BehindNavbar example

main.dart

import 'package:flutter/material.dart';

final Color darkBlue = Color.fromARGB(255, 18, 32, 47);

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home:  MyWidget(),
       
     
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
  appBar: AppBar(
    title: Text('title'),
  ),
  floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
  floatingActionButton: FloatingActionButton(
    onPressed: () { },
    tooltip: 'Increment',
    child: Icon(Icons.add),
    elevation: 2.0),
    body: ListView.builder(
              itemCount: 50,
              itemBuilder: (context, index) => Container(
                  height: 100,
                  color: index % 2 == 0 ? Colors.white : Colors.grey.shade900)),
  extendBody: true,
  bottomNavigationBar: BottomAppBar(
    child: Row(
      mainAxisSize: MainAxisSize.max,
      mainAxisAlignment: MainAxisAlignment.spaceBetween,
      children: <Widget>[
        IconButton(icon: Icon(Icons.dangerous), onPressed: (){}),
         IconButton(icon: Icon(Icons.dangerous), onPressed: (){}),
         IconButton(icon: Icon(Icons.dangerous), onPressed: (){}),
         IconButton(icon: Icon(Icons.dangerous), onPressed: (){}),
      ],
    ),
    shape: CircularNotchedRectangle(),
    color: Colors.blueGrey,
  ),
);}
}