我在设置变量状态时遇到问题,因为我正在使用stateful
小部件之外的其他类。
在buildActions
方法内的第115行,我想设置_selectedStores = selectedStores;
。如何设置状态?
我尝试使用callback
,但是没有运气。
import 'package:flutter/material.dart';
class SearchDemo extends StatefulWidget {
@override
_SearchDemoState createState() => _SearchDemoState();
}
class _SearchDemoState extends State<SearchDemo> {
final _SearchDemoSearchDelegate _delegate = _SearchDemoSearchDelegate();
final GlobalKey<ScaffoldState> _scaffoldKey = GlobalKey<ScaffoldState>();
String _lastSearchSelected;
@override
Widget build(BuildContext context) {
return Scaffold(
key: _scaffoldKey,
appBar: AppBar(
title: const Text('Search Demo'),
actions: <Widget>[
IconButton(
tooltip: 'Search',
icon: const Icon(Icons.search),
onPressed: () async {
final String selected = await showSearch<String>(
context: context,
delegate: _delegate,
);
if (selected != null && selected != _lastSearchSelected) {
setState(() {
_lastSearchSelected = selected;
});
}
},
),
],
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text('Last search: ${_lastSearchSelected ?? 'NONE'}.'),
],
),
),
);
}
}
class Stores {
int id;
String name;
Stores(this.id, this.name);
static List<Stores> getStores() {
return <Stores>[
Stores(1, 'Amazon'),
Stores(2, 'Flipkart'),
Stores(3, 'Snapdeal'),
];
}
}
class _SearchDemoSearchDelegate extends SearchDelegate<String> {
List<Stores> _stores = Stores.getStores();
List<DropdownMenuItem<Stores>> _dropdownMenuItems;
Stores _selectedStores;
List<DropdownMenuItem<Stores>> buildDropdownMenuItems(List stores) {
List<DropdownMenuItem<Stores>> items = List();
for (Stores stores in stores) {
items.add(
DropdownMenuItem(
value: stores,
child: Text(stores.name),
),
);
}
return items;
}
@override
Widget buildLeading(BuildContext context) {
return IconButton(
tooltip: 'Back',
icon: AnimatedIcon(
icon: AnimatedIcons.menu_arrow,
progress: transitionAnimation,
),
onPressed: () {
close(context, null);
},
);
}
@override
Widget buildSuggestions(BuildContext context) {
return _SuggestionList(
query: query,
onSelected: (String suggestion) {
print(suggestion);
},
);
}
@override
Widget buildResults(BuildContext context) {}
@override
List<Widget> buildActions(BuildContext context) {
_dropdownMenuItems = buildDropdownMenuItems(_stores);
_selectedStores = _dropdownMenuItems[0].value;
void onChangeDropdownItem(Stores selectedStores) {
setState(() {
_selectedStores = selectedStores;
});
}
return <Widget>[
query.isEmpty
? Container(
padding: const EdgeInsets.only(right: 5.0, top: 5.0),
child: DropdownButtonHideUnderline(
child: DropdownButton(
elevation: 0,
value: _selectedStores,
items: _dropdownMenuItems,
onChanged: onChangeDropdownItem,
),
),
)
: IconButton(
tooltip: 'Clear',
icon: const Icon(Icons.clear),
onPressed: () {
query = '';
},
),
];
}
}
List<String> getHistory() {
//Get Last Searched products from device storage *Pending*
final List<String> _history = <String>[
"iPhone X 64GB Silver",
"Galaxy S10+ White",
"Apple Watch Series 3",
"Samson C01UPRO",
"Cooler Master masterbox 5"
];
return _history;
}
class _SuggestionList extends StatelessWidget {
const _SuggestionList({this.query, this.onSelected});
final String query;
final ValueChanged<String> onSelected;
@override
Widget build(BuildContext context) {
//Get Data From API *Pending*
final List<String> _data = <String>[
"iPhone X 64GB Silver",
"Galaxy S10+ White",
"Apple Watch Series 3",
"Samson C01UPRO",
"Cooler Master Masterbox 5"
];
final List<String> suggestions = query.isEmpty
? getHistory()
: _data
.where((p) => p.toLowerCase().contains(query.toLowerCase()))
.toList();
return ListView.builder(
itemCount: suggestions.length,
itemBuilder: (BuildContext context, int i) {
final String suggestion = suggestions[i];
return ListTile(
leading: query.isEmpty ? const Icon(Icons.history) : const Icon(null),
title: Text(suggestion),
onTap: () {
onSelected(suggestion);
},
);
},
);
}
}
答案 0 :(得分:0)
方法setState
只是StatefulWidgets
的一部分,因此不应传递信息。不推荐这样做,它也不是一个好的开发实践。你可以做到吗?是的,像这样:
class OtherClass {
final State state;
OtherClass(this.state);
}
class Home extends StatefulWidget {
@override
_HomeState createState() => _HomeState();
}
class _HomeState extends State<Home> {
@override
void initState() {
super.initState();
OtherClass(this);
}
}
但是,再次,我完全不建议这样做。您应该使用某种Future
或Stream
将数据发送到StatefulWidget
,然后在应有的位置使用setState
。