Flutter/Dart - 延迟后打开视图

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【中文标题】Flutter/Dart - 延迟后打开视图【英文标题】：Flutter/Dart - Open a view after a delay 【发布时间】：2018-08-10 21:28:09 【问题描述】：

我正在尝试在加载视图延迟后找到打开视图的解决方案。我有一个视图，其中有一个按钮，当我按下它时，onPressed() 方法会触发一个Navigator.of(Context).pushNamed("/loading")。打开加载视图。在加载视图中，我有一个功能可以延迟 1.5 秒，然后打开主视图，代码如下：

Future delay() async
await new Future.delayed(new Duration(milliseconds: 1500), ()

   Navigator.of(context).pushNamed("/home");

但是，当延迟开始时，1.5 秒后，它会打开主视图，但有以下例外：

I/flutter ( 5226): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter ( 5226): The following assertion was thrown building IconTheme(color: Color(0xff000000)):
I/flutter ( 5226): Multiple widgets used the same GlobalKey.
I/flutter ( 5226): The key [LabeledGlobalKey<ScaffoldState>#a0051] was used by multiple widgets. The parents of those
I/flutter ( 5226): widgets were different widgets that both had the following description:
I/flutter ( 5226):   IconTheme(color: Color(0xff000000))
I/flutter ( 5226): A GlobalKey can only be specified on one widget at a time in the widget tree.
I/flutter ( 5226): When the exception was thrown, this was the stack:
I/flutter ( 5226): #0      GlobalKey._debugReserveFor.<anonymous closure> (package:flutter/src/widgets/framework.dart:172:9)
I/flutter ( 5226): #1      GlobalKey._debugReserveFor (package:flutter/src/widgets/framework.dart:182:6)
I/flutter ( 5226): #2      Element.updateChild.<anonymous closure> (package:flutter/src/widgets/framework.dart:2649:13)
I/flutter ( 5226): #3      Element.updateChild (package:flutter/src/widgets/framework.dart:2652:6)
I/flutter ( 5226): #4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #5      Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #6      ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #7      ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #8      Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #9      Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #10     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #11     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #12     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #13     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #14     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #15     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #16     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #17     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #18     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #19     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #20     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #21     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #22     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #23     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #24     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #25     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #26     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #27     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #28     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #29     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #30     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #31     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #32     ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3893:16)
I/flutter ( 5226): #33     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #34     MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4693:32)
I/flutter ( 5226): #35     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #36     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #37     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #38     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #39     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #40     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #41     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #42     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #43     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #44     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #45     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #46     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #47     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #48     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #49     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #50     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #51     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #52     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #53     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #54     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #55     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #56     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #57     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #58     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #59     SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #60     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #61     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #62     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #63     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #64     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #65     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #66     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #67     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #68     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #69     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #70     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #71     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #72     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #73     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #74     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #75     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #76     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #77     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #78     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #79     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #80     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #81     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #82     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #83     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #84     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #85     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #86     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #87     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #88     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #89     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #90     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #91     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #92     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #93     Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #94     Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #95     ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #96     Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #97     ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #98     StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #99     ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #100    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #101    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #102    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #103    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #104    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #105    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #106    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #107    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #108    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #109    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #110    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #111    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #112    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #113    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #114    SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #115    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #116    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #117    SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #118    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #119    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #120    SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #121    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #122    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #123    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #124    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #125    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #126    StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #127    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #128    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #129    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #130    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #131    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #132    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #133    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #134    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #135    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #136    SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #137    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #138    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #139    SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #140    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #141    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #142    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #143    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #144    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #145    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
E/flutter ( 5226): [ERROR:topaz/lib/tonic/logging/dart_error.cc(16)] Unhandled exception:
E/flutter ( 5226): NoSuchMethodError: The method 'ancestorStateOfType' was called on null.
E/flutter ( 5226): Receiver: null
E/flutter ( 5226): Tried calling: ancestorStateOfType(Instance of 'TypeMatcher<NavigatorState>')
E/flutter ( 5226): #0      Object.noSuchMethod (dart:core-patch/dart:core/object_patch.dart:46)
E/flutter ( 5226): #1      Navigator.of (package:flutter/src/widgets/navigator.dart:722:19)
E/flutter ( 5226): #2      Navigator.pushReplacementNamed (package:flutter/src/widgets/navigator.dart:666:22)
E/flutter ( 5226): #3      switcher (package:ticketing/router.dart:53:13)
E/flutter ( 5226): #4      _LoadingViewState.switchView (/data/user/0/com.tiziano.flutterapp.flutterapp2/cache/ticketing_remasteredAHSWSC/ticketing_remastered/lib/view/loadingview/LoadingView.dart:79:3)
E/flutter ( 5226): #5      _LoadingViewState.delay.<anonymous closure> (/data/user/0/com.tiziano.flutterapp.flutterapp2/cache/ticketing_remasteredAHSWSC/ticketing_remastered/lib/view/loadingview/LoadingView.dart:74:70)
E/flutter ( 5226): #6      new Future.delayed.<anonymous closure> (dart:async/future.dart:310)
E/flutter ( 5226): #7      Timer._createTimer.<anonymous closure> (dart:async-patch/dart:async/timer_patch.dart:21)
E/flutter ( 5226): #8      _Timer._runTimers (dart:isolate-patch/dart:isolate/timer_impl.dart:367)
E/flutter ( 5226): #9      _Timer._handleMessage (dart:isolate-patch/dart:isolate/timer_impl.dart:401)
E/flutter ( 5226): #10     _RawReceivePortImpl._handleMessage (dart:isolate-patch/dart:isolate/isolate_patch.dart:164)
I/flutter ( 5226): #146    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #147    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #148    SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4588:14)
I/flutter ( 5226): #149    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #150    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #151    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #152    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #153    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #154    StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #155    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #156    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #157    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #158    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #159    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #160    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #161    StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #162    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #163    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #164    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #165    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #166    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #167    ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3582:5)
I/flutter ( 5226): #168    StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3718:22)
I/flutter ( 5226): #169    ComponentElement.mount (package:flutter/src/widgets/framework.dart:3577:5)
I/flutter ( 5226): #170    Element.inflateWidget (package:flutter/src/widgets/framework.dart:2875:14)
I/flutter ( 5226): #171    Element.updateChild (package:flutter/src/widgets/framework.dart:2678:12)
I/flutter ( 5226): #172    RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4375:32)
I/flutter ( 5226): #173    MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4703:17)
I/flutter ( 5226): #174    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #175    _TheatreElement.update (package:flutter/src/widgets/overlay.dart:507:16)
I/flutter ( 5226): #176    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #177    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #178    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #179    StatefulElement.update (package:flutter/src/widgets/framework.dart:3737:5)
I/flutter ( 5226): #180    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #181    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #182    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #183    ProxyElement.update (package:flutter/src/widgets/framework.dart:3847:5)
I/flutter ( 5226): #184    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #185    SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4595:14)
I/flutter ( 5226): #186    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #187    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #188    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #189    StatefulElement.update (package:flutter/src/widgets/framework.dart:3737:5)
I/flutter ( 5226): #190    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #191    SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4595:14)
I/flutter ( 5226): #192    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #193    SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4595:14)
I/flutter ( 5226): #194    Element.updateChild (package:flutter/src/widgets/framework.dart:2667:15)
I/flutter ( 5226): #195    ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3613:16)
I/flutter ( 5226): #196    Element.rebuild (package:flutter/src/widgets/framework.dart:3463:5)
I/flutter ( 5226): #197    BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2210:33)
I/flutter ( 5226): #198    BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:621:20)
I/flutter ( 5226): #199    BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:208:5)
I/flutter ( 5226): #200    BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:990:15)
I/flutter ( 5226): #201    BindingBase&GestureBinding&ServicesBinding&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:930:9)
I/flutter ( 5226): #202    BindingBase&GestureBinding&ServicesBinding&SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:842:5)
I/flutter ( 5226): #203    _invoke (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:120)
I/flutter ( 5226): #204    _drawFrame (file:///b/build/slave/Linux_Engine/build/src/flutter/lib/ui/hooks.dart:109)
I/flutter ( 5226): ════════════════════════════════════════════════════════════════════════════════════════════════════
I/flutter ( 5226): Another exception was thrown: Multiple widgets used the same GlobalKey.

