所以我正在創建一個聊天應用程式。我需要通過提及他們的用戶名和電子郵件來顯示 firebase 中所有用戶的串列。我在第 56 行收到上述錯誤。另外，如果我洗掉該行中的空檢查運算子
QuerySnapshot <Map<String, dynamic>>? searchResultSnapshot;
并且在開始時更換遲到會產生遲到的初始化錯誤。
import 'package:chatapp/services/database.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
class Search extends StatefulWidget {
_Search createState() => _Search();
}
class _Search extends State<Search> {
QuerySnapshot <Map<String, dynamic>>? searchResultSnapshot;
bool isLoading = false;
bool haveUserSearched = false;
DatabaseMethods databaseMethods = new DatabaseMethods();
var searchEditingController = TextEditingController();
InitiateSearch() async {
if (searchEditingController.text.isNotEmpty) {
setState(() {
isLoading = true;
});
await databaseMethods.GetUserByUsername(searchEditingController.text)
.then((snapshot) {
searchResultSnapshot = snapshot;
print("$searchResultSnapshot");
setState(() {
isLoading = false;
haveUserSearched = true;
});
});
}
}
Widget UserList() {
return Container(
height: 500,
child: ListView.builder(
itemCount: searchResultSnapshot?.docs.length,
itemBuilder: (context, index) {
return UserTile(
searchResultSnapshot?.docs[index].data()["userName"],
searchResultSnapshot?.docs[index].data()["userEmail"],
);
}),
);
}
Widget UserTile(String? userName, String? userEmail) {
return Container(
padding: EdgeInsets.symmetric(horizontal: 24, vertical: 16),
child: Row(
children: [
Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(
userName!, //error here
style: TextStyle(color: Colors.white, fontSize: 16),
),
Text(
userEmail!,
style: TextStyle(color: Colors.white, fontSize: 16),
)
],
),
Spacer(),
GestureDetector(
onTap: () {
null;
},
child: Container(
padding: EdgeInsets.symmetric(horizontal: 12, vertical: 8),
decoration: BoxDecoration(
color: Colors.blue, borderRadius: BorderRadius.circular(24)),
child: Text(
"Message",
style: TextStyle(color: Colors.white, fontSize: 16),
),
),
)
],
),
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
titleSpacing: 0,
leading: Builder(
builder: (BuildContext context) {
return IconButton(
icon: const Icon(
Icons.arrow_back_ios,
color: Colors.white,
),
onPressed: () {
Navigator.pop(context);
});
},
),
title: Text('Search'),
),
body: Padding(
padding: const EdgeInsets.all(15.0),
child: Column(
children: [
Container(
height: 36,
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.all(Radius.circular(10)),
boxShadow: [
BoxShadow(
color: Colors.black,
),
BoxShadow(
color: Colors.black,
spreadRadius: -12.0,
blurRadius: 12.0,
),
],
),
margin: EdgeInsets.symmetric(horizontal: 10.0, vertical: 8.0),
child: Padding(
padding:
const EdgeInsets.symmetric(vertical: 0, horizontal: 10.0),
child: TextFormField(
style: TextStyle(color: Colors.black),
controller: searchEditingController,
decoration: InputDecoration(
border: InputBorder.none,
hintText: 'Search',
hintStyle: TextStyle(color: Colors.grey),
icon: GestureDetector(
onTap: () {
InitiateSearch();
},
child: Icon(
Icons.search,
color: Colors.grey,
),
),
suffixIcon: IconButton(
onPressed: searchEditingController.clear,
icon: Icon(
Icons.cancel_rounded,
color: Colors.grey,
),
),
),
),
),
), //Search
SizedBox(
height: 12,
),
UserList(),
],
),
));
}
}
這是我的資料庫檔案。
import 'package:cloud_firestore/cloud_firestore.dart';
class DatabaseMethods {
GetUserByUsername(String username) async {
return await
FirebaseFirestore.instance
.collection('users')
.get()
.then((QuerySnapshot querySnapshot) {
querySnapshot.docs.forEach((doc) {
print(doc["userName"]);
});
});
}
Future<void> UploadUserInfo(userData) async {
FirebaseFirestore.instance.collection("users").add(userData).catchError((e) {
print(e.toString());
});
}
}
我真的很感謝你在這方面的幫助。
uj5u.com熱心網友回復：
您可以替換下面的代碼
children: [
Text(
userName!, //error here
style: TextStyle(color: Colors.white, fontSize: 16),
),
Text(
userEmail!,
style: TextStyle(color: Colors.white, fontSize: 16),
)
],
和
children: [
Text(
userName ?? "", //error here
style: TextStyle(color: Colors.white, fontSize: 16),
),
Text(
userEmail ?? "",
style: TextStyle(color: Colors.white, fontSize: 16),
)
],
uj5u.com熱心網友回復：
代替
return UserTile(
searchResultSnapshot?.docs[index].data()["userName"],
searchResultSnapshot?.docs[index].data()["userEmail"],
);
用這個
return UserTile(
searchResultSnapshot?.docs[index].data()["userName"]??"",
searchResultSnapshot?.docs[index].data()["userEmail"]??"",
);
并替換字串？帶有字串（洗掉？）
Widget UserTile(String userName, String userEmail)
并使用如下值
Text(userName,style: TextStyle(color: Colors.white, fontSize: 16),),
轉載請註明出處，本文鏈接：https://www.uj5u.com/qiye/479412.html