Flutter ListView CastError 仅在热重载时
[英]Flutter ListView CastError only on Hot Reload
问题描述
I notify a very strange bug in my Flutter app.
我在我的 Flutter 应用程序中发现了一个非常奇怪的错误。 I'm using a ListView with an itemExtend value.我正在使用带有itemExtend值的ListView 。 When navigating inside the app everything is working fine – no error messages in the console.在应用程序内部导航时，一切正常——控制台中没有错误消息。 But after a Hot Reload, for example by editing and saving the code on the file on which the ListView is placed, I get many RenderRepaintBoundary errors.但是在热重载之后，例如通过编辑和保存放置 ListView 的文件上的代码，我会收到很多RenderRepaintBoundary错误。
This is my ListView:这是我的列表视图：
return ListView.builder(
padding: EdgeInsets.only(top: 25, bottom: 20),
shrinkWrap: true,
itemExtent: 95, // Error only appears if I add itemExtent
physics: ClampingScrollPhysics(),
itemCount: entriesController.guestbookEntries.length,
itemBuilder: (BuildContext context, int index) {
return GestureDetector(
onLongPress: () async {
// Some stuff
},
child: Text("Test Widget")
);
},
);
After Hot Reload I get the following error messages in the console (But the app works as expected):热重载后，我在控制台中收到以下错误消息（但该应用程序按预期工作）：
[Easy Localization] Build [Easy Localization] Init Localization Delegate [Easy Localization] Init provider
════════ Exception caught by rendering library ═════════════════════════════════ The following _CastError was thrown during performLayout(): Null check operator used on a null value
The relevant error-causing widget was ListView When the exception was thrown, this was the stack #0 RenderSliverFixedExtentBoxAdaptor.performLayout #1 RenderObject.layout #2 RenderSliverEdgeInsetsPadding.performLayout #3 RenderSliverPadding.performLayout #4 RenderObject.layout... The following RenderObject was being processed when the exception was fired: RenderSliverFixedExtentList#b073b relayoutBoundary=up11 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE RenderObject: RenderSliverFixedExtentList#b073b relayoutBoundary=up11 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE needs compositing parentData: paintOffset=Offset(0.0, 25.0) (can use size) constraints: SliverConstraints(AxisDirection.down, GrowthDirection.forward, ScrollDirection.idle, scrollOffset: 0.0, remainingPaintExtent: Infinity, crossAxisExtent: 390.0, crossAxisDirection: AxisDirection.right, viewportMainAxisExtent: Infinity, remainingCacheExtent: Infinity, cacheOrigin: 0.0) geometry: SliverGeometry(scrollEx
Do you have an idea what happens here and why without Hot Reload everything works fine?你知道这里发生了什么吗？为什么没有热重载一切正常？ And how to fix such an error?以及如何解决这样的错误？ I tried to remove the itemExtend .我试图删除itemExtend 。 Then it works and the error does not appear.然后它工作并且没有出现错误。 But without itemExtend I have some flickering in my ListView.但是如果没有 itemExtend，我的 ListView 会出现一些闪烁。 Looks like order changing or something else.看起来像订单更改或其他东西。 Its very ugly.它非常丑陋。 Therefore I need to itemExtend to fix it.因此我需要 itemExtend 来修复它。
If you need a better view of the code context, I send you the code of the entire file.如果您需要更好地了解代码上下文，我会将整个文件的代码发送给您。 By the way.顺便一提。 There are still no gos like handling data inside a build method.仍然没有像在构建方法中处理数据那样的方法。 Its an old project and I'm on the way to rewrite it entirely.它是一个旧项目，我正在完全重写它。 But this things are not responsible for the error.但是这个东西出错概不负责。 It is interesting, that the error does not appear when I remove "itemExtend".有趣的是，当我删除“itemExtend”时，错误并没有出现。 How is that possible?这怎么可能？
The entire code:整个代码：
class GuestGuestbookContent extends StatelessWidget {
GuestGuestbookContent({
Key key,
}) : super(key: key);
GuestbooksController get guestbooksController => Get.find();
EntriesController get entriesController => Get.find();
UsersController get usersController => Get.find();
@override
Widget build(BuildContext context) {
return SliverToBoxAdapter(
child: Container(
padding: EdgeInsets.only(bottom: 50, top: 50),
alignment: Alignment.center,
child: entriesController.obx((state) {
return Column(
children: [
Container(
child: MixinBuilder(
initState: (_) async {
await entriesController.checkGuestbookForUserEntries(
guestbooksController.currentGuestbook.value.id);
},
builder: (_) {
