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

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

CodePudding user response：

Future<T?> showDialog

Future<T?> showDialog<T>(

    {required BuildContext context,
    required WidgetBuilder builder,
    bool barrierDismissible = true,

no need for the return

CodePudding user response：

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.