“PageView tions.isNotEmpty”：在使用PageController.page生成PageView之前，无法访问它。旋转木马颤动
“PageView tions.isNotEmpty”：在使用PageController.page生成PageView之前，无法访问它。旋转木马颤动
提问于 2020-04-20 17:38:47
我正在尝试调用BottomNavigationBar中的List ((位于build(BuildContext context) Widget外部))。该列表包含一个有状态的Widget (包含一个轮播幻灯片)。所以，每当我重新运行我的项目并滚动页面时，我都会收到这个错误，continuously.It说
E/flutter ( 6022): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: 'package:flutter/src/widgets/page_view.dart': Failed assertion: line 180 pos 7: 'positions.isNotEmpty': PageController.page cannot be accessed before a PageView is built with it.
E/flutter ( 6022): #0 _AssertionError._doThrowNew (dart:core-patch/errors_patch.dart:42:39)
E/flutter ( 6022): #1 _AssertionError._throwNew (dart:core-patch/errors_patch.dart:38:5)
E/flutter ( 6022): #2 PageController.page (package:flutter/src/widgets/page_view.dart:180:7)
E/flutter ( 6022): #3 CarouselState.initState.<anonymous closure> (package:carousel_pro/src/carousel_pro.dart:110:24)
E/flutter ( 6022): #4 _rootRunUnary (dart:async/zone.dart:1192:38)
E/flutter ( 6022): #5 _CustomZone.runUnary (dart:async/zone.dart:1085:19)
E/flutter ( 6022): #6 _CustomZone.runUnaryGuarded (dart:async/zone.dart:987:7)
E/flutter ( 6022): #7 _CustomZone.bindUnaryCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1024:26)
E/flutter ( 6022): #8 _rootRunUnary (dart:async/zone.dart:1196:13)
E/flutter ( 6022): #9 _CustomZone.runUnary (dart:async/zone.dart:1085:19)
E/flutter ( 6022): #10 _CustomZone.bindUnaryCallback.<anonymous closure> (dart:async/zone.dart:1008:26)
E/flutter ( 6022): #11 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398:19)
E/flutter ( 6022): #12 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429:5)
E/flutter ( 6022): #13 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)代码如下
Stack Overflow用户
发布于 2020-09-23 09:20:39
在对PageController执行任何操作之前，您可以检查它是否有任何页面。这样做：
pageController.hasClients ? pageController.page(2) : pagecontroller.initialPage;
如果你复制和粘贴你的代码而不是截图，我会有很大的帮助。
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原文链接：
https://stackoverflow.com/questions/61319340
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