No Directionality widget found

Solution 1:

flutter doesn't know whether the text is LTR or RTL, so you need to tell him the textDirection explicitly

new Text("Hello", textDirection: TextDirection.ltr)

or you can just wrap the Text with a Directionality Widget

new Directionality(
          textDirection: TextDirection.ltr,
          child: new Text('Hello')

and the purpuse of that is :

A widget that determines the ambient directionality of text and text-direction-sensitive render objects.

And a Text widget in the scope of a MaterialApp widget does not need to be given an explicit writing direction because The default localization in the widgets and material libraries is LTR

Solution 2:

If you don't use MaterialApp you need to wrap your app into some widgets yourself

import 'dart:ui' as ui;
...
runApp(
    new MediaQuery(
        data: new MediaQueryData.fromWindow(ui.window),
        child: new Directionality(
            textDirection: TextDirection.rtl,
            child: new MyHome())))