getx控制器使用一次后返回null

如何解决getx控制器使用一次后返回null

我正在开发一个应用程序（类似于用于计算的测验应用程序）。对于每个屏幕，我都有一个控制器，其中一个屏幕是结果屏幕。在第一次尝试中一切正常，但是，在第二次尝试中，当我完成测验时，结果屏幕返回 null 并说“在 null 值上使用了 null 检查运算符。

这是抛出的异常


════════ Exception caught by widgets library ═══════════════════════════════════
The following _CastError was thrown building _BodyBuilder:
Null check operator used on a null value

The relevant error-causing widget was
Scaffold
lib/…/view/result_screen.dart:27
When the exception was thrown,this was the stack
#0      GetBuilderState.initState
package:get/…/simple/get_state.dart:134
#1      StatefulElement._firstBuild
package:flutter/…/widgets/framework.dart:4770
#2      ComponentElement.mount
package:flutter/…/widgets/framework.dart:4605
...     Normal element mounting (19 frames)
#21     Element.inflateWidget
package:flutter/…/widgets/framework.dart:3662
#22     MultiChildRenderObjectElement.inflateWidget
package:flutter/…/widgets/framework.dart:6285
#23     MultiChildRenderObjectElement.mount
package:flutter/…/widgets/framework.dart:6296
...     Normal element mounting (111 frames)
#134    Element.inflateWidget
package:flutter/…/widgets/framework.dart:3662
#135    MultiChildRenderObjectElement.inflateWidget
package:flutter/…/widgets/framework.dart:6285
#136    MultiChildRenderObjectElement.mount
package:flutter/…/widgets/framework.dart:6296
...     Normal element mounting (9 frames)
#145    Element.inflateWidget
package:flutter/…/widgets/framework.dart:3662
#146    MultiChildRenderObjectElement.inflateWidget
package:flutter/…/widgets/framework.dart:6285
#147    MultiChildRenderObjectElement.mount
package:flutter/…/widgets/framework.dart:6296
...     Normal element mounting (170 frames)
#317    Element.inflateWidget
package:flutter/…/widgets/framework.dart:3662
#318    MultiChildRenderObjectElement.inflateWidget
package:flutter/…/widgets/framework.dart:6285
#319    Element.updateChild
package:flutter/…/widgets/framework.dart:3414
#320    RenderObjectElement.updateChildren
package:flutter/…/widgets/framework.dart:5717
#321    MultiChildRenderObjectElement.update
package:flutter/…/widgets/framework.dart:6308
#322    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#323    ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4657
#324    StatefulElement.performRebuild
package:flutter/…/widgets/framework.dart:4805
#325    Element.rebuild
package:flutter/…/widgets/framework.dart:4322
#326    StatefulElement.update
package:flutter/…/widgets/framework.dart:4837
#327    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#328    ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4657
#329    Element.rebuild
package:flutter/…/widgets/framework.dart:4322
#330    ProxyElement.update
package:flutter/…/widgets/framework.dart:4985
#331    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#332    ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4657
#333    Element.rebuild
package:flutter/…/widgets/framework.dart:4322
#334    ProxyElement.update
package:flutter/…/widgets/framework.dart:4985
#335    _InheritedNotifierElement.update
package:flutter/…/widgets/inherited_notifier.dart:181
#336    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#337    SingleChildRenderObjectElement.update
package:flutter/…/widgets/framework.dart:6154
#338    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#339    ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4657
#340    StatefulElement.performRebuild
package:flutter/…/widgets/framework.dart:4805
#341    Element.rebuild
package:flutter/…/widgets/framework.dart:4322
#342    StatefulElement.update
package:flutter/…/widgets/framework.dart:4837
#343    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#344    SingleChildRenderObjectElement.update
package:flutter/…/widgets/framework.dart:6154
#345    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#346    SingleChildRenderObjectElement.update
package:flutter/…/widgets/framework.dart:6154
#347    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#348    ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4657
#349    Element.rebuild
package:flutter/…/widgets/framework.dart:4322
#350    ProxyElement.update
package:flutter/…/widgets/framework.dart:4985
#351    Element.updateChild
package:flutter/…/widgets/framework.dart:3401
#352    ComponentElement.performRebuild
package:flutter/…/widgets/framework.dart:4657
#353    StatefulElement.performRebuild
package:flutter/…/widgets/framework.dart:4805
#354    Element.rebuild
package:flutter/…/widgets/framework.dart:4322
#355    BuildOwner.buildScope
package:flutter/…/widgets/framework.dart:2619
#356    WidgetsBinding.drawFrame
package:flutter/…/widgets/binding.dart:878
#357    RendererBinding._han
#358    SchedulerBinding._invokeFrameCallback
package:flutter/…/scheduler/binding.dart:1143
#359    SchedulerBinding.handleDrawFrame
package:flutter/…/scheduler/binding.dart:1080
#360    SchedulerBinding._handleDrawFrame
package:flutter/…/scheduler/binding.dart:996
#364    _invoke (dart:ui/hooks.dart:163:10)
#365    PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:259:5)
#366    _drawFrame (dart:ui/hooks.dart:126:31)
(elided 3 frames from dart:async)

当我单击错误堆栈中的 ( lib/.../view/result_screen.dart:27 ) 时，它会将我带到屏幕的脚手架。我不确定为什么会这样。

我有一个 HomeWrapper 屏幕，其中包含一些小部件和一个页面视图


void initControllers() {
    Get.put(HomeScreenController());
    Get.put(FirstPageController());
    Get.put(SecondPageController());
    Get.put(ThirdPageController());
    Get.put(FourthPageController());
    Get.put(FifthPageController());
    Get.put(SixthPageController());
    Get.put(SeventhPageController());
    Get.put(EighthPageController());
    Get.put(ResultsController());
  }

  @override
  Widget build(BuildContext context) {
    initControllers();
  return Column(...);

}

在第八页，有一个按钮，执行一个方法来计算结果并导航到结果屏幕

class FinishButton extends StatelessWidget {
  final bool _isValid = Get.find<FirstPageController>().validLandArea;
  @override
  Widget build(BuildContext context) {
    return GetBuilder<ResultsController>(
      builder: (controller) => Padding(
        padding: const EdgeInsets.only(bottom: 20.0),child: CupertinoButton(
          child: Text('Finish'),onPressed: () {
            if (_isValid) {
              controller.clickFinishButton();
              Navigator.pushReplacementNamed(context,ResultScreen.id);
            } else {
              HomeScreenController.to.goToLandArea();
            }
          },color: AppColors.primaryColor,),);
  }
}

在结果页面中，有一个按钮可以让我返回 Root，它将根据用户值（无论他是否登录）返回 HomeWrapper 或 Authetication

CupertinoButton(
                        child: Text('Back to Home'),onPressed: () {
                          Navigator.pushReplacementNamed(context,Root.id);
                        },

当我回到 HomeWrapper 时，所有页面都可以使用它们的控制器正常工作，除非我导航回结果屏幕。

我试图让控制器永久和懒惰地放置，但没有奏效。如果有人可以告诉我问题是什么。

getx控制器使用一次后返回null

如何解决getx控制器使用一次后返回null

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