Dagger2 - 生成的组件类中的“未使用”模块

Question

My Dagger2 Component class contains 3 modules which I'm trying to use to inject field dependencies into an Android Activity class. The generated Component file has comments saying all the modules are unused, linking this page for more info.

My Activity class is calling the Component's inject(Activity) method and has fields annotated for injection that are provided by the modules, so I am not sure why the generated Component file does not have any Providers to do this injection.

My code is below, thanks for the help!

Generated Component Class:

public final class DaggerMainComponent implements MainComponent {
      private DaggerMainComponent(Builder builder) {
        assert builder != null;
      }

  public static Builder builder() {
    return new Builder();
  }

  public static MainComponent create() {
    return builder().build();
  }

  @Override
  public void inject(Activity activity) {
    MembersInjectors.<Activity>noOp().injectMembers(activity);
  }

  public static final class Builder {
    private Builder() {}

    public MainComponent build() {
      return new DaggerMainComponent(this);
    }

    /**
     * @deprecated This module is declared, but an instance is not used in the component. This method is a no-op. For more, see https://google.github.io/dagger/unused-modules.
     */
    @Deprecated
    public Builder daoModule(DaoModule daoModule) {
      Preconditions.checkNotNull(daoModule);
      return this;
    }

    /**
     * @deprecated This module is declared, but an instance is not used in the component. This method is a no-op. For more, see https://google.github.io/dagger/unused-modules.
     */
    @Deprecated
    public Builder repositoryModule(RepositoryModule repositoryModule) {
      Preconditions.checkNotNull(repositoryModule);
      return this;
    }

    /**
     * @deprecated This module is declared, but an instance is not used in the component. This method is a no-op. For more, see https://google.github.io/dagger/unused-modules.
     */
    @Deprecated
    public Builder portableModule(PortableModule portableModule) {
      Preconditions.checkNotNull(portableModule);
      return this;
    }
  }
}

Non-Generated Component Class :

@Component(modules={DaoModule.class,RepositoryModule.class,PortableModule.class})
public interface MainComponent {
    void inject(Activity activity);
}

Module Classes : Is there any issue with having one module provide an object with a dependency on another object provided by another module belonging to the same Component?

@Module
public class DaoModule {

    private DatabaseHelper databaseHelper;

    public DaoModule(DatabaseHelper databaseHelper){
        this.databaseHelper = databaseHelper;
    }

    @Provides
    public Dao<Player,Integer> providePlayerDao(){
        return databaseHelper.getPlayerDao();
    }

    @Provides
    public Dao<GamePlayed,Integer> provideGamePlayedDao() {
        try {
            return databaseHelper.getDao(GamePlayed.class);
        } catch (SQLException e) {
            return null;
        }
    }

    @Provides
    public Dao<GamePlayer,Integer> provideGamePlayerDao() {
        try {
            return databaseHelper.getDao(GamePlayer.class);
        } catch (SQLException e) {
            return null;
        }
    }
}

...

@Module
public class RepositoryModule {

    @Provides
    public IGameResultRepository provideGameResultRepository(
            Dao<Player,Integer> playerDao,
            Dao<GamePlayed,Integer> gameDao,
            Dao<GamePlayer, Integer> gamePlayerDao)
    {
        return new OrmliteGameResultRepository(playerDao,gameDao,gamePlayerDao);
    }
}

@Module
public class PortableModule {

    @Provides
    public GameResultListener provideGameResultListener(IGameResultRepository gameResultRepository){
        return new GameResultListener(gameResultRepository);
    }

}

Application Class:

public class AppStart extends Application {

    private MainComponent mainComponent;

    @Override
    public void onCreate() {
        super.onCreate();

        DatabaseHelper databaseHelper = new DatabaseHelper(getApplicationContext());

        mainComponent = DaggerMainComponent.builder()
                .daoModule(new DaoModule(databaseHelper))
                .build();
    }

    public MainComponent getMainComponent(){
        return mainComponent;
    }
}

Activity Class:

public class MyActivity extends Activity {

    @Inject GameResultListener gameResultListener;
    @Inject Dao<Player,Integer> dao;
    @Inject IGameResultRepository repository;


    @Override
    protected void onCreate(Bundle state) {
        super.onCreate(state);

        ((AppStart)this.getApplication()).getMainComponent().inject(this);

Answer 1

Question 1: Why are my modules being marked as "unused"?

You have not supplied the correct injection site! As it stands, your component interface is one with the sole injection site of android.app.Activity . Since android.app.Activity has no @Inject annotations on its fields then you get a no-op members injector. Similarly, your modules are marked as unused because none of them are actually being used as sources of dependencies for android.app.Activity . To fix this, in your component change:

void inject(Activity activity);

to:

void inject(MyActivity myActivity);

Question 2:

Is there any issue with having one module provide an object with a dependency on another object provided by another module belonging to the same Component?

No, this is perfectly fine. To illustrate, let's take a simple object graph:

public class Foo {

    public Foo(FooDependency fooDependency) {}
}

public class FooDependency {

    FooDependency(String name) {}
}

We want to inject it inside the following class using Dagger:

public class FooConsumer {

    @Inject Foo foo;

    private FooConsumer() {}
}

We would like to reuse a module binding FooDependency so we'll write two separate modules:

@Module
public class FooModule {

    @Provides
    Foo foo(FooDependency fooDependency) {
        return new Foo(fooDependency);
    }
}

@Module
public class FooDependencyModule {

    @Provides
    FooDependency fooDependency() {
        return new FooDependency("name");
    }
}

And the following component interface:

@Component(modules = {FooModule.class, FooDependencyModule.class})
public interface FooComponent {
    void inject(FooConsumer fooConsumer);
}

The generated component DaggerFooComponent contains the following code that will correctly use the FooDependency from the separate module FooDependencyModule to inject Foo :

  @SuppressWarnings("unchecked")
  private void initialize(final Builder builder) {

    this.fooDependencyProvider =
        FooDependencyModule_FooDependencyFactory.create(builder.fooDependencyModule);

    this.fooProvider = FooModule_FooFactory.create(builder.fooModule, fooDependencyProvider);

    this.fooConsumerMembersInjector = FooConsumer_MembersInjector.create(fooProvider);
  }