Flutter: No Directionality widget found - dart

Question

I am getting below exception while running flutter code in android studio.
I/flutter ( 5360): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY
╞═══════════════════════════════════════════════════════════ I/flutter
( 5360): The following assertion was thrown building Text("xyz"): I/flutter ( 5360): No Directionality widget found. I/flutter
( 5360): RichText widgets require a Directionality widget ancestor.
I/flutter ( 5360): The specific widget that could not find a
Directionality ancestor was: I/flutter ( 5360): RichText(softWrap:
wrapping at box width, maxLines: unlimited, text: "xyz")
I/flutter ( 5360): The ownership chain for the affected widget is:
I/flutter ( 5360): RichText ← Text ← Center ← Container ← [root]
I/flutter ( 5360): Typically, the Directionality widget is introduced
by the MaterialApp or WidgetsApp widget at the I/flutter ( 5360): top
of your application widget tree. It determines the ambient reading
direction and is used, for I/flutter ( 5360): example, to determine
how to lay out text, how to interpret "start" and "end" values, and to
resolve I/flutter ( 5360): EdgeInsetsDirectional,
AlignmentDirectional, and other *Directional objects.
Code snippet:
import 'package:flutter/material.dart';
void main() {
runApp(
Container(child: Center(child: Text("xyz"))),
);
}
I am not sure why this exception says
I/flutter ( 5360): Typically, the Directionality widget is introduced by the MaterialApp or WidgetsApp widget at the ...
Because in flutter everything is a widget, so any widget should work for us.

Answer 1

If you are using a material widget component, like Scaffold, Material, you don't need to specify textDirection in your Text widget because Directionality is implicitly provided in these cases. So, a good solution would be to use:
Scaffold(body: Text("xyz"))
But if you don't use it, you will have to
Text(
'xyz',
textDirection: TextDirection.ltr,
)

Answer 2

If you are using Directionality constructor your problem will resolve
Widget build(BuildContext context) {
return Directionality(
textDirection: TextDirection.ltr,
child: Container(
color: myColor,
child: Center(
child: RaisedButton(
onPressed: () {
print('You pressed me');
changeColor();
},
child: Text('Click', textDirection: TextDirection.ltr)
),
),
),
);
}

Answer 3

Text widget needs to know whether it should display text left to right or right to left. There is no default. This information can be provided in 2 ways:
by nesting it in Directionality widget (as mentioned in the error message, typically MaterialApp or WidgetsApp)
explicitly, as an argument to the constructor:
Text(
'Hello World',
textDirection: TextDirection.ltr,
)
Second approach clearly is unmanageable in the long run.

Answer 4

late but I hope it can help.
I don't use any predefined root widget too. So I wrapped my App in Directionality widget in main function and flutter stopped complaining:
my code:
void main() {
runApp(
new Directionality(textDirection: TextDirection.ltr, child: MyApp())
);
}

Answer 5

A little more elaboration on what's happening internally.
When a Text widget is used without the specified style, it tries to inherit the style from the parents automatically. Here's the first few lines of the build method of Text Widget.
#override
Widget build(BuildContext context) {
final DefaultTextStyle defaultTextStyle = DefaultTextStyle.of(context);
TextStyle? effectiveTextStyle = style;
if (style == null || style!.inherit)
effectiveTextStyle = defaultTextStyle.style.merge(style);
if (MediaQuery.boldTextOverride(context))
effectiveTextStyle = effectiveTextStyle!.merge(const TextStyle(fontWeight: FontWeight.bold));
Look at the line - final DefaultTextStyle defaultTextStyle = DefaultTextStyle.of(context);
Now if a material widget is used in the widget tree before the Text Widget appears, they would have already set the default text style which Text widget automatically inherits from the Build Context. If none of the material widgets were used before Text, then we would need to specify the text style explicitly.