Dagger2+Retrofit 更改 URL 与子组件：没有 @Provides- 或 @Produces-annotated 方法无法提供

Question

我是 Dagger 的新手。我在运行时使用更改 URL。

我还使用了三个模块和三个组件，如下所示：

注意：我有两个组件 (ApplicationComponent,ActivityComponent) 和一个子组件 (UrlComponent) 此外，我使用 @Singletone、@PerUrl 和 @PerActivty 作为范围。

当我想 Inject RestApi 进入每个 Activity 我遇到这个错误：

 error: com.example.testdagger2.RestApi cannot be provided without an @Provides- or @Produces-annotated method.
com.example.dagger2.RestApi is injected at
com.example.dagger2.RestApiHelper.restApi
com.example.dagger2.RestApiHelper is injected at
com.example.dagger2.MainActivity.restApiHelper
com.example.testdagger2.MainActivity is injected at
com.example.testdagger2.di.component.ActivityComponent.inject(mainActivity)

在我必须在运行时更改 URL 之前，我有两个组件和模块（appCompoent 和 activtyComponent），所有提供程序（如 Retrofit 和 RestApi ，...）都在 applicationModule 和该程序运行良好。

ApplicationComponent.java

@Singleton
@Component(modules = ApplicationModule.class)
public interface ApplicationComponent {

    void inject(ExampleApplication exampleApplication);

    @ApplicationContext
    Context context();

    Application application();

    UrlComponent plus(UrlModule component);
}

ApplicationModule.java

@Module
public class ApplicationModule {

    private Application mApplication;

    public ApplicationModule(Application application) {
        this.mApplication = application;
    }

        @Provides
        @ApplicationContext
        Context provideContext() {
            return mApplication;
        }

        @Provides
        Application provideApplication() {
            return mApplication;
        }
    }

UrlComponent.java

@PerUrl
@Subcomponent(modules = UrlModule.class)
public interface UrlComponent {

}

UrlModule.java

@Module
public class UrlModule {
    private String url;

    public UrlModule(String url) {
        this.url = url;
    }

    @Provides
    @PerUrl
    OkHttpClient provideOkhttpClient() {
        return new OkHttpClient.Builder()
                .connectTimeout(20, TimeUnit.SECONDS)
                .readTimeout(20, TimeUnit.SECONDS)
                .build();
    }

    @Provides
    @PerUrl
    Retrofit provideRetrofit(String baseURL, OkHttpClient client) {

        return new Retrofit.Builder()
                .baseUrl(baseURL)
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .client(client)
                .build();
    }

    @Provides
    RestApiHelper provideRestApiHelper(RestApiHelper restApiManager) {
        return restApiManager;
    }

    @Provides
    public RestApi provideApiService() {
        return provideRetrofit(url, provideOkhttpClient())
                .create(RestApi.class);

    }
}

ActivityComponent.java

@PerActivity
@Component(modules = ActivityModule.class,dependencies = ApplicationComponent.class)
public interface ActivityComponent {

    void inject(MainActivity mainActivity);
  .
  .
  .

}

ActivityModule.java

@Module
public class ActivityModule {

    private AppCompatActivity mActivity;

    public ActivityModule(AppCompatActivity mActivity) {
        this.mActivity = mActivity;
    }


    @Provides
    @ActivityContext
    Context provideContext() {
        return mActivity;
    }

    @Provides
    AppCompatActivity provideActivity() {
        return mActivity;
    }

   .
   .
   .

}

RestApi.java

public interface RestApi {

    Single<Object> getquestionlist(@Query("page") int page);

    Single<Object> getCategoryList();
}

RestApiHelper.java

public class RestApiHelper implements RestApi {

    @Inject
    RestApi restApi;

    @Inject
    public RestApiHelper(RestApi restApi) {
        this.restApi = restApi;
    }

    @Override
    public Single<Object> getquestionlist(int page) {
        return restApi.getquestionlist(1);
    }

    @Override
    public Single<Object> getCategoryList() {
        return restApi.getCategoryList();
    }

ExampleApplication.java

public class ExampleApplication extends Application {


    @Inject
    ApplicationComponent appComponent;


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

        appComponent = DaggerApplicationComponent.builder()
                .applicationModule(new ApplicationModule(this)).build();
        appComponent.inject(this);
        appComponent.plus(new UrlModule("www/test/en"));


    }

    public ApplicationComponent getAppComponent() {
        return appComponent;
    }


}

BaseActivity.java

public class BaseActivity extends AppCompatActivity {


    ActivityComponent activityComponent;

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

        //activityComponent=DaggerActivityComponent.builder().applicationModule()

        activityComponent= DaggerActivityComponent.builder()
                .applicationComponent(((ExampleApplication)getApplication()).getAppComponent())
                .build();

    }

    public ActivityComponent getActivityComponent() {
        return activityComponent;
    }
}

MainActivity.jaqva

public class MainActivity extends BaseActivity {


    @Inject
    RestApiHelper restApiHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


    ActivityComponent component= getActivityComponent();
    component.inject(this);

        restApiHelper.getquestionlist(1).subscribe(new Consumer<Object>() {
        @Override
        public void accept(Object o) throws Exception {

        }
    });

现在我有两个问题：

1-不应该将 Urlmodule 中内置的所有 Provider 添加到 ApplicationModule(UrlModule is Subcomepoent of the ApplicationComponent )

