如何解决 dagger 错误 - 如果没有 @Inject 构造函数或 @Provides-annotated 方法，则无法提供字符串

Question

Hi I have a PdfTicketStorage class which has a constructor which accepts 2 parameters, I have added @Inject to the constructor and also it in the MockServiceOrderModule. but I get an error

MockAppComponent.java:48: error: [Dagger/MissingBinding] java.lang.String cannot be provided without an @Inject constructor or an @Provides-annotated method.

full error is

/home/circleci/code/app/src/androidTest/java/com/xx/xxx/test/injection/components/MockAppComponent.java:48: error: [Dagger/MissingBinding] java.lang.String cannot be provided without an @Inject constructor or an @Provides-annotated method.
public interface MockAppComponent extends AppComponent {
       ^
      java.lang.String is injected at
          com.xxx.xx.test.injection.modules.MockServiceOrderModule.providePdfTicketStorage(cloudStorageBucket, …)
      com.xxx.xx.printing.storage.PdfTicketStorage is injected at
          com.xxx.xx.clean.offline.OfflineHelper(…, pdfTicketStorage, …)
      com.xxx.xx.clean.offline.OfflineHelper is injected at
          com.xxx.xx.clean.offline.repository.OfflineUserApiRepository(…, offlineHelper)
      com.xxx.xx.clean.offline.repository.OfflineUserApiRepository is injected at
          com.xxx.xx.clean.florder.data.repository.flOrderRepository(offlineUserApiRepository, …)
      com.xxx.xx.clean.florder.data.repository.flOrderRepository is injected at
          com.xxx.xx.test.scenarios.BaseScenario.flOrderRepository
      com.xxx.xx.test.scenarios.BaseScenario is injected at
          com.xxx.xx.test.injection.components.MockAppComponent.inject(com.xxx.xx.test.scenarios.BaseScenario)
  The following other entry points also depend on it:
      com.xxx.xx.test.injection.components.MockAppComponent.inject(com.xxx.xx.test.scenarios.VehicleTakeoverScenario)
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.activities.MainActivity) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.fragments.fller.florder.BaseflOrderFragment) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.fragments.fller.florder.BaseflOrderDataFragment) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.fragments.fller.florder.flOrderDataFragment) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.fragments.fller.florder.flOrderSummaryFragment) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.fragments.fller.florder.flOrderDeallocationFragment) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.clean.orderslist.serviceorders.view.ServiceOrderListFragment) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.fragments.fller.florder.ServiceOrderViewFragment) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      com.xxx.xx.injection.components.ActivityComponent.inject(com.xxx.xx.clean.orderslist.serviceorders.view.ServiceOrderAdapter) [com.xxx.xx.test.injection.components.MockAppComponent → com.xxx.xx.injection.components.ActivityComponent]
      and 31 others/home/circleci/code/app/src/androidTest/java/com/xx/xxx/test/injection/components/MockAppComponent.java:48: error: [Dagger/MissingBinding] java.lang.String cannot be provided without an @Inject constructor or an @Provides-annotated method.

PdfTicketStorage

@PerApp
public class PdfTicketStorage {

    private final String cloudStorageBucket;
    private final Lazy<OfflineHelper> offlineHelper;

    @Inject
    public PdfTicketStorage(String cloudStorageBucket, Lazy<OfflineHelper> offlineHelper) {
        this.cloudStorageBucket = cloudStorageBucket;
        this.offlineHelper = offlineHelper;
    }
}

OfflineHelper

@PerApp
class OfflineHelper @Inject constructor(
    private val app: App,
    private val settings: Settings,
    private val pdfTicketStorage: PdfTicketStorage,
    @Named("default") private val gson: Gson
) 

MockServiceOrderModule

@Module
public class MockServiceOrderModule {

      @Provides @PerApp
    PdfTicketStorage providePdfTicketStorage(String cloudStorageBucket, Lazy<OfflineHelper> offlineHelper) {
        return new PdfTicketStorage(cloudStorageBucket, offlineHelper);
    }

}

Could you suggest what am I doing wrong here please

your suggestions on how can I resolve this please this would be very helpful

thanks R

Answer 1

Dagger's acyclic graph does not know how to provide the type String , in the case of String cloudStorageBucket . There are two solutions:

1. Either create another @Provides for String . This is not recommended as you'll run into issue if another String type is required.
2. (Recommended) Mark the @Provides in the 1 with @Named("cloudStorageBucket") .

You can also use @assisted-inject if this String will be provided at runtime.

Answer 2

First of all, When you are already providing the object here in this dagger module:

@Module
public class MockServiceOrderModule {

      @Provides @PerApp
    PdfTicketStorage providePdfTicketStorage(String cloudStorageBucket, Lazy<OfflineHelper> offlineHelper) {
        return new PdfTicketStorage(cloudStorageBucket, offlineHelper);
    }

}

You don't need to use constructor injection in PdfTicketStorage class. You can just inject the object and use then like this:

@PerApp
public class PdfTicketStorage {

    @Inject
    public PdfTicketStorage pdfTicketStorage;
}

But also you have to make sure to provides the string in dagger module also. Not sure why you need to provide the string in dagger module?