The following assertion was thrown building Text(“Deliver features faster”,textAlign: center):
No Directionality widget found.我认为问题可能在TextDirection类属性中,但我一直无法找到它.
这是我的代码：
import 'package:flutter/material.dart'; import 'package:flutter/widgets.dart'; void main(){ runApp( new MyHome()); } class MyHome extends StatelessWidget{ @override Widget build(BuildContext context) { // TODO: implement build return new Material( child: new Container( color: Colors.red,margin: const EdgeInsets.all(5.0),child: new Row( children: <Widget>[ new Expanded( child: new Text('Deliver features faster',textAlign: TextAlign.center),),new Expanded( child: new Text('Craft beautiful UIs',new Expanded( child: new FittedBox( fit: BoxFit.contain,// otherwise the logo will be tiny child: const Flutterlogo(),],) ),); } }以下是错误的完整堆栈跟踪：
The following assertion was thrown building Text("Deliver features faster",textAlign: center): No Directionality widget found. RichText widgets require a Directionality widget ancestor. The specific widget that could not find a Directionality ancestor was: RichText(textAlign: center,softWrap: wrapping at Box width,maxLines: unlimited,text: "Deliver features faster") The ownership chain for the affected widget is: RichText ← Text ← Expanded ← Row ← DecoratedBox ← Padding ← Container ← DefaultTextStyle ← AnimatedDefaultTextStyle ← _InkFeatures-[GlobalKey#978b7 ink renderer] ← ⋯ Typically,the Directionality widget is introduced by the MaterialApp or WidgetsApp widget at the top of your application widget tree. It determines the ambient reading direction and is used,for example,to determine how to lay out text,how to interpret "start" and "end" values,and to resolve EdgeInsetsDirectional,AlignmentDirectional,and other *Directional objects. When the exception was thrown,this was the stack: #0 debugCheckHasDirectionality.<anonymous closure> (package:flutter/src/widgets/debug.dart:223:7) #1 debugCheckHasDirectionality (package:flutter/src/widgets/debug.dart:239:4) #2 RichText.createRenderObject (package:flutter/src/widgets/basic.dart:4245:37) #3 RenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4259:28) #4 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #5 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #6 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #7 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #8 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #9 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #10 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #11 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #12 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #13 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #14 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #15 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #16 ParentDataElement.mount (package:flutter/src/widgets/framework.dart:3938:16) #17 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #18 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4738:32) #19 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #20 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #21 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4633:14) #22 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #23 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #24 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4633:14) #25 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #26 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #27 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #28 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #29 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #30 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #31 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #32 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #33 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #34 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #35 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #36 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #37 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #38 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #39 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #40 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #41 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #42 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3752:22) #43 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #44 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #45 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #46 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4633:14) #47 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #48 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #49 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #50 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #51 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #52 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #53 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #54 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #55 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:4633:14) #56 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #57 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #58 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #59 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #60 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #61 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3752:22) #62 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #63 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #64 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #65 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #66 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #67 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #68 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:3752:22) #69 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #70 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #71 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #72 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:3636:16) #73 Element.rebuild (package:flutter/src/widgets/framework.dart:3478:5) #74 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:3605:5) #75 ComponentElement.mount (package:flutter/src/widgets/framework.dart:3600:5) #76 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2890:14) #77 Element.updateChild (package:flutter/src/widgets/framework.dart:2693:12) #78 RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:852:16) #79 RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:823:5) #80 RenderObjectToWidgetAdapter.attachToRenderTree.<anonymous closure> (package:flutter/src/widgets/binding.dart:769:17) #81 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2205:19) #82 RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:768:13) #83 BindingBase&GestureBinding&ServicesBinding&SchedulerBinding&PaintingBinding&RendererBinding&WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:657:7) #84 runApp (package:flutter/src/widgets/binding.dart:699:7) #85 main (/data/user/0/com.yourcompany.flutterproject/cache/flutter_projectENWZDI/flutter_project/lib/main.dart:6:3) #86 _startIsolate.<anonymous closure> (dart:isolate-patch/dart:isolate/isolate_patch.dart:279) #87 _RawReceivePortImpl._handleMessage (dart:isolate-patch/dart:isolate/isolate_patch.dart:165) ════════════════════════════════════════════════════════════════════════════════════════════════════ Another exception was thrown: No Directionality widget found. Another exception was thrown: Horizontal RenderFlex with multiple children has a null textDirection,so the layout order is undefined. Another exception was thrown: 'package:flutter/src/rendering/Box.dart': Failed assertion: line 1446 pos 12: 'hasSize': is not true. uid=10079(com.yourcompany.flutterproject) Thread-5 identical 2 lines Another exception was thrown: 'package:flutter/src/rendering/Box.dart': Failed assertion: line 1446 pos 12: 'hasSize': is not true. Another exception was thrown: 'package:flutter/src/rendering/proxy_Box.dart': Failed assertion: line 1564 pos 12: 'hasSize': is not true.
new Text("Hello",textDirection: TextDirection.ltr)
或者您可以使用Directionality小部件包装文本
new Directionality(
textDirection: TextDirection.ltr,child: new Text('Hello')
而且它的目的是：
A widget that determines the ambient directionality of text and
text-direction-sensitive render objects.
并且不需要为MaterialApp窗口小部件范围内的文本窗口小部件提供明确的书写方向,因为窗口小部件和材质库中的默认本地化是LTR
