LateInitializationError：字段“_instance@99075166”尚未初始化

Question

这是我第一次测试 flutter 应用程序。HomeView我尝试用这个测试代码来泵：

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void main() {\n  group('Home Test', () {\n    _pumpHome(WidgetTester tester) => tester.pumpWidget(\n          MaterialApp(\n            home: HomeView(),\n          ),\n        );\n\n    testWidgets('Route to Azkar page', (WidgetTester tester) async {\n      await _pumpHome(tester);\n      await tester.tap(find.byKey(Key('morning')));\n      expect(find.byType(ListView), findsOneWidget);\n    });\n  });\n}\n

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但这两个例外却发生了。

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\xe2\x95\x90\xe2\x95\x90\xe2\x95\xa1 EXCEPTION CAUGHT BY WIDGETS LIBRARY \xe2\x95\x9e\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\nThe following LateError was thrown building HomeView(dirty):\nLateInitializationError: Field '_instance@99075166' has not been initialized.\n\nThe relevant error-causing widget was:\n  HomeView file:///E:/projects/flutterProject/tafra/test/home_test.dart:26:19\n\nWhen the exception was thrown, this was the stack:\n#0      ScreenUtil._instance (package:flutter_screenutil/screen_util.dart)\n#1      new ScreenUtil (package:flutter_screenutil/screen_util.dart:28:12)\n#2      SizeExtension.w (package:flutter_screenutil/size_extension.dart:5:19)\n#3      HomeView.build (package:tafra/app/modules/home/views/home_view.dart:23:27)\n#4      StatelessElement.build (package:flutter/src/widgets/framework.dart:4648:28)\n#5      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4574:15)\n#6      Element.rebuild (package:flutter/src/widgets/framework.dart:4267:5)\n#7      ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4553:5)\n#8      ComponentElement.mount (package:flutter/src/widgets/framework.dart:4548:5)\n...     Normal element mounting (166 frames)\n#174    Element.inflateWidget (package:flutter/src/widgets/framework.dart:3611:14)\n#175    MultiChildRenderObjectElement.inflateWidget (package:flutter/src/widgets/framework.dart:6221:36)\n#176    MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:6232:32)\n...     Normal element mounting (354 frames)\n#530    Element.inflateWidget (package:flutter/src/widgets/framework.dart:3611:14)\n#531    Element.updateChild (package:flutter/src/widgets/framework.dart:3360:20)\n#532    RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:1189:16)\n#533    RenderObjectToWidgetElement.update (package:flutter/src/widgets/binding.dart:1167:5)\n#534    RenderObjectToWidgetElement.performRebuild (package:flutter/src/widgets/binding.dart:1181:7)\n#535    Element.rebuild (package:flutter/src/widgets/framework.dart:4267:5)\n#536    BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2582:33)\n#537    AutomatedTestWidgetsFlutterBinding.drawFrame (package:flutter_test/src/binding.dart:1106:19)\n#538    RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:328:5)\n#539    SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1144:15)\n#540    SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1082:9)\n#541    AutomatedTestWidgetsFlutterBinding.pump.<anonymous closure> (package:flutter_test/src/binding.dart:973:9)\n#544    TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:71:41)\n#545    AutomatedTestWidgetsFlutterBinding.pump (package:flutter_test/src/binding.dart:960:27)\n#546    WidgetTester.pumpWidget.<anonymous closure> (package:flutter_test/src/widget_tester.dart:534:22)\n#549    TestAsyncUtils.guard (package:flutter_test/src/test_async_utils.dart:71:41)\n#550    WidgetTester.pumpWidget (package:flutter_test/src/widget_tester.dart:531:27)\n#551    main.<anonymous closure>._pumpHome (file:///E:/projects/flutterProject/tafra/test/home_test.dart:19:46)\n#552    main.<anonymous closure>.<anonymous closure> (file:///E:/projects/flutterProject/tafra/test/home_test.dart:31:22)\n#553    main.<anonymous closure>.<anonymous closure> (file:///E:/projects/flutterProject/tafra/test/home_test.dart:30:40)\n#554    testWidgets.<anonymous closure>.<anonymous closure> (package:flutter_test/src/widget_tester.dart:156:29)\n<asynchronous suspension>\n<asynchronous suspension>\n(elided 5 frames from dart:async and package:stack_trace)\n\n\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\xa1 EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK \xe2\x95\x9e\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\xe2\x95\x90\nThe following assertion was thrown running a test:\nThe finder "zero widgets with key [<'morning'>] (ignoring offstage widgets)" (used in a call to\n"tap()") could not find any matching widgets.\n\nWhen the exception was thrown, this was the stack:\n#0      WidgetController._getElementPoint (package:flutter_test/src/controller.dart:897:7)\n#1      WidgetController.getCenter (package:flutter_test/src/controller.dart:836:12)\n#2      WidgetController.tap (package:flutter_test/src/controller.dart:271:18)\n#3      main.<anonymous closure>.<anonymous closure> (file:///E:/projects/flutterProject/tafra/test/home_test.dart:32:20)\n<asynchronous suspension>\n<asynchronous suspension>\n(elided one frame from package:stack_trace)\n