顺便说一句，在主视图中没有任何黑色图标。 （图标主题（颜色：颜色（0xff000000）） 有人可以帮忙吗？

【问题讨论】：

可能在两个小部件中多次使用单个键？没有代码很难说更多。关键参考 - docs.flutter.io/flutter/widgets/Widget/key.html 在主视图中，如果我在没有通过加载视图的情况下打开它，我没有任何异常。即使我的加载视图为空白，1.5 秒后总会出现异常。但是，我从未将 key 参数用于任何小部件声明。 小部件的更好的邮政编码 【参考方案1】：

如果你只是想延迟代码执行，那么你必须使用 await（没有它就行不通）

print('Before delay: $DateTime.now()');
await Future.delayed(const Duration(milliseconds: 1500));
print('After delay: $DateTime.now()');

【讨论】：

【参考方案2】： 
    ontab: () 
        Future.delayed(Duration(seconds: 5), () 
            Center(child: CircularProgressIndicator(color: kpurple));
            Navigator.of(context).pushNamed('/Home');
        );
    ,

循环进度指示器不工作

【讨论】：

【参考方案3】：

您可以通过两种方式做到这一点：

    使用Timer 类。

    import 'dart:async';

Timer(Duration(seconds: 5), () 
  // 5 seconds over, navigate to Page2.
  Navigator.push(context, MaterialPageRoute(builder: (_) => Screen2()));
);

    使用Future.delayed 类：

    Future.delayed(Duration(seconds: 5), () 
  // 5 seconds over, navigate to Page2.
  Navigator.push(context, MaterialPageRoute(builder: (_) => Screen2()));
);

