如何解决Flutter/Dart 变量丢失/尝试从不同的类获取时不断重新初始化
从另一个类访问时,变量会不断重新初始化。
我有一个类,在其单独的 dart 源文件中,声明如下:
helper_provider.dart
import 'package:flutter/material.dart';
class BuilderHelperProvider extends ChangeNotifier {
var _builderDetails;
void setBuilderDetails(inputDetails) {
this._builderDetails = inputDetails;
}
get builderDetails {
return _builderDetails;
}
}
然后我在 main.dart 中初始化变量
main.dart
import 'package:builder_project/helpers/helper_provider.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
runApp(MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MultiProvider(
providers: [
ChangeNotifierProvider(
create: (context) => BuilderHelperProvider(),),],child: MaterialApp(
debugShowCheckedModeBanner: false,title: 'Flutter Demo',theme: ThemeData(
primarySwatch: Colors.blue,visualDensity: VisualDensity.adaptivePlatformDensity,home: StreamBuilder(
stream: FirebaseFirestore.instance
.collection('builders')
.doc('builder id')
.snapshots(),builder: (context,builderSnap) {
if (builderSnap.connectionState == ConnectionState.waiting) {
return Center(child: CircularProgressIndicator());
}
final _builderDetails = builderSnap.data;
BuilderHelperProvider().setBuilderDetails(_builderDetails);
print('builder Details: ${BuilderHelperProvider().builderDetails}');
# *This keeps returning null*
return BuilderHomepage();
})
// home: BuilderHomepage(),);
}
}
以上代码的输出如下:
I/flutter (31260): builder Details: null
我的应用程序在两次操作之间没有退出或停止。在什么情况下会被重新初始化?
解决方法
让它们保持静态,你会没事的
static var _builderDetails;
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。