flutter - android back button does not call onWillPop of WillPopScope

Issue

I would like to exit my application. I have implemented a WillPopScope, but it looks like the onWillPop function is not being called at all. I tried many things like swap WillPopScope with Scaffold, changing the return value of the function, but it just looks like it is not working as expected.

My code:

Future<bool> _willPopCallback() async {
  exit(0);
  // await showDialog or Show add banners or whatever
  // then
  return true; // return true if the route to be popped
}


return Scaffold(
    appBar: MyAppBar(
      leading: DrawerAction(),
      title: Text(AppLocalizations.of(context).textCapitalized('home_page')),
      onSearch: (searchTerms) => this.search(searchTerms, context),
    ),
    body: new WillPopScope(
      onWillPop: _willPopCallback, // Empty Function.
      child: //my screen widgets

I am not sure if this is a bug I should report to flutter or I am doing something wrong. Happy to provide more code on request.

I have tried:

exit(0);
Navigator.of(context).pop();
SystemChannels.platform.invokeMethod('SystemNavigator.pop');

Thanks in advance!

Solution

I managed to solve my problem and I think it is a very particular case, but it still might be helpful to someone.

TL;DR: Ensure that you dont have multiple Scaffolds in your widgets

I was using IndexedStack in my menu navigator, obviously wrapped with a Scaffold. The pages of the stack had Scaffold as well, and with this combination WillPopScope was not working neither in the navigator page neither in its stack pages. I solved by removing all the Scaffolds in the stack pages and having only one in the controller. In this way I managed to use WillPopScope correctly.

Answered By - Gicminos