为什么Firebase实时数据库的数据在控制台中显示为空？

我正在尝试创建一个简单的应用程序，将帖子添加到 firebase 实时数据库并在 flutter 中的列表视图上显示它们，但是当我将其“发布”到数据库时，在 firebase 控制台上，数据值不断显示为空。有谁知道出了什么问题？

这是我的一些代码 -

飞镖后

class Post {
Image coverImg;
File audioFile;
String body;
String author;
Set usersLiked = {};
DatabaseReference _id;
Post(this.body, this.author);
void likePost(User user) {
if (this.usersLiked.contains(user.uid)) {
this.usersLiked.remove(user.uid);
} else {
this.usersLiked.add(user.uid);
}
}
void update() {
updatePost(this, this._id);
}
void setId(DatabaseReference id) {
this._id = id;
}
Map toJson() {
return {
'body': this.body,
'author': this.author,
'usersLiked': this.usersLiked.toList()
};
}
}
Post createPost(record) {
Map attributes = {
'author': '',
'usersLiked': [],
'body': ''
};
record.forEach((key, value) => {attributes[key] = value});
Post post = new Post(attributes['body'], attributes['author']);
post.usersLiked = new Set.from(attributes['usersLiked']);
return post;
}
class PostList extends StatefulWidget {
final List listItems;
final User user;
PostList(this.listItems, this.user);
@override
_PostListState createState() => _PostListState();
}
class _PostListState extends State {
void like(Function callBack) {
this.setState(() {
callBack();
});
}
@override
void initState() {
super.initState();
}
@override
void dispose() {
super.dispose();
}
@override
Widget build(BuildContext context) {
return ListView.builder(
itemCount: this.widget.listItems.length,
itemBuilder: (context, index) {
var post = this.widget.listItems[index];
return Card(
elevation: 7.0,
color: Colors.white,
child: Column(
children: [
Row(
children: [
IconButton(
icon: Icon(
Icons.play_circle_outline,
color: Colors.black,
size: 30,
),
onPressed: () {},
),
Expanded(
child: ListTile(
title: Text(post.body,
style: TextStyle(
fontWeight: FontWeight.w600,
color: Colors.black)),
subtitle: Text(post.author,
style: TextStyle(color: Colors.black)),
),
),
Expanded(
child: Row(
mainAxisAlignment: MainAxisAlignment.end,
children: [
Text(post.usersLiked.length.toString(),
style: TextStyle(
color: Colors.black,
fontWeight: FontWeight.w600)),
IconButton(
icon: Icon(
Icons.thumb_up,
color: post.usersLiked.contains(widget.user.uid)
? Colors.blue
: Colors.black,
),
onPressed: () =>
this.like(() => post.likePost(widget.user)),
)
],
))
],
)
],
));
},
);
}
}


数据库.dart

final databaseReference = FirebaseDatabase.instance.reference();
DatabaseReference savePost(Post post) {
var id = databaseReference.child('posts/').push();
id.set(post.toJson());
return id;
}
void updatePost(Post post, DatabaseReference id) {
id.update(post.toJson());
}
Future> getAllPosts() async {
DataSnapshot dataSnapshot = await databaseReference.child('posts/').once();
List posts = [];
if (dataSnapshot.value != null) {
dataSnapshot.value.forEach((key, value) {
Post post = createPost(value);
post.setId(databaseReference.child('posts/' + key));
posts.add(post);
});
}
return posts;
}


