是否有关于如何创建绘图应用程序的示例＆amp;重用小部件占据屏幕？是的我知道画廊演示应用程序中有一个示例。然而，这有点厚颜无耻，因为该示例实际上并不替换，设置或更改到不同小部件的路由。
我已经从抽屉项目的onTap事件尝试了一个小部件的新实例。当从抽屉中选择一个项目并弹出/推送旧/新路径时，我尝试在创建这些小部件的新实例时遇到重复的全局键错误
ScheduleHomeWidget scheduleWidget = new ScheduleHomeWidget(onSendFeedback: widget.onSendFeedback,);
SpeakerListWidget speakerWidget = new SpeakerListWidget();
var routes = <String, WidgetBuilder> {
ScheduleHomeWidget.routeName : (BuildContext context) => scheduleWidget,
SpeakerListWidget.routeName : (BuildContext context) => speakerWidget
};
和我的MaterialApp：
return new MaterialApp(
title: kAppTitle,
routes: routes,
home: scheduleWidget,
);
以及启动新路线的代码：
onTap: () {
if (routeName != null) {
Timeline.instantSync('Start Transition', arguments: <String, String>{
'from': '/',
'to': routeName
});
Navigator.pop(context);
Navigator.pushNamed(context, routeName);
}
}
}
在实例化ScheduleHomeWidget或SpeakerListWidget实例化时，我没有指定密钥。也就是说，ScheduleHomeWidget使用的AnimatedList使用GlobalKey<AnimatedListState>
我会看到以下异常：
══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following assertion was thrown building Flexible(flex: 1):
Multiple widgets used the same GlobalKey.
The key [LabeledGlobalKey<AnimatedListState>#d63d7] was used by multiple widgets. The parents of
those widgets were different widgets that both had the following description:
Flexible(flex: 1)
A GlobalKey can only be specified on one widget at a time in the widget tree.
When the exception was thrown, this was the stack:
#0 GlobalKey._debugReserveFor.<anonymous closure> (package:flutter/src/widgets/framework.dart:238:9)
#2 GlobalKey._debugReserveFor (package:flutter/src/widgets/framework.dart:219:12)
#3 Element.updateChild.<anonymous closure> (package:flutter/src/widgets/framework.dart:2524:13)
#5 Element.updateChild (package:flutter/src/widgets/framework.dart:2521:12)
#6 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#7 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#8 ProxyElement.update (package:flutter/src/widgets/framework.dart:3639:5)
#9 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#10 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4066:32)
#11 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4448:17)
#12 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#13 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#14 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#15 ProxyElement.update (package:flutter/src/widgets/framework.dart:3639:5)
#16 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#17 RenderObjectElement.updateChildren (package:flutter/src/widgets/framework.dart:4066:32)
#18 MultiChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4448:17)
#19 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#20 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#21 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#22 ProxyElement.update (package:flutter/src/widgets/framework.dart:3639:5)
#23 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#24 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#25 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#26 StatefulElement.update (package:flutter/src/widgets/framework.dart:3528:5)
#27 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#28 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4340:14)
#29 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#30 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#31 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#32 StatelessElement.update (package:flutter/src/widgets/framework.dart:3453:5)
#33 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#34 SingleChildRenderObjectElement.update (package:flutter/src/widgets/framework.dart:4340:14)
#35 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#36 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#37 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#38 StatefulElement.update (package:flutter/src/widgets/framework.dart:3528:5)
#39 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#40 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#41 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#42 StatefulElement.update (package:flutter/src/widgets/framework.dart:3528:5)
#43 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#44 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#45 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#46 ProxyElement.update (package:flutter/src/widgets/framework.dart:3639:5)
#47 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#48 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#49 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#50 ProxyElement.update (package:flutter/src/widgets/framework.dart:3639:5)
#51 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#52 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#53 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#54 StatefulElement.update (package:flutter/src/widgets/framework.dart:3528:5)
#55 Element.updateChild (package:flutter/src/widgets/framework.dart:2542:15)
#56 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3403:16)
#57 Element.rebuild (package:flutter/src/widgets/framework.dart:3292:5)
#58 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2142:33)
#59 BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding&WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:503:20)
#60 BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:189:5)
#61 BindingBase&SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:688:15)
#62 BindingBase&SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:636:9)
#63 BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/rendering/binding.dart:275:20)
#65 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:366)
#66 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:394)
#67 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:151)
(elided 3 frames from class _AssertionError and package dart:async-patch)
════════════════════════════════════════════════════════════════════════════════════════════════════
Reloaded 9 of 459 libraries in 2,143ms.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 3727 pos 14: '_dependents.isEmpty': is not true.
Another exception was thrown: 'package:flutter/src/widgets/framework.dart': Failed assertion: line 1662 pos 12: '_elements.contains(element)': is not true.`
这个错误看起来像Flutter试图通过它的ID多次向树添加一个小部件。不是真的想这样做。只是希望有两个小部件可以成为屏幕的主要焦点。每次用户从侧栏中选择时，不一定必须创建新的。