，伙计们，我需要您的帮助，我正在按照一个Udemy教程“使用Reed的Flutter构建社交网络应用程序”，但是我有一个小问题。当我运行我的应用程序时，它一直告诉我getter键是在null上调用的。我已经与这个错误作斗争了两天。请帮忙。下面是我的代码。
控制台错误：
(27685): 0
D/GraphicBuffer(27685): register, handle(0x97a46580) (w:480 h:960 s:480 f:0x1 u:f02)
D/GraphicBuffer(27685): register, handle(0x95465580) (w:480 h:960 s:480 f:0x1 u:f02)
D/GraphicBuffer(27685): register, handle(0x954657c0) (w:480 h:888 s:480 f:0x1 u:f02)
I/flutter (27685): ══╡ EXCEPTION CAUGHT BY RENDERING LIBRARY ╞═════════════════════════════════════════════════════════
I/flutter (27685): The following NoSuchMethodError was thrown during performLayout():
I/flutter (27685): The getter 'key' was called on null.
I/flutter (27685): Receiver: null
I/flutter (27685): Tried calling: key
I/flutter (27685):
I/flutter (27685): The relevant error-causing widget was:
I/flutter (27685): ListView file:///C:/Users/DELL/Documents/fluttershare/fluttershare/lib/pages/profile.dart:284:12
I/flutter (27685):
I/flutter (27685): When the exception was thrown, this was the stack:
I/flutter (27685): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
I/flutter (27685): #1 SliverChildListDelegate.build (package:flutter/src/widgets/sliver.dart:676:27)
主页上的个人资料页面类
Profile(profileId:currentUser?.id),
个人资料页面本身
import 'package:cached_network_image/cached_network_image.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:flutter_svg/svg.dart';
import 'package:fluttershare/models/user.dart';
import 'package:fluttershare/pages/edit_profile.dart';
import 'package:fluttershare/pages/home.dart';
import 'package:fluttershare/widgets/header.dart';
import 'package:fluttershare/widgets/post.dart';
import 'package:fluttershare/widgets/post_tile.dart';
import 'package:fluttershare/widgets/progress.dart';
class Profile extends StatefulWidget {
final String profileId;
Profile({this.profileId});
@override
_ProfileState createState() => _ProfileState();
}
class _ProfileState extends State<Profile> {
String postOrientation ="grid";
bool isloading=false;
final String currentUserid=currentUser?.id;
int postCount=0;
List<Post>posts=[];
@override
void initState() {
super.initState();
getProfilePost();
}
getProfilePost()async{
setState(() {
isloading=true;
});
QuerySnapshot snapshot=await postRef.document( widget.profileId)
.collection("userPosts")
.orderBy("timestamp",descending: true).getDocuments();
setState(() {
isloading=false;
postCount=snapshot.documents.length;
posts= snapshot.documents.map((doc)=>Post.fromDocument(doc)).toList();
});
}
Column buildCountColumn(String label, int count){
return Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
count.toString(),
style: TextStyle(fontSize: 22.0, fontWeight: FontWeight.bold),
),
Container(
margin:EdgeInsets.only(top: 4.0),
child: Text(
label,
style: TextStyle(
color: Colors.grey,
fontSize: 15.0,
fontWeight: FontWeight.w400
),
),
)
],
);
}
editProfile(){
Navigator.push(context, MaterialPageRoute(builder: (context)=>
EditProfile(currentUserId:currentUserid)));
}
Container buildButton({String text, Function function}){
return Container(
padding: EdgeInsets.only(top: 2.0),
child: FlatButton(
onPressed: function,
child: Container(
width: 250.0,
height: 27.0,
alignment: Alignment.center,
child: Text(text, style: TextStyle(color: Colors.white,
fontWeight: FontWeight.bold),),
decoration: BoxDecoration(
color: Colors.blue,
border: Border.all(
color: Colors.blue,
),
borderRadius: BorderRadius.circular(5.0),
),
)),
);
}
buildProfileButton(){
//for viewing your own profile-show edit profile button
bool isProfileOwner=currentUserid==widget.profileId;
if(isProfileOwner){
return buildButton(
text: "Edit Profile",
function: editProfile,
);
}
}
buildProfileHeader(){
FutureBuilder(
future: userRef.document(widget.profileId).get(),
builder: (context, snapshot){
if(!snapshot.hasData){
return circularProgress();
}
User user= User.fromDocument(snapshot.data);
return Padding(
padding: EdgeInsets.all(16.0),
child: Column(
children: <Widget>[
Row(
children: <Widget>[
CircleAvatar(
radius: 40.0,
backgroundColor: Colors.grey,
backgroundImage: CachedNetworkImageProvider(user.photoUrl),
),
Expanded(
flex: 1,
child: Column(
children: <Widget>[
Row(mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
buildCountColumn("posts",postCount),
buildCountColumn("followers",0),
buildCountColumn("following",0),
],
),
Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
buildProfileButton(),
],
)
],
)
)
],
),
Container(
alignment: Alignment.centerLeft,
padding: EdgeInsets.only(top: 12.0),
child: Text(user.username, style: TextStyle(
color: Colors.grey, fontWeight: FontWeight.bold, fontSize: 15.0),
),
),
Container(
alignment: Alignment.centerLeft,
padding: EdgeInsets.only(top: 4.0),
child: Text(user.displayName, style: TextStyle(
color: Colors.grey, fontWeight: FontWeight.bold,),
),
),
Container(
alignment: Alignment.centerLeft,
padding: EdgeInsets.only(top: 2.0),
child: Text(user.bio,style: TextStyle(fontStyle: FontStyle.normal),
),
)
],
),
);
});
}
setPostOrientation(String postOrientation){
this.postOrientation=postOrientation;
}
buildProfilePost(){
if(isloading){
return circularProgress();
}
else if(posts.isEmpty){
return Container(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
SvgPicture.asset(
"assets/images/no_content.svg",
height: 260.0,
),
Padding(
padding: EdgeInsets.only(top: 20.0),
child: Text(
"No Posts",
style: TextStyle(color: Colors.redAccent, fontSize: 40.0, fontWeight: FontWeight.bold),
),
)
],
),
);
}
else if(postOrientation=="grid"){
List<GridTile>gridTiles=[];
posts.forEach((post){
gridTiles.add(GridTile(child:PostTile(post)));
});
return GridView.count(
crossAxisCount: 3,
childAspectRatio: 1,
mainAxisSpacing: 1.5,
crossAxisSpacing: 1.5,
shrinkWrap: true,
physics: NeverScrollableScrollPhysics(),
children: gridTiles,
);
} else if(postOrientation=="list"){
return Column(
children:posts ,
);
}
}
buildTogglePostOrientation(){
return Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
IconButton(
onPressed: ()=>setPostOrientation("grid"),
icon: Icon(Icons.grid_on,
color: postOrientation=="grid"
?Theme.of(context).primaryColor:Colors.grey,)
),
IconButton(
icon: Icon(Icons.list,
color: postOrientation=="list"
?Theme.of(context).primaryColor:Colors.grey,),
onPressed: ()=>setPostOrientation("list"),)
],
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: header(context,titleText: "Profile"),
body:ListView(
children: <Widget>[
buildProfileHeader(),
Divider(),
buildTogglePostOrientation(),
Divider(
height: 0.0,
),
buildProfilePost(),
],
)
);
}
}
错误指向此处的列表视图
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: header(context,titleText: "Profile"),
body:ListView(
children: <Widget>[
buildProfileHeader(),
Divider(),
buildTogglePostOrientation(),
Divider(
height: 0.0,
),
buildProfilePost(),
],
)
);
}
}
请帮助