家.dart

class UserInfoScreen extends StatefulWidget {
const UserInfoScreen({Key key, User user})
: _user = user,
super(key: key);
final User _user;
@override
_UserInfoScreenState createState() => _UserInfoScreenState();
}
class _UserInfoScreenState extends State {
User _user;
bool _isSigningOut = false;
List posts = [];
void newPost(String text) {
var post = new Post(text, widget._user.displayName);
post.setId(savePost(post));
this.setState(() {
posts.add(post);
});
}
void updatePosts() {
getAllPosts().then((posts) => {
this.setState(() {
this.posts = posts;
})
});
}
Route _routeToSignInScreen() {
return PageRouteBuilder(
pageBuilder: (context, animation, secondaryAnimation) => SignInScreen(),
transitionsBuilder: (context, animation, secondaryAnimation, child) {
var begin = Offset(-1.0, 0.0);
var end = Offset.zero;
var curve = Curves.ease;
var tween =
Tween(begin: begin, end: end).chain(CurveTween(curve: curve));
return SlideTransition(
position: animation.drive(tween),
child: child,
);
},
);
}
@override
void initState() {
_user = widget._user;
// HOME PAGE
pageList.add(Scaffold(
backgroundColor: Colors.white,
body: Column(children: [
Expanded(
child: PostList(this.posts, _user),
),
]),
));
pageList.add(Test1());
pageList.add(Scaffold(
backgroundColor: Colors.white,
body: Column(
children: [
TextInputWidget(this.newPost, "Title:"),
],
),
));
pageList.add(Test3());
// ACCOUNT PAGE
pageList.add(
Scaffold(
backgroundColor: Colors.white,
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Row(),
_user.photoURL != null
? ClipOval(
child: Material(
color: Colors.grey.withOpacity(0.3),
child: Image.network(
_user.photoURL,
fit: BoxFit.fitHeight,
),
),
)
: ClipOval(
child: Material(
color: Colors.grey.withOpacity(0.3),
child: Padding(
padding: const EdgeInsets.all(16.0),
child: Icon(
Icons.person,
size: 60,
color: Colors.black,
),
),
),
),
SizedBox(height: 16.0),
Text(
'${_user.displayName}',
style: TextStyle(
color: Colors.black,
fontSize: 26,
fontWeight: FontWeight.w700),
),
SizedBox(height: 8.0),
Text(
' ${_user.email} ',
style: TextStyle(
color: Colors.black,
fontSize: 20,
letterSpacing: 0.5,
),
),
SizedBox(height: 60.0),
_isSigningOut
? CircularProgressIndicator(
valueColor: AlwaysStoppedAnimation(Colors.white),
)
: ElevatedButton(
style: ButtonStyle(
backgroundColor: MaterialStateProperty.all(
Colors.redAccent,
),
shape: MaterialStateProperty.all(
RoundedRectangleBorder(
borderRadius: BorderRadius.circular(10),
),
),
),
onPressed: () async {
setState(() {
_isSigningOut = true;
});
await Authentication.signOut(context: context);
setState(() {
_isSigningOut = false;
});
Navigator.of(context)
.pushReplacement(_routeToSignInScreen());
},
child: Padding(
padding: EdgeInsets.only(top: 8.0, bottom: 8.0),
child: Text(
'Logout',
style: TextStyle(
fontSize: 20,
fontWeight: FontWeight.w500,
color: Colors.white,
),
),
),
),
],
),
),
);
super.initState();
updatePosts();
}
@override
List pageList = List();
int _currentIndex = 0;
void onTabTapped(int index) {
setState(() {
_currentIndex = index;
});
}
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
elevation: 0.0,
backgroundColor: Colors.white,
title: Text(
'SoundFX',
style: TextStyle(color: Colors.black),
),
centerTitle: true,
),
body: IndexedStack(
index: _currentIndex,
children: pageList,
),
bottomNavigationBar: BottomNavigationBar(
unselectedItemColor: Colors.grey,
selectedItemColor: Colors.blue,
backgroundColor: Colors.white,
elevation: 19.0,
onTap: onTabTapped,
currentIndex: _currentIndex,
type: BottomNavigationBarType.fixed,
items: [
BottomNavigationBarItem(
icon: new Icon(Icons.home),
title: Container(
height: 1.0,
)),
BottomNavigationBarItem(
icon: new Icon(Icons.search),
title: Container(
height: 1.0,
)),
BottomNavigationBarItem(
icon: new Icon(
Icons.add_circle,
size: 40,
),
title: Container(
height: 1.0,
)),
BottomNavigationBarItem(
icon: new Icon(Icons.videocam),
title: Container(
height: 1.0,
)),
BottomNavigationBarItem(
icon: Icon(Icons.account_circle),
title: Container(
height: 1.0,
)),
],
),
);
}
}
class Test1 extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
color: Colors.green,
);
}
}
class Test2 extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
color: Colors.blue,
);
}
}
class Test3 extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Container(
color: Colors.yellow,
);
}
}


文本输入.dart

class TextInputWidget extends StatefulWidget {
final Function(String) callback;
String label;
TextInputWidget(this.callback, this.label);
@override
_TextInputWidgetState createState() => _TextInputWidgetState();
}
class _TextInputWidgetState extends State {
final cOntroller= TextEditingController();
@override
void dispose() {
super.dispose();
controller.dispose();
}
void click() {
widget.callback(controller.text);
FocusScope.of(context).unfocus();
controller.clear();
}
void pickFiles() async {
FilePickerResult result =
await FilePicker.platform.pickFiles(type: FileType.any);
File file = File(result.files.first.path);
print(file);
}
@override
Widget build(BuildContext context) {
return Container(
height: 400,
child: Column(
mainAxisSize: MainAxisSize.min,
children: [
Expanded(
child: Container(
padding: EdgeInsets.all(20.0),
child: TextField(
controller: this.controller,
decoration: InputDecoration(
labelText: this.widget.label,
))),
),
Container(
child: ElevatedButton(onPressed: this.click, child: Text('Post')),
),
Container(
child:
ElevatedButton(onPressed: this.pickFiles, child: Text('test')),
)
],
),
);
}
}


PS：另外请注意，有些函数和类没有使用或基本没用，有些名称很愚蠢，但如果它们与问题无关，请不要评论，因为这些只是为了一些测试为我添加到应用程序的功能。

另请注意，我遵循了本教程 - https://www.youtube.com/playlist?list=PLzMcBGfZo4-knQWGK2IC49Q_5AnQrFpzv