Dagger 2.11 - 组件中存在具有匹配键的绑定

Question

我有一个小场景，我有以下结构，我试图在 baseActivity 片段中注入片段管理器，但由于某种原因，我运行运气不好:(

@Singleton
@Component(modules = { AppModule.class,
        ActivityModule.class,
        AndroidSupportInjectionModule.class })
public interface AppComponent extends AndroidInjector<App> {

    @Override
    void inject(App application);

    @Component.Builder interface Builder {

        @BindsInstance
        AppComponent.Builder application(App application);

        AppComponent build();
    }
}

ActivityModule.class

@PerActivity
@ContributesAndroidInjector(modules = BaseActivityModule.class)
abstract BaseActivity baseActivity();

基地ActivityModule.class

static final String ACTIVITY_FRAGMENT_MANAGER = "ACTIVITY_FRAGMENT_MANAGER";

@PerActivity
@Named(ACTIVITY_FRAGMENT_MANAGER)
@Provides
static FragmentManager activityFragmentManager(BaseActivity activity) {
    return activity.getSupportFragmentManager();
}

BaseAcitivity.class

public abstract class BaseActivity extends DaggerAppCompatActivity {

    @Named(ACTIVITY_FRAGMENT_MANAGER)
    @Inject
    FragmentManager fragmentManager;
}

所以即使我在 BaseActivityModule.class 中提供我的片段管理器，dagger 也会抛出以下错误。我什至尝试只使用 Activity 而不是 BaseActivity 作为我在 BaseActivityModule 中的输入参数。即便如此，我还是陷入了同样的问题。不确定我到底搞砸了什么。所以任何帮助表示赞赏。提前致谢:)

Error:(17, 8) error: [dagger.android.AndroidInjector.inject(T)] @javax.inject.Named("ACTIVITY_FRAGMENT_MANAGER") android.support.v4.app.FragmentManager cannot be provided without an @Provides- or @Produces-annotated method.
@javax.inject.Named("ACTIVITY_FRAGMENT_MANAGER") android.support.v4.app.FragmentManager is injected at
com.abc.views.base.BaseActivity.fragmentManager
com.abc.views.def.ABCActivity is injected at
dagger.android.AndroidInjector.inject(arg0)
A binding with matching key exists in component: om.abc.views.base.BaseActivity_BaseActivity.BaseActivitySubcomponent

Answer 1

"A binding with matching key exists in component" 表示您在整个对象图中的某处绑定了一个依赖项，但无法从需要注入它的子组件到达它。这是 javadoc:

Utility code that looks for bindings matching a key in all subcomponents in a binding graph so that a user is advised that a binding exists elsewhere when it is not found in the current subgraph. If a binding matching a key exists in a sub- or sibling component, that is often what the user actually wants to use.

例如，假设您有两个活动，ActivityA 和 ActivityB。您使用 @ContributesAndroidInjector 生成子组件并在 ActivityA 模块中绑定 Foo 而不是 ActivityB 模块。如果您请求使用 @Inject Foo foo 在 ActivityB 中注入 Foo，您将收到该错误消息。

在像 BaseActivity 这样的基础 class 上使用 @ContributesAndroidInjector 形成子组件可能不是一个好的方法。就像 David Medenjak 的评论一样，基础 class 的子组件将被忽略，具体 class 的子组件将在 ABCActivity 上执行注入。

现在，您可以通过在 ABCActivity:

的子组件中绑定 FragmentManager 来修复错误

@PerActivity
@ContributesAndroidInjector(modules = BaseActivityModule.class)
abstract ABCActivity ABCActivity();

Dagger 2.11 - 组件中存在具有匹配键的绑定

Dagger 2.11 - A binding with matching key exists in component

android

dependency-injection

dagger

dagger-2