错误：“ _ elements.contains（element）”：不正确 [英] Error: '_elements.contains(element)': is not true

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本文介绍了错误：“ _ elements.contains（element）”：不正确的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我看到了这个错误'_ elements.contains（element）'：不正确。在我的flutter项目中，过去两天里，这工作得很好，因为开始。我很遗憾地说这句话，但是我对这个错误一无所知，但是我想我正在丢失导致此错误的东西。另外，当我热重新加载同一页面时，会填充布局，但会引发异常。

I am seeing this error '_elements.contains(element)': is not true.for the past two days in my flutter project, this was working absolutely fine since the beginning. I am sorry to say this but I have no clue regarding this error but i think i am missing something which is causing this error. Also, when I hot reload the same page the layout is populated, but throws the exceptions.

间歇地此操作还会显示检测到Duplicate GlobalKeys（），但这不是

Intermittently this was also showing Duplicate GlobalKeys() detected, but this wasn't the case in the beginning.

如果以前偶然发现这些错误，请帮助我。我真的不能写一个例子来重现同样的问题。非常感谢。

Please can someone help me if they stumbled upon these errors before. I couldn't really write an example to reproduce the same problem. Many thanks.

我给出了以下错误详细信息：

I have given the error details as follows:

Performing hot reload...
I/flutter (22248): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY 
╞═══════════════════════════════════════════════════════════
I/flutter (22248): The following assertion was thrown building 
TickerMode(mode: disabled):
I/flutter (22248): 'package:flutter/src/widgets/framework.dart': Failed 
assertion: line 1766 pos 12:
I/flutter (22248): '_elements.contains(element)': is not true.
I/flutter (22248): 
I/flutter (22248): Either the assertion indicates an error in the framework 
itself, or we should provide substantially
I/flutter (22248): more information in this error message to help you 
determine and fix the underlying cause.
I/flutter (22248): In either case, please report this assertion by filing a 
bug on GitHub:
I/flutter (22248):   https://github.com/flutter/flutter/issues/new
I/flutter (22248): 
I/flutter (22248): When the exception was thrown, this was the stack:
I/flutter (22248): #2      _InactiveElements.remove 
 (package:flutter/src/widgets/framework.dart:1766:12)
I/flutter (22248): #3      Element._retakeInactiveElement 
(package:flutter/src/widgets/framework.dart:2850:29)
I/flutter (22248): #4      Element.inflateWidget 
(package:flutter/src/widgets/framework.dart:2873:32)
I/flutter (22248): #5      Element.updateChild 
(package:flutter/src/widgets/framework.dart:2688:12)
I/flutter (22248): #6      ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #7      Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #8      ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3792:5)
I/flutter (22248): #9      Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #10     RenderObjectElement.updateChildren 
(package:flutter/src/widgets/framework.dart:4262:32)
I/flutter (22248): #11     _TheatreElement.update 
(package:flutter/src/widgets/overlay.dart:508:17)
I/flutter (22248): #12     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #13     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #14     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #15     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3682:5)
I/flutter (22248): #16     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #17     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #18     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #19     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3792:5)
I/flutter (22248): #20     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #21     SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4535:14)
I/flutter (22248): #22     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #23     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #24     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #25     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3682:5)
I/flutter (22248): #26     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #27     SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4535:14)
I/flutter (22248): #28     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #29     SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4535:14)
I/flutter (22248): #30     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #31     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #32     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #33     StatefulElement.update 
(package:flutter/src/widgets/framework.dart:3682:5)
I/flutter (22248): #34     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #35     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #36     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #37     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3792:5)
I/flutter (22248): #38     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #39     SingleChildRenderObjectElement.update 
(package:flutter/src/widgets/framework.dart:4535:14)
I/flutter (22248): #40     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #41     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #42     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #43     StatelessElement.update 
(package:flutter/src/widgets/framework.dart:3607:5)
I/flutter (22248): #44     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #45     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
I/flutter (22248): #46     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #47     StatelessElement.update 
(package:flutter/src/widgets/framework.dart:3607:5)
