dagger-2 - Dagger 2.11 ContributesAndroidInjector Singleton依赖注入(inject)失败

Question

我正在探索 Dagger 2.11 中的新 dagger.android。我希望不必创建像 @PerActivity 这样的自定义范围注释。到目前为止，我能够执行以下操作:

1) 定义应用程序范围单例并将它们注入(inject)到事件中。

2) 定义 Activity 范围非单例依赖项，并使用 @ContributesAndroidInjector 将它们注入(inject)到其 Activity 中

我不知道如何让应用程序范围单例和事件范围非单例使用它。

在下面的示例中，我希望我的事件范围 MyActivityDependencyA 和 MyActivityDependencyB 能够访问单例 MyActivityService

以下设置结果:

Error:(24, 3) error: com.example.di.BuildersModule_BindMyActivity.MyActivitySubcomponent (unscoped) may not reference scoped bindings: @Singleton @Provides com.example.MyActivityService com.example.MyActivitySingletonsModule.provideMyActivityService()

这是我的设置。请注意，我定义了单独的 MyActivitySingletonsModule 和 MyActivityModule 因为我无法在同一模块文件中混合单例和非单例依赖项。

@Module
public abstract class BuildersModule {
    @ContributesAndroidInjector(modules = {MyActivitySingletonsModule.class, MyActivityModule.class})
    abstract MyActivity bindMyActivity();
    }
}

和

@Module
public abstract class MyActivityModule {
    @Provides
    MyActivityDependencyA provideMyActivityDependencyA(MyActivityService myActivityService){
       return new MyActivityDependencyA(myActivityService);
    }
    @Provides
    MyActivityDependencyB provideMyActivityDependencyB(MyActivityService myActivityService) {
        return new MyActivityDependencyB(myActivityService);
    }
}

和

@Module
public abstract class MyActivitySingletonsModule {
    @Singleton
    @Provides
    MyActivityService provideMyActivityService() {
        return new MyActivityService();
    }
}

和

@Singleton
 @Component(modules = {
    AndroidSupportInjectionModule.class,
    AppModule.class,
    BuildersModule.class})

public interface AppComponent {
    @Component.Builder
    interface Builder {
        @BindsInstance
        Builder application(App application);
        AppComponent build();
    }
    void inject(App app);
}

是否可以在不定义自定义范围注释的情况下完成我想做的事情？

提前致谢!

Answer 1

为什么要避免自定义范围？ Dagger 2.10+ 中引入的新 dagger.android 依赖注入(inject)框架仍然需要自定义作用域。

"My understanding is @ContributesAndroidInjector removes the need for custom annotation and I was able to prove it by using non-singletons defined in the activity scope without any issues."

@ContributesAndroidInjector(在 v2.11 中提供)不会消除对自定义范围的需要。它只是取代了声明 @Subcomponent 类的需要，而这些类不使用 @Subcomponent.Builder 在运行时注入(inject)组件所需的依赖项。看一下 official dagger.android user guide about @ContributesAndroidInjector 中的以下代码片段;

"Pro-tip: If your subcomponent and its builder have no other methods or supertypes than the ones mentioned in step #2, you can use @ContributesAndroidInjector to generate them for you. Instead of steps 2 and 3, add an abstract module method that returns your activity, annotate it with @ContributesAndroidInjector, and specify the modules you want to install into the subcomponent. If the subcomponent needs scopes, apply the scope annotations to the method as well."

@ActivityScope
@ContributesAndroidInjector(modules = { /* modules to install into the subcomponent */ })
abstract YourActivity contributeYourActivityInjector();

这里的关键是“如果子组件需要作用域，请将作用域注释也应用到方法中。”

查看以下代码，了解如何使用 @Singleton、@PerActivity、@PerFragment 和 >@PerChildFragment 使用新的 dagger.android 注入(inject)框架自定义作用域。

// Could also extend DaggerApplication instead of implementing HasActivityInjector
// App.java
public class App extends Application implements HasActivityInjector {

    @Inject
    AppDependency appDependency;

    @Inject
    DispatchingAndroidInjector<Activity> activityInjector;

    @Override
    public void onCreate() {
        super.onCreate();
        DaggerAppComponent.create().inject(this);
    }

    @Override
    public AndroidInjector<Activity> activityInjector() {
        return activityInjector;
    }
}

