModel,
friendName: friend['name'],
friendImage: friend['imageUrl'],
friendId: friend['uid'],
friendEmail: friend['email']
),
),
);
},
title: Text(
friend['name'],
style: GoogleFonts.raleway(
fontWeight: FontWeight.normal),
),
subtitle: Text(lastMessage,
overflow: TextOverflow.ellipsis,
style: GoogleFonts.raleway(
fontWeight: FontWeight.normal),
),
leading: Container(
height: 45,
width: 45,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(15.0),
color: Colors.white),
child: const Center(
child: Icon(Icons.person),
),
),
);
} else if (friend['name']
.toString()
.toLowerCase()
.startsWith(search.toLowerCase()) ||
friend['name']
.toString()
.toUpperCase()
.startsWith(search.toUpperCase())) {
return ListTile(
onTap: () {
Navigator.push(context,
MaterialPageRoute(builder: (context) =>
ChatRoom(
userModel: userModel,
friendName: friend['name'],
friendImage: friend['imageUrl'],
friendId: friend['uid'],
friendEmail: friend['email']
),
),
);
},
title: Text(
friend['name'],
style: GoogleFonts.raleway(
fontWeight: FontWeight.normal),
),
subtitle: Text(lastMessage,
style: GoogleFonts.raleway(
fontWeight: FontWeight.normal),
),
leading: Container(
height: 45,
width: 45,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(15.0),
color: Colors.white),
child: const Center(
child: Icon(Icons.person),
),
),
);
}
return Container();
}
return Container();
}
);
});
}
return Container();
},
),
),
],
),
);
}
}

Answer 1

获取等数据后生成模型

builder: (BuildContext context , AsyncSnapshot snapshot) {
if (snapshot.hasData) {
final mapData = snapshot.data.data() as Map?;
if(mapData == null) return Text("Got null data");
final userModel = UserModel.fromMap(mapData);
var friend = snapshot.data;