if (entriesController.hasUserEntry.value == true) {
return Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Container(
padding:
const EdgeInsets.only(left: 25.0, right: 25),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Text("your_entries",
style: Get.theme.textTheme.headline4)
.tr(),
IconButton(
alignment: Alignment.centerRight,
padding: EdgeInsets.all(0),
icon: Icon(
entriesController.showOwnEntries.value ==
false
? CupertinoIcons.arrow_down
: CupertinoIcons.arrow_up,
color: Get.theme.colorScheme.primary,
size: 20,
),
onPressed: () => entriesController
.showOwnEntries.value =
!entriesController.showOwnEntries.value)
],
),
),
entriesController.showOwnEntries.value == true
? _buildUserEntries()
: Container(),
SizedBox(height: 15),
],
);
} else {
bool isOpen = true;
DateTime startDate;
if (guestbooksController
.currentGuestbook.value.startDate !=
null) {
startDate = DateTime.parse(guestbooksController
.currentGuestbook.value.startDate);
isOpen = startDate.isAtSameMomentAs(DateTime.now()) ||
startDate.isBefore(DateTime.now());
}
if (isOpen) {
return _buildAddEntryButton();
} else {
return Container(
child: Column(
children: [
Image.asset("assets/animations/clock.gif",
width:
context.isTablet ? 400 : Get.width / 2),
SizedBox(
height: 15,
),
Text("guestbook_opens_at").tr(),
SizedBox(height: 5),
Text(
DateFormat(tr("date_format"))
.format(startDate),
style: Get.theme.textTheme.headline1)
],
),
);
}
}
},
),
),
// Alle Einträge
guestbooksController.currentGuestbook.value.isPublic == true ||
_isModerator() == true
? _buildAllEntriesContainer()
: Container(),
],
);
}, onLoading: LoadingSpinner()),
),
);
}
bool _isModerator() {
return usersController.userIsModerator(
userID: usersController.ownUser.value.uid,
guestbook: guestbooksController.currentGuestbook.value);
}
CupertinoButton _buildAddEntryButton() {
return CupertinoButton(
child: Column(
children: [
Icon(
Icons.add,
size: 50,
),
Text(
"create_entry",
style:
TextStyle(color: Get.theme.colorScheme.primary, fontSize: 20),
).tr(),
SizedBox(height: 25),
],
),
onPressed: () => Get.toNamed("writeNewEntry"));
}
ListView _buildUserEntries() {
return ListView.builder(
shrinkWrap: true,
padding: EdgeInsets.only(top: 0, bottom: 10),
physics: ClampingScrollPhysics(),
itemCount: entriesController.userEntriesData.length,
itemBuilder: (BuildContext context, int index) {
final Entry entry = entriesController.userEntriesData[index];
// Manage description
String entryContent = "";
List entryContentInput = [];
if (entry.content != null) {
final parsedContent = jsonDecode(entry.content);
if (parsedContent != null) {
for (int i = 0; i < parsedContent.length; i++) {
entryContentInput.add(parsedContent[i]["insert"]);
}
entryContent = entryContentInput.join("").toString();
}
}
return GestureDetector(
onLongPress: () {
_userEntryOptions(entry);
},
child: GuestListTile(
entry: entry,
description: entryContent != null && entryContent.isNotEmpty
? entryContent
: tr("no_text_added"),
owner: entry.owner,
hasImages: entry.images != null && entry.images.isNotEmpty,
hasVideos: entry.videos != null && entry.videos.isNotEmpty,
hasPainting:
entry.paintingImage != null && entry.paintingImage.isNotEmpty,
),
);
});
}
Container _buildAllEntriesContainer() {
return Container(
child: MixinBuilder(
builder: (EntriesController controller) {
if (controller.guestbookEntriesWithoutOwn.length > 0) {
return Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Padding(
padding: const EdgeInsets.only(left: 25.0, right: 25),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Text("entries_from_all_guests",
style: Get.theme.textTheme.headline4)
.tr(),
CircleAvatar(
radius: 10,
backgroundColor: Get.theme.colorScheme.primary,
child: Text(
controller.guestbookEntriesWithoutOwn.length
.toString(),
style: TextStyle(
fontSize: 10,
color: Get.theme.colorScheme.background)),
)
],
),
),
_buildAllEntries(controller.guestbookEntriesWithoutOwn),
],
);
} else {
return Container();
}
},
),
);
}
Widget _buildAllEntries(List<Entry> entries) {
if (entries != null && entries.isNotEmpty) {
return ListView.builder(
padding: EdgeInsets.only(top: 10, bottom: 10),
physics: ClampingScrollPhysics(),
shrinkWrap: true,
