I am trying to build simple TabBar but getting an error missing the concrete implementation of 'State.build' and the declaration 'build isn't referenced' . I have created the controller and trying to change to each tab when pressed on individuals. I have created there tab and provided different function to them. By clicking the Tab it will not change. I donot know where I am getting wrong? Thank you in advance.

import 'package:flutter/material.dart';
import 'homepage.dart';
import 'secondpage.dart';
import 'thirdpage.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  static const appTitle = 'Drawer Demo';

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: appTitle,
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key});
  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  late TabController controller;
  @override
  void initState() {
    super.initState();
    controller = TabController(length: 3, vsync: this);
    controller.addListener(() {
      setState(() {});
    });
  }

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

    @override
    Widget build(BuildContext context) => Scaffold(
          appBar: AppBar(
            leading: Icon(Icons.menu),
            title: Text('Tab ${controller.index   1}'),

            centerTitle: true,
            backgroundColor: Colors.purple,
            elevation: 20,
            //titleSpacing: 0,

            bottom: TabBar(
              controller: controller,
              tabs: const [
                Tab(
                  text: 'Home',
                  icon: Icon(Icons.home),
                ),
                Tab(
                  text: 'Page1',
                  icon: Icon(Icons.star),
                ),
                Tab(
                  text: 'Page2',
                  icon: Icon(Icons.person),
                ),
              ],
            ),
          ),
          body: TabBarView(
            controller: controller,
            children: const [
              HomePage(),
              SecondPage(),
              ThirdPage(),
            ],
          ),
          floatingActionButton: FloatingActionButton(
              child: Icon(Icons.add, size: 32),
              onPressed: () {
                  controller.animateTo(0);
                 }
              ),
        );
   }
}

CodePudding user response：

You should declare _MyHomePageState class inside build widget

Widget build(BuildContext context) {
    // TODO: implement build
    throw UnimplementedError();
} 

But you did inside void dispose() {} Method.