如何在屏幕底部显示文本字段，当您在flutter中单击选项卡时

import 'package:flutter/material.dart';

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

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

class _MyAppState extends State<MyApp> {
  int _currentIndex = 0;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Bottom Navigation Bar'),
        ),
        body: IndexedStack(
          index: _currentIndex,
          children: [
            Center(
              child: Text('Tab 1'),
            ),
            Center(
              child: Text('Tab 2'),
            ),
            Center(
              child: Text('Tab 3'),
            ),
          ],
        ),
        bottomNavigationBar: BottomNavigationBar(
          currentIndex: _currentIndex,
          onTap: (index) {
            setState(() {
              _currentIndex = index;
            });
          },
          items: [
            BottomNavigationBarItem(
              icon: Icon(Icons.home),
              label: 'Tab 1',
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.search),
              label: 'Tab 2',
            ),
            BottomNavigationBarItem(
              icon: Icon(Icons.person),
              label: 'Tab 3',
            ),
          ],
        ),
      ),
    );
  }
}