使用Future 优于Timer 的优点是可以取消它。

【讨论】：

@CopsOnRoad CopsOnRoad - 我正在尝试使用 Future.delayed(Duration(seconds: 10 / 2), () .... 和 10/2 在 Duration 秒内不起作用。请建议它的解决方案是什么。谢谢。 @Kamlesh seconds 接受int，而10/2 是double，您应该改用10~/2。【参考方案4】：

你可以这样使用；

Future myFuture() async 

await new Future.delayed(new Duration(seconds: 3));

//return your_main_future_code_here;

【讨论】：

【参考方案5】：

在 android 开发中，我们使用 postDelayed() 回调来保持屏幕。但在 Flutter 中，这非常棘手，因为在 Flutter 中有 async 方法可以执行此类任务。

首先，像这样添加一个从 StatefulWidget 扩展的类。

class SplashScreen extends StatefulWidget 
  @override                         
  State<StatefulWidget> createState() 
    return SplashState();
  


class SplashState extends State<SplashScreen> 
  @override
  void initState() 
    // TODO: implement initState
    super.initState();
    startTime();
  
  
  @override
  Widget build(BuildContext context) 
    return Scaffold(
      body: initScreen(context),
    );

它将覆盖initState 和build 方法。在initState 方法中，我们通过在此处添加这些行来添加延迟功能。

startTime() async 
  var duration = new Duration(seconds: 6);
  return new Timer(duration, route);

startTime 方法是在后台执行任务的async 方法。我们为此使用Timer 类，我们通过持续时间来保持屏幕和route/designation 来指示去哪里。我们使用Navigator 来设置路线/指定。这是代码。

对于 Timer 类，请导入此文件。

import 'dart:async';

这里是完整的代码

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:screens/SecondScreen';                                               
class SplashScreen extends StatefulWidget 
  @override
  State<StatefulWidget> createState() 
    return SplashState();

class SplashState extends State<SplashScreen> 
  @override
  void initState() 
    // TODO: implement initState
    super.initState();
    startTime();
  
  
  @override
  Widget build(BuildContext context) 
    return Scaffold(
      body: initScreen(context),
    );
  
  
  startTime() async 
    var duration = new Duration(seconds: 6);
    return new Timer(duration, route);
  
route() 
    Navigator.pushReplacement(context, MaterialPageRoute(
        builder: (context) => SecondScreen()
      )
    ); 
  
  
  initScreen(BuildContext context) 
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Container(
              child: Image.asset("images/logo.png"),
            ),
            Padding(padding: EdgeInsets.only(top: 20.0)),
            Text(
              "Splash Screen",
              style: TextStyle(
                fontSize: 20.0,
                color: Colors.white
              ),
            ),
            Padding(padding: EdgeInsets.only(top: 20.0)),
            CircularProgressIndicator(
              backgroundColor: Colors.white,
              strokeWidth: 1,
           )
         ],
       ),
      ),
    );

更多信息请见：https://medium.com/codechai/lunching-other-screen-after-delay-in-flutter-c9ebf4d7406e

【讨论】：

我正在尝试使用 Future.delayed(Duration(seconds: 10 / 2), () .... 和 10/2 在 Duration 秒内不起作用。请建议它的解决方案是什么？谢谢。【参考方案6】：

要在延迟后打开视图，您可以使用Future.delayed：

Future.delayed(const Duration(milliseconds: 500), () 
  setState(() 
    // Here you can write your code for open new view
  );
);

希望对你有所帮助。

【讨论】：

【参考方案7】：

使用dart:async 库中的Future.delay 构造函数，在单击RaisedButton 3 秒后，以下代码从第一页导航到第二页，我不明白你为什么要推动 加载 查看？

import 'dart:async';

class FirstView extends StatelessWidget 
  @override
  Widget build(BuildContext context) 
    return new Scaffold(
      body: new Center(
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          crossAxisAlignment: CrossAxisAlignment.center,
          children: <Widget>[
            new Text("FIRST VIEW"),
            new RaisedButton(
              onPressed: () async 
                await new Future.delayed(const Duration(seconds: 3));
                Navigator.push(context, new MaterialPageRoute(builder: (__) => new SecondView()));
              ,
              child: new Text("Go to 2nd view"),
            )
          ],
        ),
      ),
    );
  


class SecondView extends StatelessWidget 
  @override
  Widget build(BuildContext context) 
    return new Scaffold(
      body: new Center(
        child: new Text("SECOND VIEW"),
      ),
    );

【讨论】：

我登录后，应用显示加载视图，然后它应该会自动更改视图，无需按下按钮。 我不明白你想做什么？？ 我只想在登录后和应用程序启动前显示一个加载动画。所以当我打开app有一个登录表单，如果我登录有这个视图显示动画，然后自动进入首页。 @ShadyAziza - 我正在尝试使用 Future.delayed(Duration(seconds: 10 / 2), () .... 和 10/2 在 Duration 秒内不起作用。请建议它的解决方案是什么？谢谢。

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