Dagger 2 error: dependency "cannot be provided without an @Inject constructor" while it actually annotated with @Inject

Question

I've started using Dagger 2 and faced strange issue that looks like a bug to me.

I have 3 modules, that are composed into one subcomponent, which in turn extends/pluses higher level component.

Subcomponent is pretty simple: just combination of modules and a single injection point:

@Singleton
@Subcomponent(
        modules = {
                NavigationDrawerModule.class,
                NavigationListModule.class,
                SwitcherModule.class
        }
)
public interface NavigationDrawerComponent {


    NavigationDrawerFragment inject(NavigationDrawerFragment object);

}

First modules looks like this - it provides general fragment-level dependencies:

@Module
public class NavigationDrawerModule {

    private final Activity activity;
    private final View rootView;
    private final LoaderManager loaderManager;

    public NavigationDrawerModule(Activity activity, View rootView, LoaderManager loaderManager) {
        this.activity = activity;
        this.rootView = rootView;
        this.loaderManager = loaderManager;
    }

    @Provides @Singleton EventBus provideLocalBus() {
        return EventBus.builder().build();
    }

    @Provides @Singleton View provideViewRoot() {
        return rootView;
    }

    @Provides @Singleton LoaderManager provideLoaderManager() {
        return loaderManager;
    }

    @Provides @Singleton Context provideContext() {
        return activity;
    }
}

Second module looks like this - it provides presenter/controller and their dependencies for a subset of UI on screen:

@Module
public class SwitcherModule {

    @Provides SwitchController provideSwitcherController(SwitchControllerImpl impl) {
        return impl;
    }

    @Provides SwitcherView provideSwitcherView(SwitcherViewImpl impl) {
        return impl;
    }

}

Third module - another presenter/controller for a subset of UI:

@Module
public class NavigationListModule {

    @Provides @Singleton NavigationListController provideNavigationListController(NavigationListControllerImpl impl) {
        return impl;
    }

    @Provides @Singleton NavigationListView provideNavigationListView(NavigationListViewImpl impl) {
        return impl;
    }
}

Relevant part of the fragment that is being injected:

@Inject SwitchController identitySwitchController;
@Inject SwitcherView identitySwitcherView;
@Inject NavigationListController navigationListController;
@Inject NavigationListView navigationListView;

NavigationListControllerImpl implements the following constructor:

@Inject
public NavigationListControllerImpl(Context ctx, EventBus bus) {
    this.ctx = ctx;
    this.bus = bus;
}

Error I'm getting from the Dagger 2 compiler is the following:

error: ...sidenavigation.navigationlist.NavigationListControllerImpl cannot be provided without an @Inject constructor or from an @Provides-annotated method.
...sidenavigation.NavigationDrawerFragment.navigationListController
[injected field of type: ...sidenavigation.navigationlist.NavigationListController navigationListController]
...sidenavigation.navigationlist.NavigationListModule.provideNavigationListController(...sidenavigation.navigationlist.NavigationListControllerImpl impl)
[parameter: ...sidenavigation.navigationlist.NavigationListControllerImpl impl]

Error complains about missing @Inject-annotated constructor, but it exists! If I replace implicit NavigationListControllerImpl instance creation (passing via @Provides-method parameter) with explicit (with new), dagger starts complaining about the same error but now for the presenter object which is the second entry in the same module, and so on.

All this situation looks very strange, and I'd like to hear some input from more experienced Dagger 2 users (and developers?).

Thank you in advance!

Answer 1

I got this same error because I forgot to expose the objects provided by the modules in the parent component to the other components that are depend on it.

Parent component example:

@Singleton
@Component(modules = {AppModule.class})
public interface AppComponent {
    AppPref exposeAppPref(); /* my issue was caused by forgot this line,
the method name doesn't matter, what matters is the object type AppPref provided in the AppModule 
that you want it to be available in the component that declares this component as one of its dependencies*/
}

Sample component that makes the above component as a dependency

@UserScope
@Component (dependencies = {AppComponent.class})
public interface ActivityComponent {
    void inject(MainActivity activity);
}

Update:

AppModule:

...
    @Provides
    @Singleton
    AppPref provideAppPref() {
        return appPref;
    }
...

Answer 2

The GlobalComponent and the subcomponent NavigationDrawerComponent must have different scopes. Use @Singleton for your GlobalComponent and some another scope for the subcomponent.

Otherwise, if you apply the same scope to the GlobalComponent and to the subcomponent, you must declare the modules of your subcomponent in your global component as well:

@Component(
        // modules from subcomponent must be declared here also
        modules = {NavigationListModule.class, 
                  SwitcherModule.class, 
                  NavigationDrawerModule.class,
                  ...}
)
@Singleton
public interface GlobalComponent {
   NavigationDrawerComponent plus(NavigationDrawerModule module);
}

For your use case, you can also use component dependencies. For instance:

@Component(
        dependencies = GlobalComponent.class,
        modules = {NavigationListModule.class, 
                  SwitcherModule.class, 
                  NavigationDrawerModule.class}
)
@YourOtherDaggerScope // @Singleton scope won't work here, it must be a different scope
public interface NavigationDrawerComponent extends GlobalComponent { // extend the parent component if you wish to get access to parent dependencies

   NavigationDrawerFragment inject(NavigationDrawerFragment object);
}

Answer 3

Seems like I've figured out what was wrong with my Dagger 2 setup. It's not possible to use the same scope in both component and subcomponents. It's required to define a new scope for subcomponent. In my case I've ended up creating @Screen scope for me subcomponent.

I'd say that this is a small but very annoying defect in Dagger 2. Apparently dagger-compiler reports nice and understandable error about the same scopes in a parent component and child component if child component is extended with a parent component as dependency. But completely misleading error is reported by the compiler if parent component and child subcomponent share the same scope.

Thank you, @lukas, for giving me a hint here https://stackoverflow.com/a/30383088/808313 that led to a problem resolution.

Answer 4

Came accross this issue today too. For me there was a problem with the Annotation processing (on Android Studio 2.2 with gradle 2.x).

Instead of ~~apt~~ I used annotationProcessor I used

annotationProcessor 'com.google.dagger:dagger-compiler:2.6'

and now It's working.