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[英]create an instance of Bloc by BlocProvider in initState in flutter
[英]Replacing an instance of a Bloc in a blocprovider
我正在嘗試找到一種方法來創建一個新的 bloc 實例並將其反映在 multibloc 提供程序中。
目前我有以下幾點:
Scaffold(
appBar: AppBar(),
body: MultiBlocProvider(
providers: [
BlocProvider<BlocABloc>(
create: (BuildContext context) => _aBloc,
),
BlocProvider<BlocBBloc>(
create: (BuildContext context) => _bBloc,
),
]...
然后我試圖創建一個新的 BlocABloc 實例和 BlocBBloc 為:
generateNew(){
setState(() {
_aBloc = BlocABloc();
_bBloc = BlocBBloc();
});
}
我期待重新執行構建函數並在 BlocProvider 中使用新實例。 但是,我發現 BlocBuilder 仍在從 Bloc 的前一個實例獲取狀態。
有沒有辦法處理這種情況?
我不知道你為什么要這樣做。 但是您可以使用key
強制再次執行BlocProvider
create 方法。 這是一個如何做到的示例。
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:flutterblocrecreate/bloc_a_bloc.dart';
void main() {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@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;
BlocA _blocA;
@override
void initState() {
super.initState();
_blocA = BlocA(1);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: MultiBlocProvider(
providers: [
BlocProvider<BlocA>(
key: ValueKey(_blocA.state),
create: (context) {
return _blocA;
},
),
],
child: BlocBuilder<BlocA, int>(builder: (context, int state) {
return Column(
children: <Widget>[
SizedBox(
height: 16,
),
Text("Bloc stat: $state"),
SizedBox(
height: 16,
),
Center(
child: RaisedButton(
child: Text("Create New Bloc"),
onPressed: _generateNew,
),
)
],
);
}),
),
);
}
_generateNew() {
setState(() {
_blocA.close();
_blocA = BlocA(2);
});
}
}
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