多个具有相同返回类但键不同的@Binds

以下所有内容均与匕首2.10和dagger.android包装一起使用.

假设我有一个课程,我想在多个活动中注入.

public class DemoSharedClass {
  Activity activity;

  @Inject public DemoSharedClass(Activity activity) {
    this.activity = activity;
  }
}

然后,使用最新的Dagger API,我的类被定义为

public class DemoActivity extends DaggerActivity {
  @Inject DemoSharedClass demoSharedClass;

  // ...
}

public class Demo2Activity extends DaggerActivity {
  @Inject DemoSharedClass demoSharedClass;

  // ...
}

每个活动都将其模块和子组件定义为(exactement相同Demo2Activity)

@Module(subcompOnents= DemoActivitySubcomponent.class)
public abstract class DemoActivityModule {
  @Binds
  @IntoMap
  @ActivityKey(DemoActivity.class)
  abstract AndroidInjector.Factory
    bindDemoActivityInjectorFactory(DemoActivitySubcomponent.Builder builder);

  // This is set so SharedClass can be injected using its constructor
  // There is the same in Demo2ActivityModule
  @Binds abstract Activity bindActivity(DemoActivity demoActivity);
}

@Subcomponent
public interface DemoActivitySubcomponent extends AndroidInjector {
  @Subcomponent.Builder
  abstract class Builder extends AndroidInjector.Builder {}
}

最后,app组件定义为

@Component(modules = {
    ApplicationModule.class,
    AndroidInjectionModule.class,
    DemoActivityModule.class,
    Demo2ActivityModule.class,
})
interface DemoApplicationComponent {
  DemoApplication injectApplication(DemoApplication application);
}

现在,我在构建项目时遇到此错误:

Error:(11, 11) error: [dagger.android.AndroidInjector.inject(T)] android.app.Activity is bound multiple times:
@Binds android.app.Activity dagger.demo.DemoActivityModule.bindActivity(dagger.demo.DemoActivity)
@Binds android.app.Activity dagger.demo.Demo2ActivityModule.bindActivity(dagger.demo.Demo2Activity)

我得到了错误,我认为这是因为它们在相同的范围内,即应用程序组件.

我想到为两个DemoSubcomponents创建一个公共模块,看起来像下面这样,但有类似的错误.

@Module
public abstract class SharedClassModule {
  @Binds abstract Activity bindContext(DemoActivity demoActivity);
  @Binds abstract Activity bindContext(Demo2Activity demo2Activity);
}

问题:我该怎么做？

您需要在每个子组件上单独绑定:

@Module interface DemoActivitySubcomponentModule {
  @Binds abstract Activity bindContext(DemoActivity demoActivity);
  // ...other bindings unique to DemoActivity and not DemoActivity2
}

@Subcomponent(modules={DemoActivitySubcomponentModule.class})
public interface DemoActivitySubcomponent extends 
    AndroidInjector {
  @Subcomponent.Builder
  abstract class Builder extends AndroidInjector.Builder {}
}

因为@BindsInstance Builder seedInstance(DemoActivity)在Dagger 从DispatchingAndroidInjector调用的AndroidInjector.Builder中,Dagger 至少知道如何提供DemoActivity实例.但是,DemoActivity和Activity(或Context)之间没有内置绑定,因此必须在子组件而不是组件上进行绑定.通过将具有该绑定的模块放在适当的上,您可以确保在每个相应的子组件中绑定转到Dagger知道的正确类型.AndroidInjector.Builder.create()@SubcomponentActivity

请注意,@Binds @IntoMap @ActivityKey(...)DemoActivityModule 中的绑定仍然需要转到ApplicationComponent,因此ApplicationComponent可以确定从要注入的Activity的类创建哪个子组件.您特别希望新的DemoActivitySubcomponentModule转到DemoActivitySubcomponent,以便在DemoActivity2Subcomponent无法看到它的地方创建Activity-to-DemoActivity.

作为旁注,您看到的问题是两个绑定之间的冲突Activity,这发生在同一个组件中.说同一个范围是不对的,因为(尽管您可能会选择将@ActivityScope等范围注释添加到每个子组件中),但没有范围注释可以帮助您.这seedInstance将仅适用于每个当前未扩展的子组件,它将与祖先组件中的绑定以及子组件特定的模块组合.