当我单击搜索按钮时，它显示红屏并带有一些脏错误

如何解决当我单击搜索按钮时，它显示红屏并带有一些脏错误

当我单击搜索按钮时，它显示“在构建_SearchPage时抛出了以下断言（脏，相关性：[_LocalizationsScope- [GlobalKey＃69e74]，_InheritedTheme]，状态：_SearchPageState＃72bb6）： 'package：flutter / src / widgets / basic.dart'：失败的断言：6938行pos 15：'child！= null'：不正确。

”

import 'package:flutter/material.dart';
import 'package:grk_001/screen/main_screen.dart';
import 'widgets/entry_item.dart';

import 'package:font_awesome_flutter/font_awesome_flutter.dart';

import 'package:grk_001/screen/favourite_screen.dart';
import 'package:grk_001/Provider/Auth.dart';

import 'package:provider/provider.dart';
import 'package:grk_001/Provider/cart.dart';
import 'package:grk_001/widgets/badge.dart';
import 'package:grk_001/screen/cart_screen.dart';
import 'package:grk_001/widgets/drawer.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:grk_001/models/main_screen_categories_entry.dart';

class HomeScreen extends StatefulWidget {
  static const String routename = 'homescreen';

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

class _HomeScreenState extends State<HomeScreen> {
  final GlobalKey<ScaffoldState> _scaffoldkey = GlobalKey<ScaffoldState>();
  FirebaseUser Loggedinuser;
  @override
  void didChangeDependencies() {
    // TODO: implement didChangeDependencies
    Future.delayed(Duration.zero).then((_) async {
      await Provider.of<Auth>(context,listen: false).getcurrentuser();
    });
    super.didChangeDependencies();
  }

  @override
  Widget build(BuildContext context) {
    final devicesize = MediaQuery.of(context).size;
    return SafeArea(
      child: Scaffold(
        key: _scaffoldkey,appBar: AppBar(
          leading: IconButton(
            onPressed: () {
              _scaffoldkey.currentState.openDrawer();
            },icon: Icon(
              Icons.list,color: Colors.white,size: 35.0,),bottom: PreferredSize(
            preferredSize: const Size.fromHeight(50.0),child: Container(
              padding: const EdgeInsets.all(8.0),child: Row(
                children: <Widget>[
                  Expanded(
                    child: IconButton(
                      icon: Icon(Icons.search),onPressed: () {
                        showSearch(context: context,delegate: DataSearch());
                      },const SizedBox(
                    width: 10.0,Expanded(
                    child: GestureDetector(
                      onTap: () {
                        _scaffoldkey.currentState.openEndDrawer();
                      },child: Container(
                        padding: const EdgeInsets.all(8.0),alignment: Alignment.center,height: 40.0,decoration: BoxDecoration(
                          color: Colors.white,borderRadius: BorderRadius.circular(5.0),child: Text(
                          'Categories',],title: Text('HomeScreen'),actions: <Widget>[
            IconButton(
              icon: Icon(
                FontAwesomeIcons.heart,size: 30.0,tooltip: 'My Wish List',onPressed: () {
                Navigator.pushNamed(context,FavouriteScreen.routename);
              },IconButton(
              icon: Icon(
                Icons.notifications,tooltip: 'My Notifications',onPressed: () {},Consumer<Cart>(
              builder: (_,cartdata,ch) => Badge(
                child: ch,value: cartdata.itemcount.toString(),child: IconButton(
                onPressed: () {
                  Navigator.pushNamed(context,CartScreen.routename);
                },icon: Icon(
                  Icons.shopping_cart,size: 40.0,body: MainScreen(),//        body: CategoryScreen(),endDrawer: Drawer(
          child: Column(
            children: <Widget>[
              Container(
                color: Color(0XFFFF4081),height: devicesize.height * 0.10,child: DrawerHeader(
                    margin: EdgeInsets.zero,child: InkWell(
                      onTap: () {
                        Navigator.of(context).pop();
                      },child: Row(
                        crossAxisAlignment: CrossAxisAlignment.center,mainAxisAlignment: MainAxisAlignment.start,children: <Widget>[
                          Icon(
                            Icons.apps,SizedBox(
                            width: 10.0,Text(
                            'Categories',style:
                                TextStyle(color: Colors.white,fontSize: 20.0),)
//                  child: Text('Categories'),Container(
                height: devicesize.height * 0.85,child: ListView.builder(
                  itemBuilder: (context,index) => EntryItem(data[index]),itemCount: data.length,)
            ],drawer: Container(
          width: devicesize.width * 0.65,child: DrawerItem(devicesize,context),);
  }
}

class DataSearch extends SearchDelegate<String> {
  final statelist = [
    'Andaman and Nicobar Islands','   Andhra Pradesh','Arunachal Pradesh','Assam','Bihar','Chandigarh ','Chhattisgarh','Dadra and Nagar Havel','Daman and Diu','Delhi','Goa','Gujrat','Haryana','Himachal Pradesh','Uttar Pradesh','Uttarakhand','West Bengal','Sikkim','Meghalya','Mizoram',];
  final recentlist = ['Modingar','Ghaziabad','Merrut','Hapur','Delhi'];

  @override
  List<Widget> buildActions(BuildContext context) {
    // action for app bar
    return [
      IconButton(
        onPressed: () {
          query = "";
        },icon: Icon(Icons.clear),)
    ];
  }

  @override
  Widget buildLeading(BuildContext context) {
    // leading icon on the left of the app bar
    return IconButton(
      icon: AnimatedIcon(
        icon: AnimatedIcons.menu_arrow,progress: transitionAnimation,onPressed: () {
        close(context,null);
      },);
  }

  @override
  Widget buildResults(BuildContext context) {
    // TODO: implement buildResults
    return Container(
      height: 150.0,child: Card(
        color: Colors.red,shape: StadiumBorder(),child: Text(query),);
  }

  @override
  Widget buildSuggestions(BuildContext context) {
    // TODO: implement buildSuggestions
    final suggestionList = query.isEmpty
        ? recentlist
        : statelist.where((element) => element.startsWith(query)).toList();
    ListView.builder(
      itemBuilder: (context,index) => ListTile(
          onTap: () {
            showResults(context);
          },title: RichText(
            text: TextSpan(
                text: suggestionList[index].substring(0,query.length),style: TextStyle(
                  color: Colors.black,fontWeight: FontWeight.bold,children: [
                  TextSpan(
                      text: suggestionList[index].substring(query.length),style: TextStyle(color: Colors.grey))
                ]),)),itemCount: suggestionList.length,);
  }
}