Return of invalid type but don't know why? Flutter/Dart

Question

Hey I am totally new to flutter and lately I've been working on a mobile app which recieves data from the ESP32 via BLE but I got the problem that if I wanna ask the user to disconnect with the device like this:

Future<bool> _onWillPop() {
    return showDialog(
        context: context,
        builder: (context) =>
            new AlertDialog(
              title: Text('Are you sure?'),
              content: Text('Do you want to disconnect device 
              and go back?'),

             actions: <Widget>[
                new ElevatedButton(
                    onPressed: () => 
                      Navigator.of(context).pop(false),
                    child: new Text('No')),
                new ElevatedButton(
                    onPressed: () {
                      disconnectFromDevice();
                      Navigator.of(context).pop(true);
                    },
                    child: new Text('Yes')),
              ],
            ) ??
            false);
  }

It gives me the error warnings:

A value of type 'Future<dynamic>' can't be returned from the method '_onWillPop' because it has a return type of 'Future<bool>'.

The return type 'Object' isn't a 'Widget', as required by the closure's context.

But with my current knowlegde I don't know how to solve my problem. I would be extremly thankful if somebody could help me :) and sorry for any grammar mistakes

Answer 1

The error says that the return type of showDialog is not bool. Instead you can just replace with await and then return the bool.

Below is a code which you can put up.

Future<bool> _onWillPop(BuildContext context) async {
    bool shouldPop = false;
    await showDialog(
        context: context,
        builder: (context) =>
            AlertDialog(
              title: const Text('Are you sure?'),
              content: const Text('Do you want to disconnect device and go back?'),
             actions: <Widget>[
                ElevatedButton(
                    onPressed: () {
                      // shouldPop is already false
                    },
                    child: const Text('No')),
                ElevatedButton(
                    onPressed: () async {
                      await disconnectFromDevice();
                      Navigator.of(context).pop();
                      shouldPop = true;
                    },
                    child: const Text('Yes')),
              ],
            ));
    return shouldPop;
  }

I have changed the code a bit so that it returns false if you don't want to pop and returns true if you want to pop. You can just change the code as per your requirement.