flutter-examples/using_bottom_nav_bar/lib/example.dart

// Example: Using bottom navigation bar with tabs
import 'package:flutter/material.dart';
import 'package:using_bottom_nav_bar/tabs/first.dart';
import 'package:using_bottom_nav_bar/tabs/second.dart';
import 'package:using_bottom_nav_bar/tabs/third.dart';

class Example extends StatefulWidget {
  const Example({super.key});

  @override
  ExampleState createState() => ExampleState();
}

// SingleTickerProviderStateMixin is used for animation
class ExampleState extends State<Example> with SingleTickerProviderStateMixin {
  // Create a tab controller
  late TabController controller;

  @override
  void initState() {
    super.initState();

    // Initialize the Tab Controller
    controller = TabController(length: 3, vsync: this);
  }

  @override
  void dispose() {
    // Dispose of the Tab Controller
    controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      // Appbar
      appBar: AppBar(
        // Title
        title: Text("Using Bottom Navigation Bar"),
        // Set the background color of the App Bar
        backgroundColor: Colors.blue,
      ),
      // Set the TabBar view as the body of the Scaffold
      body: TabBarView(
        // Add tabs as widgets
        controller: controller,
        // Add tabs as widgets
        children: <Widget>[FirstTab(), SecondTab(), ThirdTab()],
      ),
      // Set the bottom navigation bar
      bottomNavigationBar: Material(
        // set the color of the bottom navigation bar
        color: Colors.blue,
        // set the tab bar as the child of bottom navigation bar
        child: TabBar(
          tabs: <Tab>[
            Tab(
              // set icon to the tab
              icon: Icon(Icons.favorite),
            ),
            Tab(
              icon: Icon(Icons.adb),
            ),
            Tab(
              icon: Icon(Icons.airport_shuttle),
            ),
          ],
          // setup the controller
          controller: controller,
        ),
      ),
    );
  }
}