Tabbar view for my flutter app is not working

Question

This is my code. Changing tabbar view contents is not changing the contents.

I've tried changing the children of tabbar view to text but still no effect

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Material App',
      home: Scaffold(
        backgroundColor: Colors.white,
        body: SafeArea(
          child: Column(
            children: <Widget>[
              Container(
                height: 60,
                width: 500,
                color: Colors.teal,
                margin: EdgeInsets.fromLTRB(0, 0, 0, 0),
                padding: EdgeInsets.fromLTRB(10, 0, 0, 0),
                child: Text(
                  'Choose Your Topic',
                  textAlign: TextAlign.left,
                  style: TextStyle(
                    fontFamily: 'BalooBhaina2-Regular',
                    fontWeight: FontWeight.normal,
                    fontSize: 35,
                    letterSpacing: 0.5,
                    wordSpacing: 2.0,
                    shadows: [
                      Shadow(
                        blurRadius: 50.0,
                        color: Colors.black,
                        offset: Offset(5.0, 5.0),
                      ),
                    ],
                  ),
                ),
              ),
              Container(
                height: 50,
                width: 800,
                margin: EdgeInsets.fromLTRB(0, 0, 0, 5),
                child: DefaultTabController(
                  length: 4,
                  child: Scaffold(
                    appBar: AppBar(
                      bottom: TabBar(tabs: [
                        Tab(icon: Icon(Icons.touch_app)),
                        Tab(icon: Icon(Icons.directions_bike)),
                        Tab(icon: Icon(Icons.movie)),
                        Tab(icon: Icon(Icons.music_video)),
                      ]),
                    ),
                    body: TabBarView(
                      children: [
                        Icon(Icons.touch_app),
                        Icon(Icons.directions_bike),
                        Icon(Icons.movie),
                        Icon(Icons.music_video),
                      ],
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

Answer 1

You can copy paste run full code below
Step 1: You do not need Scaffold and Appbar
Step 2: You can wrap TabBar and TabBarView with Container

code snippet

Container(
    color: Colors.blue,
    height: 50,
    width: 800,
    margin: EdgeInsets.fromLTRB(0, 0, 0, 5),
    child: TabBar(controller: _tabController, tabs: [
      Tab(icon: Icon(Icons.touch_app)),
      Tab(icon: Icon(Icons.directions_bike)),
      Tab(icon: Icon(Icons.movie)),
      Tab(icon: Icon(Icons.music_video)),
    ]),
  ),
  Expanded(
    child: Container(
      //height: 50,
      //width: 800,
      margin: EdgeInsets.fromLTRB(0, 0, 0, 5),
      child: TabBarView(
        controller: _tabController,
        children: [
          Icon(Icons.touch_app),

working demo

full code

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> with SingleTickerProviderStateMixin {
  TabController _tabController;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(vsync: this, length: 4);
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Material App',
      home: Scaffold(
        backgroundColor: Colors.white,
        body: SafeArea(
          child: Column(
            children: <Widget>[
              Container(
                height: 60,
                width: 500,
                color: Colors.teal,
                margin: EdgeInsets.fromLTRB(0, 0, 0, 0),
                padding: EdgeInsets.fromLTRB(10, 0, 0, 0),
                child: Text(
                  'Choose Your Topic',
                  textAlign: TextAlign.left,
                  style: TextStyle(
                    fontFamily: 'BalooBhaina2-Regular',
                    fontWeight: FontWeight.normal,
                    fontSize: 35,
                    letterSpacing: 0.5,
                    wordSpacing: 2.0,
                    shadows: [
                      Shadow(
                        blurRadius: 50.0,
                        color: Colors.black,
                        offset: Offset(5.0, 5.0),
                      ),
                    ],
                  ),
                ),
              ),
              Container(
                color: Colors.blue,
                height: 50,
                width: 800,
                margin: EdgeInsets.fromLTRB(0, 0, 0, 5),
                child: TabBar(controller: _tabController, tabs: [
                  Tab(icon: Icon(Icons.touch_app)),
                  Tab(icon: Icon(Icons.directions_bike)),
                  Tab(icon: Icon(Icons.movie)),
                  Tab(icon: Icon(Icons.music_video)),
                ]),
              ),
              Expanded(
                child: Container(
                  //height: 50,
                  //width: 800,
                  margin: EdgeInsets.fromLTRB(0, 0, 0, 5),
                  child: TabBarView(
                    controller: _tabController,
                    children: [
                      Icon(Icons.touch_app),
                      Icon(Icons.directions_bike),
                      Icon(Icons.movie),
                      Icon(Icons.music_video),
                    ],
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}