 @PerActivity
    @Component(modules = ActivityModule.class,dependencies = ApplicationComponent.class)
    public interface ActivityComponent {

并且由于 ApplicationComponent 是一个 Activity 组件依赖项，所有这些 Providers 是否也可以在 Activity 组件中使用？

2-作为一个基本问题，问题出在哪里？

Answer 1

首先你提供RestApi的方法是错误的。我应该像

    @Provides
    public RestApi provideApiService(Retrofit retrofit) {
        return retrofit.create(RestApi.class);

    }

Answer 2

Shouldn't all the Providers built into the Urlmodule be added to ApplicationModule(UrlModule is Subcomepoent of the ApplicationComponent )

当您声明组件依赖项时，依赖组件只能使用在 dependencies 的组件 class 内声明的公开依赖项，在您的情况下，这些是 context 和application 在您的 ApplicationComponent class 中，由 ApplicationModule 提供。

用于验证（测试）：

1) 在您的应用程序模块中添加一个新的 provides

// inside ApplicationModule
@Provides
Student getNum() {
    return new Student("aa");
}

2) 创建并使用 ActivityComponent 对象将 Student 注入任何 class。这将导致缺少供应。它可以通过在 ApplicationComponent class 中公开 Student 来修复：

Student getStu();

2-And as a basic question, where is the problem?

具有以下实现：

Dagger 错误配置的依赖关系图，如上所述
缺少 Rxjava 实施和改造实施
缺少 url 提供等

要解决上述问题，请按照以下步骤操作：

Dagger misconfigured dependancy graph, as explained above

a) MainActivity 需要 UrlComponent 而不是 AppComponent 提供的 RestApiHelper 所以首先使用 UrlComponent 作为依赖而不是 AppComponent

@PerActivity
@Component(modules = ActivityModule.class, dependencies = {UrlComponent.class})
public interface ActivityComponent {

    void inject(MainActivity mainActivity);

}

b) 现在公开 UrlComponent

中的依赖项

@PerUrl
@Subcomponent(modules = UrlModule.class)
public interface UrlComponent {
    RestApiHelper getRetrofit();
}

UrlModule.class 的实施已解决问题（如上所述）

import com.jakewharton.retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
import java.util.concurrent.TimeUnit;    
import dagger.Module;
import dagger.Provides;
import okhttp3.OkHttpClient;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

@Module
public class UrlModule {
    private String url;

    public UrlModule(String url) {
        this.url = url;
    }

    @Provides
    @PerUrl
    OkHttpClient provideOkhttpClient() {
        return new OkHttpClient.Builder()
                .connectTimeout(20, TimeUnit.SECONDS)
                .readTimeout(20, TimeUnit.SECONDS)
                .build();
    }

    @Provides
    String provideUrl() {
        return url;
    }

    @Provides
    @PerUrl
    Retrofit provideRetrofit(String baseURL, OkHttpClient client) {

        return new Retrofit.Builder()
                .baseUrl(baseURL)
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create())
                .client(client)
                .build();
    }


    @Provides
    RestApi provideApiService(Retrofit retrofit) {
        return retrofit.create(RestApi.class);
    }
}

c) 在应用程序 class 中构建 Url appComponent 和 urlComponent 供以后用作

public class ExampleApplication extends Application {

    // note, I remove the inject, you were doing it for testing etc
    private ApplicationComponent appComponent;

    private UrlComponent urlComponent;

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

        appComponent = DaggerApplicationComponent.builder()
                .applicationModule(new ApplicationModule(this)).build();

        urlComponent = appComponent.plus(new UrlModule("https://jsonplaceholder.typicode.com/"));


    }

    public ApplicationComponent getAppComponent() {
        return appComponent;
    }

    public UrlComponent getUrlComponent() {
        return urlComponent;
    }


}

现在将 BaseActivity 中的 activityComponent 构建为

activityComponent= DaggerActivityComponent.builder()
                .activityModule(new ActivityModule(this))
                .urlComponent(((ExampleApplication)getApplication()).getUrlComponent())
                .build();

并在您的 MainActivity 中使用它作为

public class MainActivity extends BaseActivity {


    @Inject
    RestApiHelper restApiHelper;
    Disposable disposable;
    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        ActivityComponent component = getActivityComponent();
        component.inject(this);

        disposable = restApiHelper.getquestionlist(1)
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<Object>() {
                    @Override
                    public void accept(Object o) throws Exception {
                        Log.d(TAG, "accept: "+ o.toString());    
                    }
                }, new Consumer<Throwable>() {
                    @Override
                    public void accept(Throwable throwable) throws Exception {
                        throwable.printStackTrace();
                    }
                });
    }

    @Override
    protected void onDestroy() {
        disposable.dispose(); // best practice
        super.onDestroy();
    }
}

就是这样。

注意：确保您的 baseUrl 值和 retrofit 对象设置正确并且具有互联网应用程序权限等。您可以进一步优化您的代码lambdas 等，因为我保留了大部分代码以供理解。

Dagger2+Retrofit 更改 URL 与子组件：没有 @Provides- 或 @Produces-annotated 方法无法提供

Dagger2+Retrofit change URL with Subcomponent : cannot be provided without an @Provides- or @Produces-annotated method

java

android

retrofit

rx-android

dagger-2