Belki bir fikir verir.

import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage>
    with SingleTickerProviderStateMixin {
  TabController tabController;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    tabController = TabController(length: 3, vsync: this);
  }

  tabBak() {
    tabController.addListener(
      () {
        setState(() {
          tabController.index.toString();
        });
      },
    );
  }

  @override
  final benVeriTabanindanGeldim1 = "Veri Tabanindan Geldim1";
  final benVeriTabanindanGeldim2 = "Veri Tabanindan Geldim2";
  final benVeriTabanindanGeldim3 = "Veri Tabanindan Geldim3";

  yazi() {
    String degisken = "00";
    switch (tabController.index.toString()) {
      case "0":
        {
          degisken = "İlk Başlık Seçildi";
        }
        break;

      case "1":
        {
          degisken = "İkinci Başlık Seçildi";
        }
        break;
      case "2":
        {
          degisken = "Üçüncü Başlık Seçildi";
        }
        break;

      default:
        {
          return degisken = "Başlık Seçilmedi";
        }
        break;
    }
    setState(() {});
    return Text(
      degisken,
      style: TextStyle(fontSize: 48),
    );
  }

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
        bottom: TabBar(controller: tabController, tabs: [
          Tab(
            icon: Icon(Icons.filter_1),
            text: benVeriTabanindanGeldim1,
            child: tabBak(),
          ),
          Tab(
            icon: Icon(Icons.filter_2),
            text: benVeriTabanindanGeldim2,
            child: tabBak(),
          ),
          Tab(
            icon: Icon(Icons.filter_3),
            text: benVeriTabanindanGeldim3,
            child: tabBak(),
          ),
        ]),
      ),
      body: TabBarView(
        controller: tabController,
        children: <Widget>[
          Container(
            color: Colors.greenAccent,
            child: Center(
              child: yazi(),
            ),
          ),
          Container(
            color: Colors.orangeAccent,
            child: Center(
              child: yazi(),
            ),
          ),
          Container(
            color: Colors.redAccent,
            child: Center(
              child: yazi(),
            ),
          ),
        ],
      ),
    );
  }
}