匕首2错误：依赖项“不能在没有@Inject构造函数的情况下提供”，而它实际上是用@Inject注释的

Question

我已经开始使用匕首2，并面临着奇怪的问题，看起来像一个错误给我。

我有3个模块，组成一个子组件，这反过来又扩展/加了更高级别的组件。

子组件非常简单：只需组合模块和单个注入点：

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


    NavigationDrawerFragment inject(NavigationDrawerFragment object);

}

第一个模块看起来像这样-它提供了一般的片段级依赖关系：

@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;
    }
}

第二个模块如下所示-它为屏幕上的UI子集提供演示者/控制器及其依赖项：

@Module
public class SwitcherModule {

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

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

}

第三个模块-UI子集的另一个演示者/控制器：

@Module
public class NavigationListModule {

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

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

正在注射的片段的相关部分：

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

NavigationListControlllerImpl实现以下构造函数：

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

我从Dagger 2编译器得到的错误如下：

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]

错误抱怨缺少@Inject注释构造函数，但它存在！如果我将隐式NavigationListControllerImpl实例创建（通过@传递-方法参数）替换为显式（使用new），dagger开始抱怨相同的错误，但现在是同一模块中的第二个条目presenter对象，依此类推。

所有这些情况看起来都很奇怪，我想听听更有经验的Dagger 2用户（和开发人员？）的一些意见。

提前谢谢你！




Answer 1

我得到了同样的错误，因为我忘记了将父组件中的模块提供的对象公开给依赖它的其他组件。

父组件示例：

@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*/
}

使上述组件成为依赖项的示例组件

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

更新：

应用模块：

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