Delegado de búsqueda, cuando hago clic en el botón Buscar, ¡se muestra una pantalla roja con un niño de error! = nulo
Aug 18 2020
Creo una opción de búsqueda por delegado de búsqueda, pero cuando hago clic en el botón de búsqueda, se muestra la pantalla roja con este error "La siguiente afirmación se lanzó en el edificio _SearchPage (sucio, dependencias: [_LocalizationsScope- [GlobalKey # 69e74], _InheritedTheme], estado: _SearchPageState # 72bb6): 'paquete: flutter / src / widgets / basic.dart': afirmación fallida: línea 6938 pos 15: 'child! = Null': no es cierto.
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>[
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(Icons.search),
onPressed: () {
showSearch(context: context, delegate: DataSearch());
},
),
IconButton(
icon: Icon(
FontAwesomeIcons.heart,
size: 30.0,
),
tooltip: 'My Wish List',
onPressed: () {
Navigator.pushNamed(context, FavouriteScreen.routename);
},
),
IconButton(
icon: Icon(
Icons.notifications,
size: 30.0,
),
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,
color: Colors.white,
),
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,
);
}
}
Respuestas
1 chunhunghan Aug 19 2020 at 14:42
Puede copiar, pegar, ejecutar el código completo a continuación
. Necesita una return
palabra clave en buildSuggestions
Puedereturn ListView.builder
fragmento de código
@override
Widget buildSuggestions(BuildContext context) {
// TODO: implement buildSuggestions
final suggestionList = query.isEmpty
? recentlist
: statelist.where((element) => element.startsWith(query)).toList();
return ListView.builder(
demostración de trabajo

código completo
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,
visualDensity: VisualDensity.adaptivePlatformDensity,
),
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> {
int _counter = 0;
void _incrementCounter() {
setState(() {
_counter++;
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text(widget.title), actions: <Widget>[
IconButton(
icon: Icon(Icons.search),
onPressed: () {
showSearch(context: context, delegate: DataSearch());
},
),
]),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
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();
return 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,
);
}
}