在我的应用上从 firebase 退出后，我收到以下消息。
*Null check operator used on a null value
When the exception was thrown, this was the stack:
#0 MainScreenPage.build.<anonymous closure>.<anonymous closure>
(package:flutter_book_tracker_app/screens/main_screen_page.dart:274:49)
Null check operator used on a null value
When the exception was thrown, this was the stack:
#0 MainScreenPage.build.<anonymous closure>.<anonymous closure> (package:flutter_book_tracker_app/screens/main_screen_page.dart:66:45)
A RenderFlex overflowed by 199462 pixels on the bottom.
The relevant error-causing widget was:
Column file:///Users/junko/AndroidStudioProjects/flutter_book_tracker_app/flutter_book_tracker_app/lib/screens/main_screen_page.dart:132:13
A RenderFlex overflowed by 99671 pixels on the right.
The relevant error-causing widget was:
AppBar file:///Users/junko/AndroidStudioProjects/flutter_book_tracker_app/flutter_book_tracker_app/lib/screens/main_screen_page.dart:36:15*
- 显示的所有错误都在 main_screen_page.dart 上，但退出后模拟器窗口显示 login_screen_page。
- 单击模拟器上的 [返回] 按钮时，模拟器显示 main_screen_page.dart 并显示“在空值上使用空检查运算符”和“A RenderFlex 在底部溢出 199462 像素”错误。
<main_screen_page.dart>
class MainScreenPage extends StatelessWidget {
@override
Widget build(BuildContext context) {
CollectionReference userCollectionReference =
FirebaseFirestore.instance.collection('users');
CollectionReference bookCollectionReference =
FirebaseFirestore.instance.collection('books');
List<Book> userBooksReadList = [];
// int booksRead = 0;
var authUser = Provider.of<User?>(context);
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.white24,
elevation: 0,
toolbarHeight: 77,
centerTitle: false,
title: Row(
children: [
Image.asset(
'assets/images/Icon-76.png',
scale: 2,
),
Text(
'A.Reader',
style: Theme.of(context).textTheme.headline6!.copyWith(
color: Colors.redAccent, fontWeight: FontWeight.bold),
),
],
),
actions: [
StreamBuilder<QuerySnapshot>(
stream: userCollectionReference.snapshots(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return Center(
child: CircularProgressIndicator(),
);
}
final userListStream = snapshot.data!.docs.map((user) {
return MUser.fromDocument(user);
}).where((user) {
return (user.uid == authUser!.uid);
}).toList();
MUser curUser = userListStream[0];
return Column(
children: [
SizedBox(
height: 40,
width: 40,
child: InkWell(
onTap: () {
showDialog(
context: context,
builder: (context) {
return createProfileDialog(
context, curUser, userBooksReadList);
},
);
},
child: CircleAvatar(
radius: 60,
backgroundImage: NetworkImage(curUser.avatarUrl ??
'https://picsum.photos/id/1022/300'),
backgroundColor: Colors.white,
child: Text(''),
),
),
),
Text(
curUser.displayName.toUpperCase(),
overflow: TextOverflow.ellipsis,
style: TextStyle(color: Colors.black),
)
],
);
},
),
TextButton.icon(
onPressed: () {
FirebaseAuth.instance.signOut().then((value) {
return Navigator.push(
context,
MaterialPageRoute(
builder: (context) => LoginPage(),
));
});
},
icon: Icon(Icons.logout),
label: Text(''),
),
],
),
floatingActionButton: FloatingActionButton(
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => BookSearchPage(),
));
},
child: Icon(
Icons.add,
),
backgroundColor: Colors.redAccent,
),
body: Column(
children: [
Container(
width: double.infinity,
margin: const EdgeInsets.only(top: 12, left: 12, bottom: 10),
child: RichText(
text: TextSpan(
style: Theme.of(context).textTheme.headline6,
children: [
TextSpan(text: '今、'),
TextSpan(
text: '読んでいるのは',
style: TextStyle(fontWeight: FontWeight.w600)),
TextSpan(text: '…'),