I/flutter (22248): #48     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #49     ComponentElement.performRebuild  
(package:flutter/src/widgets/framework.dart:3557:16)
 I/flutter (22248): #50     Element.rebuild 
 (package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #51     StatelessElement.update 
(package:flutter/src/widgets/framework.dart:3607:5)
I/flutter (22248): #52     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
 I/flutter (22248): #53     ComponentElement.performRebuild 
(package:flutter/src/widgets/framework.dart:3557:16)
 I/flutter (22248): #54     Element.rebuild 
(package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #55     StatelessElement.update 
(package:flutter/src/widgets/framework.dart:3607:5)
I/flutter (22248): #56     Element.updateChild 
(package:flutter/src/widgets/framework.dart:2677:15)
I/flutter (22248): #57     ComponentElement.performRebuild                                              
 (package:flutter/src/widgets/framework.dart:3557:16)
 I/flutter (22248): #58     Element.rebuild 
 (package:flutter/src/widgets/framework.dart:3446:5)
I/flutter (22248): #59     ProxyElement.update 
(package:flutter/src/widgets/framework.dart:3792:5)
 I/flutter (22248): #60     Element.updateChild 
 (package:flutter/src/widgets/framework.dart:2677:15)
  I/flutter (22248): #61     ComponentElement.performRebuild 
 (package:flutter/src/widgets/framework.dart:3557:16)
 I/flutter (22248): #62     Element.rebuild 
 (package:flutter/src/widgets/framework.dart:3446:5)
 I/flutter (22248): #63     ProxyElement.update 
 (package:flutter/src/widgets/framework.dart:3792:5)
  I/flutter (22248): #64     Element.updateChild 
  (package:flutter/src/widgets/framework.dart:2677:15)
  I/flutter (22248): #65     ComponentElement.performRebuild 
  (package:flutter/src/widgets/framework.dart:3557:16)
          I/flutter (22248): #66     Element.rebuild 
   (package:flutter/src/widgets/framework.dart:3446:5)
  I/flutter (22248): #67     StatefulElement.update 
  (package:flutter/src/widgets/framework.dart:3682:5)
  I/flutter (22248): #68     Element.updateChild 
    (package:flutter/src/widgets/framework.dart:2677:15)
  I/flutter (22248): #69     ComponentElement.performRebuild 
  (package:flutter/src/widgets/framework.dart:3557:16)
    I/flutter (22248): #70     Element.rebuild 
   (package:flutter/src/widgets/framework.dart:3446:5)
    I/flutter (22248): #71     ProxyElement.update 
  (package:flutter/src/widgets/framework.dart:3792:5)
  I/flutter (22248): #72     Element.updateChild 
  (package:flutter/src/widgets/framework.dart:2677:15)
   I/flutter (22248): #73     ComponentElement.performRebuild 
  (package:flutter/src/widgets/framework.dart:3557:16)
  I/flutter (22248): #74     Element.rebuild 
  (package:flutter/src/widgets/framework.dart:3446:5)
  I/flutter (22248): #75     StatefulElement.update 
 (package:flutter/src/widgets/framework.dart:3682:5)
  I/flutter (22248): #76     Element.updateChild 
 (package:flutter/src/widgets/framework.dart:2677:15)
 I/flutter (22248): #77     ComponentElement.performRebuild 
  (package:flutter/src/widgets/framework.dart:3557:16)
  I/flutter (22248): #78     Element.rebuild 
  (package:flutter/src/widgets/framework.dart:3446:5)
   I/flutter (22248): #79     ProxyElement.update 
  (package:flutter/src/widgets/framework.dart:3792:5)
   I/flutter (22248): #80     Element.updateChild 
    (package:flutter/src/widgets/framework.dart:2677:15)
 I/flutter (22248): #81     ComponentElement.performRebuild 
     (package:flutter/src/widgets/framework.dart:3557:16)
    I/flutter (22248): #82     Element.rebuild 
     (package:flutter/src/widgets/framework.dart:3446:5)
      I/flutter (22248): #83     ProxyElement.update 
     (package:flutter/src/widgets/framework.dart:3792:5)
   I/flutter (22248): #84     Element.updateChild 
    (package:flutter/src/widgets/framework.dart:2677:15)
   I/flutter (22248): #85     ComponentElement.performRebuild 
    (package:flutter/src/widgets/framework.dart:3557:16)
       I/flutter (22248): #86     Element.rebuild 
 (package:flutter/src/widgets/framework.dart:3446:5)
  I/flutter (22248): #87     StatelessElement.update 
     (package:flutter/src/widgets/framework.dart:3607:5)
   I/flutter (22248): #88     Element.updateChild 
  (package:flutter/src/widgets/framework.dart:2677:15)
     I/flutter (22248): #89     ComponentElement.performRebuild 
  (package:flutter/src/widgets/framework.dart:3557:16)
   I/flutter (22248): #90     Element.rebuild 
  (package:flutter/src/widgets/framework.dart:3446:5)
     I/flutter (22248): #91     StatefulElement.update 
  (package:flutter/src/widgets/framework.dart:3682:5)
  I/flutter (22248): #92     Element.updateChild 
  (package:flutter/src/widgets/framework.dart:2677:15)
  I/flutter (22248): #93     ComponentElement.performRebuild 
  (package:flutter/src/widgets/framework.dart:3557:16)
   I/flutter (22248): #94     Element.rebuild 
  (package:flutter/src/widgets/framework.dart:3446:5)
  I/flutter (22248): #95     ProxyElement.update 
    (package:flutter/src/widgets/framework.dart:3792:5)
   I/flutter (22248): #96     Element.updateChild 
   (package:flutter/src/widgets/framework.dart:2677:15)
   I/flutter (22248): #97     ComponentElement.performRebuild 
   (package:flutter/src/widgets/framework.dart:3557:16)
    I/flutter (22248): #98     Element.rebuild 
   (package:flutter/src/widgets/framework.dart:3446:5)
    I/flutter (22248): #99     BuildOwner.buildScope 
    (package:flutter/src/widgets/framework.dart:2246:33)
      I/flutter (22248): #100    












      BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&Renderer
     Binding&WidgetsBinding.drawFrame 
      (package:flutter/src/widgets/binding.dart:580:20)
       I/flutter (22248): #101    





    BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&Renderer
  Binding._handlePersistentFrameCallback 
   (package:flutter/src/rendering/binding.dart:200:5)
    I/flutter (22248): #102    
    BindingBase&SchedulerBinding._invokeFrameCallback 
   (package:flutter/src/scheduler/binding.dart:713:15)
   I/flutter (22248): #103    BindingBase&SchedulerBinding.handleDrawFrame 
     (package:flutter/src/scheduler/binding.dart:649:9)
     I/flutter (22248): #104    




   BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&Renderer
   Binding.scheduleWarmUpFrame.<anonymous closure> 
    (package:flutter/src/rendering/binding.dart:286:20)
   I/flutter (22248): #106    _Timer._runTimers (dart:isolate-
      patch/dart:isolate/timer_impl.dart:367)
      I/flutter (22248): #107    _Timer._handleMessage (dart:isolate-
     patch/dart:isolate/timer_impl.dart:401)
     I/flutter (22248): #108    _RawReceivePortImpl._handleMessage 
       (dart:isolate-patch/dart:isolate/isolate_patch.dart:163)
         I/flutter (22248): (elided 3 frames from class _AssertionError and 
       package dart:async-patch)
       I/flutter (22248): 

  ══════════════════════════════════════════════════════════════════════════
  ══════════════════════════
  Reloaded 0 of 492 libraries in 823ms.

我提供了一个示例示例，说明我正在尝试在应用程序中执行的操作。

I have included a sample example of what i am trying to do in my application.

main.dart

main.dart

import 'package:flutter/rendering.dart';
import 'package:flutter/material.dart';
import 'package:untitled3/secondwidget.dart';

void main() {
  runApp(
    new Example(),
  );
}

class Example extends StatefulWidget {
  @override
  _ExampleState createState() => new _ExampleState();
}

class _ExampleState extends State<Example> {
  int noOfBranches;

  @override
  void initState() {
    super.initState();
    getCount();
  }

  void getCount() {
    print('list builder count is ${noOfBranches}');
  }

  @override
  Widget build(BuildContext context) {
    setState(() {
      noOfBranches = 2;
    });

    return new MaterialApp(
      home: new Scaffold(
        body: new ListView.builder(
        itemCount: noOfBranches,
        itemBuilder: (BuildContext context, int index) {
          return new Card(
            child: new FlatButton(
                onPressed: (() {
                  Navigator.push(
                      context,
                      new MaterialPageRoute(
                          builder: (_) => new SecondWidget()));
                }),
                child: new Text('Next Widget')),
          );
        }),
      ),
    );
  }
 }

secondwidget.dart

secondwidget.dart

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

  class SecondWidget extends StatefulWidget {
  @override
 _SecondWidgetState createState() => new _SecondWidgetState();
 }

 class _SecondWidgetState extends State<SecondWidget> {
  @override
  Widget build(BuildContext context) {
    return new Container(
      child: new Text('Second Widget'),
   );
  }
 }

如果我看不到我的应用程序中的错误， setState（）声明为
中的示例main.dart文件中给出的 @override
Widget build（BuildContext context） {
setState（（）{
noOfBranches = 2;
}）;
.....
}

I don't see the error in my application if setState() declare as given in the example main.dart file inside the @override Widget build(BuildContext context) { setState(() { noOfBranches = 2; }); ..... }

但我只在声明<$ c $时看到此错误 getCount（）函数内的c> setState（）。

but I only see this error if I declare the setState() inside the getCount() function.

我不是

我实际上在这个错误上停留了两天，任何帮助将不胜感激。

I am actually stuck on this error for two days and any help would be greatly appreciated.

非常感谢，
Mahi

Many Thanks, Mahi

推荐答案

为什么不设置 noOfBranches 变量不在 initState 方法中吗？

Why don't you set your noOfBranches variable not in the initState method?

@override
void initState() {
  super.initState();
  noOfBranches = 2;
}

这篇关于错误：“ _ elements.contains（element）”：不正确的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！

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