Dynamic Tabs + extendBody

main.dart

import 'package:flutter/material.dart';
import 'dart:math';

void main() => runApp(
  MaterialApp(
      home: MyHomePage(),
    )
);

enum Mode{default_, custom}

const cntrlMode = Mode.default_;

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

  @override
  _MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {
  
  TabController _tabcontroller;
  List<int> _tabs = [1];
 
  @override
  void initState() {
    _tabcontroller = (cntrlMode==Mode.custom) 
      ? TabController(vsync: this, length: _tabs.length, )
      : null;
    super.initState();
  }

  @override
  void dispose() {
    _tabcontroller?.dispose();
    super.dispose();
  }

  void _incrementTabs() {
    setState(() {
      _tabs.add(_tabs.last+1);

      //Cannot use this
      //if (cntrlMode==Mode.custom) _tabcontroller = TabController(vsync: this, length: _tabs.length), );
      
      _tabcontroller = _tabcontroller?.copyWith(length: _tabs.length); //I've made copyWith public in flutter
    });
  }

  void _decrementTabs(element) {
    if (_tabs.length==1)
      return;

    setState(() {
       
      _tabs.remove(element);

      //Cannot use this
      // if (cntrlMode==Mode.custom) {
      //   _tabcontroller = TabController(vsync: this, 
      //     length: _tabs.length,
      //   ) 
      //   ..index = min(_tabs.length-1, _tabcontroller.index);
      // }

      _tabcontroller = _tabcontroller?.copyWith( //I've made copyWith public in flutter
        length: _tabs.length, 
        index: min(_tabs.length-1, _tabcontroller.index),
        previousIndex: min(_tabs.length-1, _tabcontroller.previousIndex),
      );

    });
  }

  _getScafold() => Scaffold(
    appBar: AppBar(
      title: Text("Dynamic Tabs"),
      bottom: TabBar(
        isScrollable: true,
        tabs: _tabs.map<Widget>((tab)=>Tab(icon: Icon(Icons.star), text: "$tab")).toList(),
        controller: _tabcontroller, //null if Mode.default_
      ),
    ),

    body: TabBarView(
      controller: _tabcontroller, //null if Mode.default_
      children: _tabs.map<Widget>((tab)=> 
        Center(child: RaisedButton(
          child: Text("Remove Tab $tab"), 
          onPressed: () => _decrementTabs(tab),
        ),),
      ).toList(),
    ),
    
    extendBody: true, //Show body behind notch

    floatingActionButton: FloatingActionButton(
      onPressed: _incrementTabs,
      child: Icon(Icons.add),
    ),
  );

  @override
  Widget build(BuildContext context) {

    return cntrlMode==Mode.default_ 
      ? DefaultTabController(
          length: _tabs.length,
          child: _getScafold(),
        )
      : _getScafold();

  }
}