docs: PageView Interactive Example leads to non-nullable error

[imcrisanto]

PROBLEM

const MyApp({Key? key}) : super(key: key);

I have noticed an error with the documentation specifically the PageView Interactive Example which leads to this error

error: This requires the 'non-nullable' language feature to be enabled. (experiment_not_enabled at [examenapp] lib/main.dart:12)

FIX (removing the ? allows my app to run)

const MyApp({Key key}) : super(key: key);

Can anyone from the flutter team verify that this is correct? If this is correct I believe the documentation should be updated to reflect this change. packages/flutter/lib/src/widgets/page_view.dart

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[darshankawar]

Document source: https://api.flutter.dev/flutter/widgets/PageView-class.html#widgets.PageView.1

The null safety version option is selected by default which runs properly, but if we unselect that option, then compile errors related to null safety are shown:

May be after unselecting the null safety version, the example should update accordingly to avoid this error and experience.

A similar issue is with https://flutter.dev/docs/cookbook/navigation/navigate-with-arguments#interactive-example, wherein, it runs after unselecting null safety version, but throws null safety compile errors after selecting the option back,

[imcrisanto]

Hi, @darshankawar thanks for answering my question! I will update my code to reflect the NULL SAFETY change :)

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