// AppModule.java
@Module(includes = AndroidInjectionModule.class)
abstract class AppModule {
    @PerActivity
    @ContributesAndroidInjector(modules = MainActivityModule.class)
    abstract MainActivity mainActivityInjector();
}

// AppComponent.java
@Singleton
@Component(modules = AppModule.class)
interface AppComponent {
    void inject(App app);
}

// Could also extend DaggerActivity instead of implementing HasFragmentInjector
// MainActivity.java
public final class MainActivity extends Activity implements HasFragmentInjector {

    @Inject
    AppDependency appDependency; // same object from App

    @Inject
    ActivityDependency activityDependency;

    @Inject
    DispatchingAndroidInjector<Fragment> fragmentInjector;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        AndroidInjection.inject(this);
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main_activity);

        if (savedInstanceState == null) {
            addFragment(R.id.fragment_container, new MainFragment());
        }
    }

    @Override
    public final AndroidInjector<Fragment> fragmentInjector() {
        return fragmentInjector;
    }
}

// MainActivityModule.java
@Module
public abstract class MainActivityModule {
    @PerFragment
    @ContributesAndroidInjector(modules = MainFragmentModule.class)
    abstract MainFragment mainFragmentInjector();
}

// Could also extend DaggerFragment instead of implementing HasFragmentInjector
// MainFragment.java
public final class MainFragment extends Fragment implements HasFragmentInjector {

    @Inject
    AppDependency appDependency; // same object from App

    @Inject
    ActivityDependency activityDependency; // same object from MainActivity

    @Inject
    FragmentDependency fragmentDepency; 

    @Inject
    DispatchingAndroidInjector<Fragment> childFragmentInjector;

    @SuppressWarnings("deprecation")
    @Override
    public void onAttach(Activity activity) {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
            // Perform injection here before M, L (API 22) and below because onAttach(Context)
            // is not yet available at L.
            AndroidInjection.inject(this);
        }
        super.onAttach(activity);
    }

    @Override
    public void onAttach(Context context) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            // Perform injection here for M (API 23) due to deprecation of onAttach(Activity).
            AndroidInjection.inject(this);
        }
        super.onAttach(context);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.main_fragment, container, false);
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        if (savedInstanceState == null) {
            addChildFragment(R.id.child_fragment_container, new MainChildFragment());
        }
    }

    @Override
    public final AndroidInjector<Fragment> fragmentInjector() {
        return childFragmentInjector;
    }
}

// MainFragmentModule.java
@Module
public abstract class MainFragmentModule {
    @PerChildFragment
    @ContributesAndroidInjector(modules = MainChildFragmentModule.class)
    abstract MainChildFragment mainChildFragmentInjector();
}

// MainChildFragment.java
public final class MainChildFragment extends Fragment {

    @Inject
    AppDependency appDependency; // same object from App

    @Inject
    ActivityDependency activityDependency; // same object from MainActivity

    @Inject
    FragmentDependency fragmentDepency; // same object from MainFragment

    @Inject
    ChildFragmentDependency childFragmentDepency;

    @Override
    public void onAttach(Context context) {
        AndroidInjection.inject(this);
        super.onAttach(context);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.main_child_fragment, container, false);
    }
}

// MainChildFragmentModule.java
@Module
public abstract class MainChildFragmentModule {
}

// PerActivity.java
@Scope
@Retention(RetentionPolicy.RUNTIME)
public @interface PerActivity {
}

// PerFragment.java
@Scope
@Retention(RetentionPolicy.RUNTIME)
public @interface PerFragment {
}

// PerChildFragment.java
@Scope
@Retention(RetentionPolicy.RUNTIME)
public @interface PerChildFragment {
}

// AppDependency.java
@Singleton
public final class AppDependency {
    @Inject
    AppDependency() {
    }
}

// ActivityDependency.java
@PerActivity
public final class ActivityDependency {
    @Inject
    ActivityDependency() {
    }
}

// FragmentDependency.java
@PerFragment
public final class FragmentDependency {
    @Inject
    FragmentDependency() {
    }
} 

// ChildFragmentDependency.java
@PerChildFragment
public final class ChildFragmentDependency {
    @Inject
    ChildFragmentDependency() {
    }
}

有关使用 @ContributesAndroidInjector 和上述自定义范围的完整 dagger.android 2.11 设置指南，请阅读 this article .