Bottom Navigation bar with centered button group

I am trying to create a Bottom Navigation Bar with a button group in the middle. The 2 icons on either side of the button group will switch the displayed screen. The centered button group has 3 buttons which would act on the displayed screen. This is similar to the new Google Assistant bottom bar

.

I tried using the BottomNavigationBar with the centre item a custom widget. However the sizes of all the items end up equal. Any help creating this layout would be appreciated. Thanks.

This is the design I am trying to achieve

Here’s what I have now:

  @override
  Widget build(BuildContext context) {
    return WillPopScope(
      onWillPop: () async => false,
      child: Scaffold(
          appBar: AppBar(
            backgroundColor: Theme.of(context).colorScheme.primary,
            foregroundColor: Theme.of(context).colorScheme.secondary,
            leading: IconButton(
              icon: Image.asset(alInvertedIcon, width: 32, semanticLabel: "Home screen"),
              onPressed: () {
                push(const HomeScreen());
              },
              iconSize: 32,
            ),
            title: Image.asset(alTextInv, width: 175),
            centerTitle: true,
            actions: [
              IconButton(
                icon: const Icon(Icons.person_outlined, semanticLabel: "User Profile"),
                onPressed: () {
                  push(const ProfileScreen());
                },
                iconSize: 32,
              )
            ],
          ),
          body: bodyWidget,
          bottomNavigationBar: BottomNavigationBar(
            type: BottomNavigationBarType.fixed,
            onTap: _onItemTapped,
            showSelectedLabels: false,
            showUnselectedLabels: false,
            backgroundColor: Theme.of(context).colorScheme.secondary,
            selectedItemColor: Theme.of(context).colorScheme.primary,
            unselectedItemColor: Colors.grey,
            currentIndex: _currentIndex,
            items: [
              const BottomNavigationBarItem(
                icon: Icon(
                  Icons.camera_alt,
                ),
                label: 'Visual',
              ),
              BottomNavigationBarItem(
                icon: SizedBox(
                  width: 300,
                  child: _actionPanel(),
                ),
                label: 'Add',
              ),
              const BottomNavigationBarItem(
                icon: Icon(
                  Icons.chat,
                ),
                label: 'Text',
              ),
            ],
          ),
      ),
    );
  }

  Widget _actionPanel() {
    return Material(
      elevation: 1.0,
      borderRadius: const BorderRadius.all(Radius.circular(25)),
      child: Row(
        children: <Widget>[
          IconButton(
            onPressed: () {},
            icon: const Icon(
              Icons.refresh,
            ),
          ),
          IconButton(
            onPressed: () {},
            icon: const Icon(
              Icons.mic,
            ),
          ),
          IconButton(
            onPressed: () {},
            icon: const Icon(
              Icons.camera,
            ),
          ),
        ],
      ),
    );
  }

>Solution :

Try using this way.

Widget _actionPanel() {
    return Material(
      elevation: 1.0,
      borderRadius: BorderRadius.all(Radius.circular(25)),
      child: Container(
        padding: EdgeInsets.symmetric(vertical: 3),
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceAround,
          children: [
            MaterialButton(
              onPressed: () {},
              shape: CircleBorder(),
              minWidth: 0,
              padding: EdgeInsets.all(5),
              materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
              child: Icon(Icons.refresh),
            ),
            MaterialButton(
              onPressed: () {},
              shape: CircleBorder(),
              minWidth: 0,
              padding: EdgeInsets.all(5),
              materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
              child: Icon(Icons.mic),
            ),
            MaterialButton(
              onPressed: () {},
              shape: CircleBorder(),
              minWidth: 0,
              padding: EdgeInsets.all(5),
              materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
              child: Icon(Icons.camera),
            ),
          ],
        ),
      ),
    );
  }