2

使用 Provider 和 FutureBuilder，我刚刚从数据库中删除了数据，它同时被删除，它显示一个红色屏幕，状态不好，没有元素。添加数据没有问题，不显示这个问题。代码如下

堆栈跟踪

ter (12519): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (12519): The following StateError was thrown building ViewNoteScreen(dirty, dependencies:
I/flutter (12519): [_ModalScopeStatus], state: _ViewNoteScreenState#f589b):
I/flutter (12519): Bad state: No element
I/flutter (12519): 
I/flutter (12519): The relevant error-causing widget was:
I/flutter (12519):   ViewNoteScreen file:///C:/Users/Admin/Desktop/daily%2010/provider_note/lib/main.dart:21:46
I/flutter (12519):
I/flutter (12519): When the exception was thrown, this was the stack:
I/flutter (12519): #0      ListMixin.firstWhere (dart:collection/list.dart:148:5)
I/flutter (12519): #1      Providers.findById (package:provider_note/helper/provider.dart:14:19)
I/flutter (12519): #2      _ViewNoteScreenState.build (package:provider_note/screens/view_note.dart:21:35)
I/flutter (12519): #3      StatefulElement.build (package:flutter/src/widgets/framework.dart:4663:28)
I/flutter (12519): #4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4546:15)
I/flutter (12519): #5      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4719:11)
I/flutter (12519): #6      Element.rebuild (package:flutter/src/widgets/framework.dart:4262:5)
I/flutter (12519): #7      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2667:33)
I/flutter (12519): #8      WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:866:20)
I/flutter (12519): #9      RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:286:5)
I/flutter (12519): #10     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1117:15)
I/flutter (12519): #11     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1056:9)
I/flutter (12519): #12     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:972:5)
I/flutter (12519): #16     _invoke (dart:ui/hooks.dart:253:10)
I/flutter (12519): #17     _drawFrame (dart:ui/hooks.dart:211:3)
I/flutter (12519): (elided 3 frames from dart:async)
I/flutter (12519):
I/flutter (12519): ══════════════════════════════════════════════
4

2 回答 2

5

BadStateException当列表不包含该项目并且仍然有人搜索该项目时发生

例子：

如果orElse未在代码中定义并且错误的项目得到列表中不存在的搜索，则显示BadStateException

 void main() {
      List<String> list = ['red', 'yellow', 'pink', 'blue'];
      var newList = list.firstWhere((element) => element.contains('green'));
      print(newList);
    }

输出：

Uncaught Error: Bad state: No element

解决方案：添加 orElse

 void main() {
      List<String> list = ['red', 'yellow', 'pink', 'blue'];
      var newList = list.firstWhere((element) => element.contains(''), 
          orElse: () => 'No matching color found');
      print(newList);
    }

输出：

No matching color found
于 2020-10-02T13:19:35.803 回答
0

我认为对您来说最简单的方法是将您的主页更改为有状态的小部件并更改这部分代码。

Navigator.pushNamed(
 context, ViewNoteScreen.routeName,
     arguments: notes.items[i].id).whenComplete(() {
      setState(() {});
    });
于 2020-10-02T10:27:45.813 回答