Flutter custom appbar back function is not being triggered

I have a custom AppBar that has a function which should handle the OnBackPressed of the screen, but unfortunately is not being triggered and dunno why.

Basically I want that on pressing the back button, to leave the current screen.

@override
Widget build(BuildContext context) {
    return Scaffold(
      appBar: ComponentAppBar(
        showGoBackButton: true,
        onGoBackPressed: () => Get.back(),
      ),
      body: Container(),
    );
}

The custom app bar file:

import 'package:flutter/material.dart';

class ComponentAppBar extends StatefulWidget implements PreferredSizeWidget {
  final bool showGoBackButton;
  final Function onGoBackPressed;

  const ComponentAppBar({
    Key? key,
    required this.showGoBackButton,
    required this.onGoBackPressed,
  }) : super(key: key);

  @override
  _ComponentAppBarState createState() => _ComponentAppBarState();

  @override
  Size get preferredSize => const Size.fromHeight(kToolbarHeight);
}

class _ComponentAppBarState extends State<ComponentAppBar> {

  @override
  Widget build(BuildContext context) {
    return AppBar(
      title: Row(
        mainAxisAlignment: MainAxisAlignment.start,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          //           
        ],
      ),
      leading: widget.showGoBackButton
          ? IconButton(
              onPressed: () => widget.onGoBackPressed,
              icon: const Icon(
                Icons.arrow_back,
                color: Colors.black,
              ),
            )
          : Container(),
      automaticallyImplyLeading: false,
      leadingWidth: !widget.showGoBackButton ? 0 : 30,
    );
  }
}

Pretty straight forward, yet, when pressing the back button nothing happens.

What have I debugged:

• Instead of Get.back() use Navigator.pop() – same problem
• Add an output onGoBackPressed: () => { print('testing') } – no output
• Change onPressed: () => widget.onGoBackPressed to onPressed: () => Get.back(), it works
• Change onPressed: () => widget.onGoBackPressed to onPressed: () => { print('test directly in class') }, it works

Also, when using the F5 debug tools, it shows like this, which is very strange:

>Solution :

It’s all about callbacks.
You’re receiving a callback as argument (onGoBackPressed), and you need to execute it in order for it to work. There are two ways for doing this:

onPressed: widget.onGoBackPressed, //This should work since you're assigning directly onGoBackPressed as the callback to be executed by onPressed

onPressed: ()=>widget.onGoBackPressed.call(), //This should work since you're calling onGoBackPressed callback. In other words, you're executing it. Before, you were just referencing it, without actually executing

Tip: I’d recommend you to avoid dynamics when typing arguments. So, I recommend you to type specifically what your onGoBackPressed callback will return. This way:

  final void Function() onGoBackPressed;

Which is the same as

  final VoidCallback onGoBackPressed;

Cheers!