仅在构建futurebuilder时显示bottomNavigationBar

import 'package:flutter/material.dart';

class MyPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('My Page'),
      ),
      body: FutureBuilder(
        future: fetchData(), // 异步操作，返回一个Future
        builder: (BuildContext context, AsyncSnapshot snapshot) {
          if (snapshot.connectionState == ConnectionState.waiting) {
            // 当Future正在加载数据时显示加载指示器
            return Center(
              child: CircularProgressIndicator(),
            );
          } else if (snapshot.hasError) {
            // 当Future发生错误时显示错误信息
            return Center(
              child: Text('Error: ${snapshot.error}'),
            );
          } else {
            // 当Future完成时根据数据来构建UI
            return Center(
              child: Text('Data: ${snapshot.data}'),
            );
          }
        },
      ),
      bottomNavigationBar: BottomNavigationBar(
        // 底部导航栏
        items: const <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: 'Home',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.business),
            label: 'Business',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.school),
            label: 'School',
          ),
        ],
      ),
    );
  }

  Future<String> fetchData() async {
    // 模拟异步操作，返回一个Future
    await Future.delayed(Duration(seconds: 2));
    return 'Hello, World!';
  }
}