问题描述
我对Flutter和Firestore非常陌生。因此，我在Firebase存储上上传了一些照片。 Here is how storage looks
然后，我将其下载URL粘贴到firestore数据库中。 Here is how firestore looks
════════小部件库捕获到异常═══════════════════════════════ ════ 'package：Flutter / src / painting / _network_image_io.dart'：失败的断言：第26行pos 14：'url！= null'：不正确。 相关的引起错误的小部件是 FutureBuilder 但是其他数据正在读取并显示在小部件中。 这是我的代码：
import 'package:Flutter/material.dart';
import 'package:hexcolor/hexcolor.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:dotted_line/dotted_line.dart';
class CourseList extends StatefulWidget {
@override
_CourseListState createState() => _CourseListState();
}
class _CourseListState extends State<CourseList> {
@override
Widget build(BuildContext context) {
return FutureBuilder(
future: FirebaseFirestore.instance
.collection('students')
.doc(FirebaseAuth.instance.currentUser.uid)
.get(),builder: (BuildContext context,snapshot) {
if (snapshot.hasData) {
Map<String,dynamic> documentFields = snapshot.data.data();
return ListView(
shrinkWrap: true,children: [
Column(
crossAxisAlignment: CrossAxisAlignment.start,children: [
Stack(
overflow: Overflow.visible,children: [
Positioned(
// top: 0,child: Padding(
padding: const EdgeInsets.fromLTRB(0,10,0),child: Container(
width: 430,height: 230,decoration: Boxdecoration(
image: decorationImage(
image: Assetimage("assets/hero.png"),fit: BoxFit.cover,),Positioned(
top: 200,left: 20,right: 20,child: Card(
color: Hexcolor('#3B3E43'),elevation: 10,shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10.0),child: Padding(
padding: const EdgeInsets.all(15),child: Column(
children: [
Text(
'Welcome to Class information System',textAlign: TextAlign.center,style: TextStyle(
color: Colors.white,fontFamily: 'ProductSans',fontSize: 16,fontWeight: FontWeight.bold,SizedBox(
height: 10,Text(
'UTM Class Management system offers UTM students a varity of features such as,managing and making real time class schedule,finding class venue with dynamic maps and finding all the lecturers office,phone and email all at one place!',style: TextStyle(
color: Colors.grey[300],fontSize: 11,SizedBox(
height: 15,Column(
children: [
Row(
mainAxisAlignment:
MainAxisAlignment.spaceEvenly,children: [
Image.asset(
'assets/001-school.png',scale: 8,SizedBox(
width: 0,Image.asset(
'assets/002-teacher.png',Image.asset(
'assets/003-calendar.png',],SizedBox(
height: 10,Row(
mainAxisAlignment:
MainAxisAlignment.spaceEvenly,children: [
Text(
'Finding class\nvenue with\ndynamic maps',style: TextStyle(
color: Colors.grey[300],fontSize: 10,Text(
'Finding all the\nlecturers informations\nat one place!',Text(
'Make & Edit\nreal time\nclass schedule',)
],SizedBox(
height: 220,Padding(
padding: const EdgeInsets.fromLTRB(25,child: Text(
'Courses Taken',textAlign: TextAlign.left,style: TextStyle(
color: Hexcolor('#E69405'),fontSize: 18,25,5),child: DottedLine(
direction: Axis.horizontal,lineLength: double.infinity,lineThickness: 1.0,dashLength: 4.0,dashColor: Hexcolor('#707070'),dashRadius: 0.0,dashGapLength: 6.0,dashGapColor: Colors.transparent,dashGapRadius: 0.0,SizedBox(
height: 15,Card(
color: Hexcolor('#3B3E43'),margin: EdgeInsets.fromLTRB(25,20),shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10.0),child: Padding(
padding: const EdgeInsets.all(15),child: ListView(
physics: ClampingScrollPhysics(),shrinkWrap: true,children: [
Row(
children: [
Expanded(
child: Padding(
padding:
const EdgeInsets.fromLTRB(10,child: CircleAvatar(
backgroundImage:
NetworkImage(documentFields['img1']),radius: 28,Expanded(
flex: 4,child: Padding(
padding:
const EdgeInsets.fromLTRB(20,child: RichText(
text: TextSpan(
style: TextStyle(
fontFamily: 'ProductSans',fontSize: 17,text: documentFields['course1'],children: <TextSpan>[
TextSpan(
text:
'\nSection: ${documentFields['section1']}',style: TextStyle(
fontFamily: 'ProductSans',fontSize: 14,color: Colors.grey[400],SizedBox(
height: 15,DottedLine(
direction: Axis.horizontal,dashLength: 10,dashGapLength: 0,Row(
children: [
Expanded(
child: Padding(
padding:
const EdgeInsets.fromLTRB(10,child: CircleAvatar(
child: Image.network(
'${documentFields['img2']}'),text: documentFields['course2'],children: <TextSpan>[
TextSpan(
text:
'\nSection: ${documentFields['section2']}',child: CircleAvatar(
child: Image.network(
'${documentFields['img3']}'),text: documentFields['course3'],children: <TextSpan>[
TextSpan(
text:
'\nSection: ${documentFields['section3']}',child: CircleAvatar(
child: Image.network(
'${documentFields['img4']}'),text: documentFields['course4'],children: <TextSpan>[
TextSpan(
text:
'\nSection: ${documentFields['section4']}',)
],);
}
return Center(child: CircularProgressIndicator());
},);
}
}
任何帮助将不胜感激。谢谢！
解决方法
所以，我终于弄清楚了。如果有人在寻找答案。您所要做的就是，将映像存储在Firebase存储中之后，您必须复制存储位置而不是下载URL，然后将其放入Firestore中。然后使用Firebase图片提供程序包在您的应用中调用
child: ListTile(
leading: CircleAvatar(
radius: 25,backgroundImage: FirebaseImage(coffee.img),),尝试在控制台中打印图像URL，以确保其值。
错误是因为其值为null，所以您可能没有正确写入图像URL的密钥Map密钥。