itemExtent: 95,
itemCount: entries.length,
itemBuilder: (BuildContext context, int index) {
Entry entry;
if (entries.length > 0) {
entry = entries[index];
// Manage description
String entryContent = "";
List entryContentInput = [];
if (entry.content != null) {
final parsedContent = jsonDecode(entry.content);
if (parsedContent != null) {
for (int i = 0; i < parsedContent.length; i++) {
entryContentInput.add(parsedContent[i]["insert"]);
}
entryContent = entryContentInput.join("").toString();
}
}
return GestureDetector(
onLongPress: () async {
final userID = await getUid();
if (usersController.userIsModerator(
userID: userID,
guestbook:
guestbooksController.currentGuestbook.value) ==
true) {
_userEntryOptions(entry);
}
},
child: GuestListTile(
entry: entry,
description: entryContent != null &&
entryContent.isNotEmpty &&
entryContent != "\n"
? entryContent
: tr("no_content"),
owner: entry.owner,
hasImages: entry.images != null && entry.images.isNotEmpty,
hasVideos: entry.videos != null && entry.videos.isNotEmpty,
hasPainting: entry.paintingImage != null &&
entry.paintingImage.isNotEmpty,
),
);
} else {
return Container();
}
});
} else {
return Container();
}
}
void _userEntryOptions(Entry entry) {
Get.bottomSheet(CupertinoActionSheet(
actions: [
CupertinoActionSheetAction(
onPressed: () {
Get.back();
_deleteUserEntryConfirmation(entry);
},
child: Text("delete_this_entry").tr(),
isDestructiveAction: true,
)
],
));
}
void _deleteUserEntryConfirmation(Entry entry) {
Get.dialog(CupertinoAlertDialog(
title: Text("delete_my_entry_desc").tr(),
actions: [
CupertinoDialogAction(
child: Text("yes_delete_entry").tr(),
isDestructiveAction: true,
onPressed: () {
Get.back();
_deleteUserEntry(entry);
},
),
CupertinoDialogAction(
child: Text("no_not_delete_entry").tr(),
onPressed: () {
Get.back();
},
)
],
));
}
void _deleteUserEntry(Entry entry) async {
await entriesController.deleteEntireUserEntry(entry);
await MySnackbar()
.createSnackbar(message: tr("entry_deleted_successfully"), seconds: 2);
}
}
By the way: I'm using the getx package for state management.顺便说一句：我正在使用 getx package 进行 state 管理。 This is the reason because I can go with a Stateless widget.这是因为我可以使用Stateless小部件 go。
4 个解决方案
解决方案1
0 2022-06-03 08:32:14
Rebuild the app using the command flutter clean使用命令flutter clean重建应用程序
解决方案2
0 2022-06-07 06:21:47
You didn't provide a lot of code, but maybe you should try wrapping your ListView.builder with Expanded widget?你没有提供很多代码，但也许你应该尝试用Expanded小部件包装你的ListView.builder ？ :) :)
Then your code would become something like:然后你的代码会变成这样：
return Expanded(
child: ListView.builder(
padding: EdgeInsets.only(top: 25, bottom: 20),
shrinkWrap: true,
itemExtent: 95,
physics: ClampingScrollPhysics(),
itemCount: entriesController.guestbookEntries.length,
itemBuilder: (BuildContext context, int index) {
return GestureDetector(
onLongPress: () async {
// Some stuff
},
child: GuestListTile()
);
},
));
The Expanded widget consumes available space which comes in handy if used in a Column or a Row -- you can read more about it @ Flutter - Expanded . Expanded小部件会占用可用空间，如果在Column或Row中使用它会派上用场 - 您可以阅读有关它的更多信息 @ Flutter - Expanded 。
解决方案3
0 2022-06-08 03:38:11
It seems your guestbookEntries from entriesController variable is null when you do hot reload.当您进行热重载时，您的entriesController变量中的guestbookEntries似乎是 null。 Check the value if null show some loading indicator, then show the ListView when it's not null.如果 null 显示一些加载指示器，请检查该值，然后在它不是 null 时显示ListView 。
Your widget doesn't show anything much, because there is no controller class code.您的小部件没有显示任何内容，因为没有 controller class 代码。
解决方案4
0 2022-06-08 05:45:10
Use this: Your Problem will be solved使用这个：你的问题将得到解决
return Container(
height: double.maxfinite;
child:SingleChildScrollView(
child: ListView.builder(
padding: EdgeInsets.only(top: 25, bottom: 20),
shrinkWrap: true,
itemExtent: 95,
physics: NeverScrollableScrollPhysics(),
itemCount: entriesController.guestbookEntries.length,
itemBuilder: (BuildContext context, int index) {
return GestureDetector(
onLongPress: () async {
// Some stuff
},
child: GuestListTile()
);
},
)));
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