I create a WillPopScope Function for exit pop service. When user click on back button it's show a dialog for exit permission.

It worked on flutter version 1 perfectly. Now now for null issue, it's create a problem.

Here is my code :

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class ExitPopUp extends StatelessWidget {
  final page;
  ExitPopUp(this.page);
  @override
  Widget build(BuildContext context) {
    Future<bool?> showExitPopUp() {
      return showDialog(
          context: context,
          builder: (BuildContext context) {
            return AlertDialog(
              shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.all(Radius.circular(20.0))),
              backgroundColor: Color.fromRGBO(0, 68, 69, .5),
              title: Text("Confirm", style: TextStyle(color: Colors.white)),
              content: Text("Do you want to Exit ?",
                  style: TextStyle(color: Colors.white)),
              actions: <Widget>[
                ElevatedButton(
                    child: Text(
                      "No",
                      style: TextStyle(color: Colors.yellow[100]),
                    ),
                    onPressed: () {
                      Navigator.pop(context, false);
                    }),
                ElevatedButton(
                    child: Text("Yes",
                        style: TextStyle(color: Colors.yellow[100])),
                    onPressed: () {
                      SystemNavigator.pop();
                    })
              ],
            );
          });
    }

    return WillPopScope(child: page, onWillPop: showExitPopUp);
  }
}

but here is a issue on onWillPop.

How can I fix this issue ?

CodePudding user response：

You can chnage your WillPopScope to this:

return WillPopScope(child: page, onWillPop: () => showExitPopUp().then(b -> b ?? false));

Or you can change your showExitPopUp from Future<bool?> to Future<bool>.

CodePudding user response：

I just convert it to async function. And it's worked here is updated code

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class ExitPopUp extends StatelessWidget {
  final page;
  ExitPopUp(this.page);
  @override
  Widget build(BuildContext context) {
    Future<bool> showExitPopUp() async {
      return await showDialog(
          context: context,
          builder: (BuildContext context) {
            return AlertDialog(
              shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.all(Radius.circular(20.0))),
              backgroundColor: Color.fromRGBO(0, 68, 69, .5),
              title: Text("Confirm", style: TextStyle(color: Colors.white)),
              content: Text("Do you want to Exit ?",
                  style: TextStyle(color: Colors.white)),
              actions: <Widget>[
                ElevatedButton(
                    child: Text(
                      "No",
                      style: TextStyle(color: Colors.yellow[100]),
                    ),
                    onPressed: () {
                      Navigator.pop(context, false);
                    }),
                ElevatedButton(
                    child: Text("Yes",
                        style: TextStyle(color: Colors.yellow[100])),
                    onPressed: () {
                      SystemNavigator.pop();
                    })
              ],
            );
          });
    }

    return WillPopScope(child: page, onWillPop: showExitPopUp);
  }
}