How to deactivate or override the Android "BACK" button, in Flutter?

Question

Asked by Jackpap on August 28, 2017 (source).

Is there a way to deactivate the Android back button when on a specific page?

class WakeUpApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: "Time To Wake Up ?",
      home: new WakeUpHome(),
      routes: <String, WidgetBuilder>{
        '/pageOne': (BuildContext context) => new pageOne(),
        '/pageTwo': (BuildContext context) => new pageTwo(),
      },
    );
  }
}

On pageOne I have a button to go to pageTwo:

new FloatingActionButton(
  onPressed: () {    
    Navigator.of(context).pushNamed('/pageTwo');
  },
)

My problem is that if I press the Back arrow at the bottom of the android screen, I go back to pageOne. I would like this button to not show up at all. Ideally, I would like to have no possible way out of this screen unless the user for example keeps his finger pressed on the screen for 5 seconds. (I am trying to write an App for toddlers, and would like only the parents to be able to navigate out of the particular screen).

Answer

Question answered by Rémi R (source).

The answer is WillPopScope. It will prevent the page from being popped by the system. You'll still be able to use Navigator.of(context).pop()

@override
Widget build(BuildContext context) {
  return new WillPopScope(
    onWillPop: () async => false,
    child: new Scaffold(
      appBar: new AppBar(
        title: new Text("data"),
        leading: new IconButton(
          icon: new Icon(Icons.ac_unit),
          onPressed: () => Navigator.of(context).pop(),
        ),
      ),
    ),
  );
}
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