如何使用Dagger2提供上下文 [英] How to provide Context with Dagger2

问题描述

我正在学习Android，并且正在遵循有关RxJava和Dagger2的Retrofit2的指南. 现在，我不想处理没有互联网连接的情况. 我找到了这个答案， 看起来很优雅，但我不知道如何应用.

I am learning Android and I am following some guides for Retrofit2 with RxJava and Dagger2. Now I want to handle no internet connection case. I've found this answer, which seems to be elegant, but I do not understand how to apply it.

我有一些NetworkModule，并带有OkHttpClient提供程序. 我假设我需要使用拦截器创建OkHttpClient.Builder.所以它应该看起来像这样:`

I've got some NetworkModule, with OkHttpClient provider. I assume I need to create OkHttpClient.Builder with interceptor. So it should look something like this: `

@Provides
@Singleton
OkHttpClient provideOkHttpClient(Cache cache) {
    ConnectivityInterceptor ci = new ConnectivityInterceptor(networkObservable()));
    OkHttpClient.Builder.addInterceptor(ci)
    return builder.build();
}

private boolean networkObservable() {
    ConnectivityManager cm =
            (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);

    NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
    return activeNetwork != null && activeNetwork.isConnectedOrConnecting();
}

这没有用，因为我没有Context. 我应该朝哪个方向去尝试在那儿获取上下文，或者我误解了可观察对象的概念?

This isn't working as I don't have Context. In which direction should I go - to try to obtain context there, or maybe I misunderstand the concept of observables?

推荐答案

您可以在DaggerModule中使用@Provides批注来获取应用程序上下文.或者，您可以创建一个模块，该模块在其构造函数中接受Context参数，以防您需要活动上下文.然后，您可以在活动中构建组件并将参数注入其中.

You can use the @Provides annotation in your DaggerModule to obtain application Context. Alternatively you can create a module which accepts a Context parameter in its constructor in case you need activity context. Then you can build the component in your activity and inject the arguments into it.

 @Module
public class AppModule {

    private Context context;

    public AppModule(@NonNull Context context) {
        this.context = context;
    }

    @Singleton
    @Provides
    @NonNull
    public Context provideContext(){
        return context;
    }

}

应用程序类:

public class PFApplication extends Application {

    private static AppComponent appComponent;

    public static AppComponent getAppComponent() {
        return appComponent;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        appComponent = buildComponent();
    }

    public AppComponent buildComponent(){
        return DaggerAppComponent.builder()
                .appModule(new AppModule(this))
                .build();
    }
}

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