I am using this in PersistentTabView :

onWillPop: (final context) async {
await showDialog(
context: context!,
useSafeArea: true,
builder: (final context) => Container(
height: 50,
width: 50,
color: Colors.white,
child: ElevatedButton(
child: const Text("Close"),
onPressed: () {
Navigator.pop(context);
},
),
),
);
return false;
},

I got this error message:
If you declare the onWillPop function, you will have to handle the back function functionality yourself as your onWillPop function will override the default function.
'package:persistent_bottom_nav_bar/persistent_tab_view.widget.dart':
Failed assertion: line 49 pos 16: 'handleAndroidBackButtonPress && onWillPop == null'

And also if we have to use onwillpop in different screen. How can we use.