11

我有这个全局绑定类来初始化一些服务，我需要立即初始化它：

import 'package:get/get.dart';
import 'package:vepo/data/data_provider/local_data_provider.dart';
import 'package:vepo/data/data_source/local_data_source.dart';

import 'services/authentication_service.dart';

class GlobalBindings extends Bindings {
  final LocalDataProvider _localDataProvider = LocalDataProvider();
  @override
  void dependencies() {
    Get.put<AuthenticationService>(AuthenticationService(), permanent: true);
    Get.put<LocalDataProvider>(_localDataProvider, permanent: true);
    Get.put<LocalDataSource>(LocalDataSource(_localDataProvider),
        permanent: true);
  }
}

在我的初始绑定中：

class App extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GetMaterialApp(
      title: 'Vepo',
      initialRoute: AppPages.INITIAL,
      initialBinding: GlobalBindings(),
      transitionDuration: const Duration(milliseconds: 500),
      defaultTransition: Transition.rightToLeft,
      getPages: AppPages.routes,
      home: Root(),
      theme: homeTheme,
    );
  }
}

然后在类构造函数中我尝试“找到”它：

class UserLocalRepository extends VpService implements IUserLocalRepository {
  UserLocalRepository() {
    localDataSource = Get.find<LocalDataSource>();
  }

  LocalDataSource localDataSource;

并得到这个错误：

══════ Exception caught by widgets library ═══════════════════════════════════
The following message was thrown building App(dirty):
"LocalDataSource" not found. You need to call "Get.put(LocalDataSource())" or "Get.lazyPut(()=>LocalDataSource())"

The relevant error-causing widget was
App
lib/main.dart:17
When the exception was thrown, this was the stack
#0      GetInstance.find
package:get/…/src/get_instance.dart:272
#1      Inst.find
package:get/…/src/extension_instance.dart:66
#2      new UserLocalRepository
package:vepo/…/user/user_local_repository.dart:10
#3      new LoggedOutNickNameBinding
package:vepo/…/logged_out_nickname/logged_out_nick_name_binding.dart:11
#4      AppPages.routes
package:vepo/…/routes/app_pages.dart:29
...
════════════════════════════════════════════════════════════════════════════════

这是错误消息中提到的绑定：

class LoggedOutNickNameBinding extends Bindings {
  LoggedOutNickNameBinding() {
    _repository = Get.put(UserLocalRepository());
  }

  IUserLocalRepository _repository;

  @override
  void dependencies() {
    Get.lazyPut<LoggedOutNickNameController>(
      () => LoggedOutNickNameController(_repository),
    );
  }
}

为什么“initialBindings”没有初始化，以便我的应用程序可以在应用程序启动时“找到”它们？

4

3 回答 3

17

我猜在调用 GlobalBindings.dependencies() 方法以及何时需要这些资源时存在时间/顺序不匹配。

您可以尝试在 GetMaterialApp之前初始化 Bindings 类，而不是将 Bindings 类传递给GetMaterialApp。

void main() async {
  //WidgetsFlutterBinding.ensureInitialized(); // uncomment if needed for resource initialization
  GlobalBindings().dependencies();
  runApp(MyApp());
}

相切

只是在这里猜测，但是您通过 Get.put 初始化的某些类在它们准备好使用之前是慢启动（即异步）吗？

如果是这样，您可以使用

Get.putAsync<YourClass>(() async {
 // init YourClass here
 return await YourClass.slowInit();

}

例子

我最近运行了一个在加载应用程序以供用户交互之前执行异步绑定初始化的练习。这是代码：

import 'package:flutter/material.dart';
import 'package:get/get.dart';

enum Version {
  lazy,
  wait
}
// Cmd-line args/Env vars: https://stackoverflow.com/a/64686348/2301224
const String version = String.fromEnvironment('VERSION');
const Version running = version == "lazy" ? Version.lazy : Version.wait;

void main() async {
  //WidgetsFlutterBinding.ensureInitialized(); // if needed for resources
  if (running == Version.lazy) {
    print('running LAZY version');
    LazyBindings().dependencies();
  }

  if (running == Version.wait) {
    print('running AWAIT version');
    await AwaitBindings().dependencies(); // await is key here
  }

  runApp(MyApp());
}

class LazyBindings extends Bindings {
  @override
  void dependencies() {
    Get.lazyPut<MyDbController>(() => MyDbController());
  }
}

/// Simulates a slow (2 sec.) init of a data access object.
/// Calling [await] dependencies(), your app will wait until dependencies are loaded.
class AwaitBindings extends Bindings {
  @override
  Future<void> dependencies() async {
    await Get.putAsync<MyDbController>(() async {
      Dao _dao = await Dao.createAsync();
      return MyDbController(myDao: _dao);
    });
  }
}

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(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  final MyDbController dbc = Get.find();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('GetX Bindings'),
      ),
      body: Center(
        child: Obx(() => Text(dbc.dbItem.value)),
      ),
    );
  }
}

class MyDbController extends GetxController {
  Dao myDao;

  MyDbController({this.myDao});

  RxString dbItem = 'Awaiting data'.obs;

  @override
  void onInit() {
    super.onInit();
    initDao();
  }

  Future<void> initDao() async {
    // instantiate Dao only if null (i.e. not supplied in constructor)
    myDao ??= await Dao.createAsync();
    dbItem.value = myDao.dbValue;
  }
}

class Dao {
  String dbValue;

  Dao._privateConstructor();

  static Future<Dao> createAsync() async {
    var dao = Dao._privateConstructor();
    print('Dao.createAsync() called');
    return dao._initAsync();
  }

  /// Simulates a long-loading process such as remote DB connection or device
  /// file storage access.
  Future<Dao> _initAsync() async {
    dbValue = await Future.delayed(Duration(seconds: 2), () => 'Some DB data');
    print('Dao._initAsync done');
    return this;
  }
}
于 2020-11-15T05:09:08.510 回答
1

在我的情况下::::

TestCartController? cartController;

if(condition){
 cartController = Get.isRegistered<TestCartController>()
            ? Get.find<TestCartController>()
            : Get.put(TestCartController());

}

但在其他一些小部件中，我将上述控制器称为

final cartController = Get.find<TestCartController>();

类型不匹配问题因为两个实例都不同，所以它给我带来了问题。我只是删除了那个？标记并且它起作用了。

TestCartController cartController;

if(condition){
 cartController = Get.isRegistered<TestCartController>()
            ? Get.find<TestCartController>()
            : Get.put(TestCartController());

}
于 2021-07-30T20:46:45.240 回答
0

原因：在 Get.put(Controller) 之前调用 Get.find() 时发生。在初始化 Get.put() 之前调用 Get.find() 会显示错误

解决方案：您只需将 Get.put(controller) 调用到您的主类中，如下所示。那么任何类的 Get.find() 都会得到它。

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {

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

class _MyAppState extends State<MyApp> {
  final YourController controller = Get.put(YourController());
  ...
  
  @override
  Widget build(BuildContext context) {
  
    return MaterialApp(
    ......
  
}
于 2021-12-14T10:05:10.043 回答