"Flutter iOS Back Swipe 不调用 onWillPop"

Question

I covered my Scaffold with a WillPopScope , but the onWillPop callback is not called when swiping to go back on iOS.
What could be the reason for this?

@override
Widget build(BuildContext context) {
  return WillPopScope(
    onWillPop: () async {
      print("onWillPop"); // is not printed to the console
      if (Navigator.of(context).userGestureInProgress)
        return false;
      else
        return true;
    },
    child: new Scaffold(
      appBar: new AppBar(
        title: new Text("App Title"),
      ),
      body: Stack(
        children: <Widget>[
          ...widgets...
        ],
      ),
    ),
  );
}

Answer 1

I found the reason: WillPopScope does not work because the widget with the above build method is not a top widget (the widget called by main). I hope it helps others.

Answer 2

this is a problem and discussed a lot in this issue but there is a way to fix it and it is to use this package

return ConditionalWillPopScope(
child: _MyScreenContent(),
onWillPop: _onWillPop,
shouldAddCallbacks: _hasChanges,
 );

Answer 3

As it is mentioned here here<\/a> , to make your WillPopScope<\/strong> work, you should override hasScopedWillPopCallback<\/strong> getter in MaterialPageRoute<\/strong> like this:

class CustomMaterialPageRoute extends MaterialPageRoute {
  @protected
  bool get hasScopedWillPopCallback {
    return false;
  }
  CustomMaterialPageRoute({
    @required WidgetBuilder builder,
    RouteSettings settings,
    bool maintainState = true,
    bool fullscreenDialog = false,
  }) : super(
          builder: builder,
          settings: settings,
          maintainState: maintainState,
          fullscreenDialog: fullscreenDialog,
        );
}