gistfile1.txt

import 'package:flutter/material.dart';

class TabsDemo extends StatefulWidget {
  TabsDemo({Key key}) : super(key: key);

  @override
  _TabsDemoState createState() => new _TabsDemoState();
}

class _TabsDemoState extends State<TabsDemo> with TickerProviderStateMixin {
  static const List<int> colorShades = const <int>[200, 300, 400, 500, 600, 700];

  MaterialColor _activeColors = Colors.red;
  TabController tabController;

  @override
  void initState() {
    super.initState();
    tabController = new TabController(initialIndex: 0, length: colorShades.length, vsync: this);
  }

  @override
  void dispose() {
    tabController.dispose();
    super.dispose();
  }

  _red() {
    setState(() {
      _activeColors = Colors.red;
    });
  }

  _green() {
    setState(() {
      _activeColors = Colors.green;
    });
  }

  _blue() {
    setState(() {
      _activeColors = Colors.blue;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Flutter Demo'),
        bottom: new TabBar(
          controller: tabController,
          tabs: colorShades.map((int shade) {
            return new Container(
              color: _activeColors.shade600,
              child: new Tab(text: shade.toString()),
            );
          }).toList(),
        ),
      ),
      body: new Column(
        children: <Widget>[
          new Expanded(
            child: new TabBarView(
              controller: tabController,
              children: colorShades.map((int shade) {
                return new Center(
                  child: new Container(
                    width: 50.0,
                    height: 50.0,
                    color: _activeColors[shade],
                  ),
                );
              }).toList(),
            ),
          ),
          new Divider(),
          new ButtonBar(
            children: <Widget>[
              new RaisedButton(child: new Text('red'), onPressed: _red),
              new RaisedButton(child: new Text('green'), onPressed: _green),
              new RaisedButton(child: new Text('blue'), onPressed: _blue),
            ],
          ),
        ],
      ),
    );
  }
}

void main() {
  runApp(new MaterialApp(home: new TabsDemo()));
}