问怎么样保证在build 的时候 pagelist 不为空？

import 'package:dfznapp/pages/person_center/person_center_page.dart';
import 'package:dfznapp/pages/user/user_list_page.dart';
import 'package:dfznapp/utils/constants.dart';
import 'package:flutter/material.dart';
import '../../utils/data_handle.dart';
import 'index_page.dart';


class HomePage extends StatefulWidget {
  static String tag = "home";

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  int _selectedIndex = 0;

  List<StatefulWidget> pagelist=[];
  late int roleid=0;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    _initLoginInfo();

  }

  /// 记住密码的账号密码信息
  void _initLoginInfo() async {
    print("init------------------");
    var res1 = await DataUtil.getData(Constants.LOGIN_ROLEID);
    // var res2 = await DataUtil.getData(Constants.LOGIN_USERID);
    // var res3 = await DataUtil.getData(Constants.LOGIN_USERNAME);
    print("-----------------------");
    roleid=int.parse(res1);
    setState( () {} );
  }


  @override
  Widget build(BuildContext context) {
    print("build------------------");
    if(roleid==1){
      pagelist= [IndexPage(), UserListPage(), PersonCenterPage()];
    }
    if(roleid==2){
      pagelist= [IndexPage(), PersonCenterPage()];
    }
    print(pagelist);
       return Scaffold(
        backgroundColor: Colors.white,
        bottomNavigationBar: BottomNavigationBar(
          type: BottomNavigationBarType.fixed,
          //如果你的icon没有设置color,选中的时候就会用到fixedColor的颜色,当BottomNavigationBarType是BottomNavigationBarType.shifting的时候,这个属性是不起作用的
          //fixedColor: Colors.blue,
          currentIndex: _selectedIndex,
          selectedItemColor: Colors.blue,
          // unselectedItemColor: Colors.amber[800],
          onTap: _onItemTapped,
          items: <BottomNavigationBarItem>[
            BottomNavigationBarItem(
              icon: Icon(
                Icons.home,
              ),
              label: ('首页'),
            ),
            BottomNavigationBarItem(
              icon: Icon(
                Icons.people,
              ),
              label: ('人员列表'),

            ),
            BottomNavigationBarItem(
                icon: Icon(
                  Icons.person,
                ),
                label: (
                  '个人中心'
                )
            ),
          ],
        ),
        body: pagelist[_selectedIndex],
    );
  }

  void _onItemTapped(int index) {
    print("_onItemTapped的index值是："+index.toString());
    setState(() {
      _selectedIndex = index;
    });
  }
}