如果没有 @Inject 构造函数或 @Provides 注释的方法，则无法提供 okhttp3.Cache

Question

我正在使用 Android Dagger2，但收到以下错误。\n我的 AppModule 类是：

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@Module\npublic class AppModule {\n\nRetrofitExample retrofitExample;\n\nAppModule(RetrofitExample retrofitExample) {\n\n    this.retrofitExample = retrofitExample;\n\n}\n\n@Singleton\n@Provides\nRetrofitExample provideApplication() {\n    return retrofitExample;\n}\n}\n

\n\n

我的API模块类

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@Module\nclass ApiModule {\n\nString BaseUrl;\n\nprivate  MainActivity  mainActivity;\n\nApiModule(String baseUrl) {\n    this.BaseUrl = baseUrl;\n}\n\n\npublic ApiModule(MainActivity downloadFileView) {\n    this.mainActivity = downloadFileView;\n}\n@Provides\n@Singleton\nGson provideGson() {\n    GsonBuilder gsonBuilder = new GsonBuilder();\n    gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES);\n    return gsonBuilder.create();\n}\n\n@Provides\n@Singleton\nOkHttpClient provideOkhttpClient(Cache cache) {\n    OkHttpClient.Builder client = new OkHttpClient.Builder();\n    client.cache(cache);\n    return client.build();\n}\n\n@Singleton\n@Provides\nRetrofit providesRetrofit(Gson gson, OkHttpClient okHttpClient) {\n    return new Retrofit.Builder()\n            .addConverterFactory(GsonConverterFactory.create(gson))\n            .baseUrl(BaseUrl)\n            .client(okHttpClient)\n            .build();\n}\n\n}\n

\n\n

我的 API 组件类。

\n\n

void inject(MainActivity activity);\n

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这是我的应用程序类

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private static RetrofitExample mInstance;\n\nprivate ApiComponent mApiComponent;\n\n@Override\npublic void onCreate() {\n    super.onCreate();\n\n    mInstance = this;\n\n    mApiComponent = DaggerApiComponent.builder()\n            .appModule(new AppModule(this))\n            .apiModule(new ApiModule("https://simplifiedcoding.net/demos/"))\n            .build();\n}\n\npublic static synchronized RetrofitExample getInstance() { return mInstance;    }\nApiComponent getApiComponent()\n{\n    return mApiComponent;\n}\n

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我收到以下错误

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okhttp3.Cache cannot be provided without an @Inject constructor or from an \n@Provides-annotated method.\nokhttp3.Cache is injected at\nnet.simplifiedlearning.retrofitexample.ApiModule.provideOkhttpClient(cache)\nokhttp3.OkHttpClient is injected at\nnet.simplifiedlearning.retrofitexample.ApiModule.providesRetrofit(\xe2\x80\xa6, \nokHttpClient)\nretrofit2.Retrofit is injected at\nnet.simplifiedlearning.retrofitexample.MainActivity.retrofit\nnet.simplifiedlearning.retrofitexample.MainActivity is injected at\nnet.simplifiedlearning.retrofitexample.ApiComponent.inject(activity)\n

\n

Answer 1

okhttp3.Cache cannot be provided without an @Inject constructor or from an 
@Provides-annotated method.

你需要

@Provides
@Singleton
Cache provideOkHttpCache(Application application) { 
    int cacheSize = 10 * 1024 * 1024; // 10 MiB
    Cache cache = new Cache(application.getCacheDir(), cacheSize);
    return cache;
}

在你的 ApiModule 中。检查与您的类似的 NetModule https://github.com/codepath/android_guides/wiki/Dependency-Injection-with-Dagger-2