]),
),
),
SizedBox(
height: 10,
),
StreamBuilder<QuerySnapshot>(
stream: bookCollectionReference.snapshots(),
builder: (context, snapshot) {
if (snapshot.hasError) {
return Text('問題が発生しました (T.T)');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return Expanded(
flex: 1,
child: Center(
child: CircularProgressIndicator(
strokeWidth: 2,
color: Colors.lime.shade300,
)));
}
if (snapshot.data!.docs.isEmpty) {
return Text('表示する書籍データがありません',
style: Theme.of(context).textTheme.headline4);
}
final userBookFilteredReadListStream =
snapshot.data!.docs.map((book) {
return Book.fromDocument(book);
}).where((book) {
return ((book.userId == authUser!.uid)) &&
(book.finishedReading == null) &&
(book.startedReading != null);
}).toList();
userBooksReadList = snapshot.data!.docs.map((book) {
return Book.fromDocument(book);
}).where((book) {
return ((book.userId == authUser!.uid)) &&
(book.finishedReading != null) &&
(book.startedReading != null);
}).toList();
return Expanded(
flex: 1,
child: (userBookFilteredReadListStream.length > 0)
? ListView.builder(
scrollDirection: Axis.horizontal,
itemCount: userBookFilteredReadListStream.length,
itemBuilder: (context, index) {
Book book = userBookFilteredReadListStream[index];
return InkWell(
child: ReadingListCard(
buttonText: '読書中',
image: book.photoUrl!,
title: book.title,
author: book.author!,
rating: book.rating!,
),
onTap: () {
showDialog(
context: context,
builder: (context) {
return BookDetailDialog(
book: book,
);
},
);
},
);
},
)
: Text('読書中の本はありません (・o・)',
style: Theme.of(context).textTheme.headline6));
},
),
Container(
width: double.infinity,
margin: EdgeInsets.only(left: 10),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
RichText(
text: TextSpan(children: [
TextSpan(
text: '読みたい本リスト',
style: TextStyle(
fontSize: 24,
fontWeight: FontWeight.w600,
color: kBlackColor),
),
]),
),
],
),
),
SizedBox(
height: 8,
),
StreamBuilder<QuerySnapshot>(
stream: bookCollectionReference.snapshots(),
builder: (context, snapshot) {
if (snapshot.hasError) {
return Text('問題が発生しました (T.T)');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return Expanded(
flex: 1,
child: Center(
child: CircularProgressIndicator(
strokeWidth: 2,
color: Colors.lime.shade300,
)));
}
if (snapshot.data!.docs.isEmpty) {
return Center(
child: Text('表示する書籍データがありません',
style: Theme.of(context).textTheme.headline4),
);
}
final readingListListBook = snapshot.data!.docs.map((book) {
return Book.fromDocument(book);
// ログイン中ユーザのuidでbookをフィルタリングする
}).where((book) {
return ((book.userId == authUser!.uid)) &&
(book.startedReading == null) &&
(book.finishedReading == null);
}).toList();
return Expanded(
flex: 1,
child: (readingListListBook.length > 0)
? ListView.builder(
scrollDirection: Axis.horizontal,
itemCount: readingListListBook.length,
itemBuilder: (context, index) {
Book book = readingListListBook[index];
return InkWell(
child: ReadingListCard(
buttonText: '未読',
rating: book.rating!,
image: book.photoUrl!,
title: book.title,
author: book.author!,
isBookRead: false,
),
onTap: () {
showDialog(
context: context,
builder: (context) {
return BookDetailDialog(
book: book,
);
},
);
},
);
},
)
: Text('表示する書籍データがありません ^_^;',
style: Theme.of(context).textTheme.headline6));
},
),
],
),
);
}
}
“授权用户！” 退出后似乎导致了空检查问题，因为退出时 authUser 变为空。
我尝试通过在每次出现 authUser! 之前添加“if (authUser == null) {}”来解决空值检查问题，结果出现错误“setState() 或 markNeedsBuild() 在构建期间调用”和“'package:flutter /src/widgets/navigator.dart'：断言失败：第 4564 行 pos 12：'！_debugLocked'：不正确。” （在相同的两个 RenderFlex 问题之上。）
谁能帮我解决这些问题？