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我认为第二个例外的原因就是第一个例外。

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我的HomeView生产代码：

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class HomeView extends GetView<HomeController> {\n  @override\n  Widget build(BuildContext context) {\n    return Scaffold(\n      drawer: Drawer(\n        key: Key('drawer'),\n        child: Column(\n          children: [\n            Image.asset(\n              AppUi.assets.logo,\n              height: 600.w,\n              width: Get.width,\n              fit: BoxFit.cover,\n            ),\n            DrawerListTile('\xd8\xa7\xd9\x84\xd8\xa3\xd8\xb3\xd8\xa6\xd9\x84\xd8\xa9', Icons.question_answer, () {\n              Get.back();\n              Get.toNamed(Routes.QUESTIONS);\n            })\n          ],\n        ),\n      ),\n      backgroundColor: AppUi.colors.appSkyLight,\n      appBar: TafraAppBar(\n        titleText: '\xd8\xa7\xd9\x84\xd8\xb1\xd8\xa6\xd9\x8a\xd8\xb3\xd9\x8a\xd8\xa9',\n      ),\n      body: Column(\n        mainAxisAlignment: MainAxisAlignment.center,\n        children: [\n          Row(\n            mainAxisAlignment: MainAxisAlignment.spaceAround,\n            children: [\n              AzkarCard(\n                '\xd8\xa3\xd8\xb0\xd9\x83\xd8\xa7\xd8\xb1 \xd8\xa7\xd9\x84\xd8\xb5\xd8\xa8\xd8\xa7\xd8\xad',\n                Icons.wb_sunny,\n                onTap: () => controller.routeToAzkar(AzkarType.morning),\n                key: Key('morning'),\n              ),\n              AzkarCard(\n                '\xd8\xa3\xd8\xb0\xd9\x83\xd8\xa7\xd8\xb1 \xd8\xa7\xd9\x84\xd9\x85\xd8\xb3\xd8\xa7\xd8\xa1',\n                Icons.nightlight_round,\n                onTap: () => controller.routeToAzkar(AzkarType.evening),\n                key: Key('evening'),\n              ),\n            ],\n          ),\n        ],\n      ),\n    );\n  }\n}\n

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和是DrawerListTile自AzkarCard定义小部件。当我删除它们并将它们与Text小部件交换时，测试代码成功了！

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所以我不知道我想测试的代码是否不应该有自定义小部件。这在实际项目中是不可能的。

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Answer 1

问题已经解决了！

ScreenUtilInit中缺少此问题的原因MaterialApp。方法pumpWidget应该是这样的：

_pumpWidget(WidgetTester tester,) => tester.pumpWidget(
        MaterialApp(
          home: ScreenUtilInit(
              designSize: Size(1080, 1920), builder: () => HomeView()),
        ),
      );