服务中的依赖注入

Question

我正在尝试 inject dependencies 进入我的应用程序。一切正常，直到我尝试将 Realm 注入我的 Service class。我开始收到 IllegalStateException，这显然是我从创建的 Thread 访问 Realm 造成的。所以，这是我的 Dependency Injection

的结构

AppModule

@Module
public class AppModule {

    MainApplication mainApplication;

    public AppModule(MainApplication mainApplication) {
        this.mainApplication = mainApplication;
    }

    @Provides
    @Singleton
    MainApplication getFmnApplication() {
        return mainApplication;
    }
}

RequestModule

@Module
public class RequestModule {

    @Provides
    @Singleton
    Retrofit.Builder getRetrofitBuilder() {
        return new Retrofit.Builder()
                .baseUrl(BuildConfig.HOST)
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create(CustomGsonParser.returnCustomParser()));
    }

    @Provides
    @Singleton
    OkHttpClient getOkHttpClient() {
        return new OkHttpClient.Builder()
                .addInterceptor(new HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BASIC))
                .connectTimeout(30000, TimeUnit.SECONDS)
                .readTimeout(30000, TimeUnit.SECONDS).build();
    }

    @Provides
    @Singleton
    Retrofit getRetrofit() {
        return getRetrofitBuilder().client(getOkHttpClient()).build();
    }

    @Provides
    @Singleton
    ErrorUtils getErrorUtils() {
        return new ErrorUtils();
    }

    @Provides
    @Singleton
    MainAPI getMainAPI() {
        return getRetrofit().create(MainAPI.class);
    }

    // Used in the Service class
    @Provides
    @Singleton
    GeneralAPIHandler getGeneralAPIHandler(MainApplication mainApplication) {
        return new GeneralAPIHandler(mainApplication, getMainAPIHandler(), getErrorUtils());
    }
}

AppComponent

@Singleton
@Component(modules = {
        AppModule.class,
        RequestModule.class
})
public interface MainAppComponent {

    void inject(SyncService suncService);
}

应用程序Class

public class MainApplication extends Application {

    private MainAppComponent mainAppComponent;

    @Override
    protected void attachBaseContext(Context base) {
        super.attachBaseContext(base);
        MultiDex.install(this);
    }

    @Override
    public void onCreate() {
        super.onCreate();
        mainAppComponent = DaggerMainAppComponent.builder()
                .appModule(new AppModule(this))
                .requestModule(new RequestModule())
                .build();
    }

    public MainAppComponent getMainAppComponent() {
        return mainAppComponent;
    }
}

GeneralAPIHandler

public class GeneralAPIHandler {

    private static final String TAG = "GeneralAPIHandler";
    private MainAPI mainAPI;
    private Realm realm;
    private ErrorUtils errorUtils;
    private Context context;

    public GeneralAPIHandler() {
    }

    public GeneralAPIHandler(MainApplication mainApplication, MainAPI mainAPI, ErrorUtils errorUtils) {
        this.mainAPI = mainAPI;
        this.realm = RealmUtils.getRealmInstance(mainApplication.getApplicationContext());
        this.errorUtils = errorUtils;
        this.context = mainApplication.getApplicationContext();
    }

    public void sendPayload(APIRequestListener apiRequestListener) {
        List<RealmLga> notSentData = realm.where(RealmLga.class).equalTo("isSent", false).findAll(); <-- This is where the error comes from

        .... Other code here
    }
}

只有当我从 Service class 调用它时才会发生这种情况，但是，它是使用应用程序上下文创建的。为什么它会抛出 IllegalStateException

服务Class

public class SyncService extends IntentService {

    @Inject GeneralAPIHandler generalAPIHandler;

    @Override
    public void onCreate() {
        super.onCreate();
        ((MainApplication) getApplicationContext()).getMainAppComponent().inject(this);
    }

    /**
     * Creates an IntentService.  Invoked by your subclass's constructor.
     */
    public SyncService() {
        super("Sync");
    }

    @Override
    protected void onHandleIntent(Intent intent) {
        sendInformations();
    }

    private void sendInformations() {
        generalAPIHandler.sendPayload(new APIRequestListener() {
            @Override
            public void onError(APIError apiError){}

            @Override
            public void didComplete(WhichSync whichSync){}
        })
    }
}

任何关于我做错 Realm throw IllegalStateException 的帮助将不胜感激。谢谢

Answer 1

只需要从创建它的线程访问领域实例。

您的意图服务在后台线程中运行。您的领域可能是在主线程上创建的

Answer 2

@Inject GeneralAPIHandler generalAPIHandler;

@Override
public void onCreate() {
    super.onCreate();
    ((MainApplication) getApplicationContext()).getMainAppComponent().inject(this);
}

因此

public GeneralAPIHandler(MainApplication mainApplication, MainAPI mainAPI, ErrorUtils errorUtils) {
    this.mainAPI = mainAPI;
    this.realm = RealmUtils.getRealmInstance(mainApplication.getApplicationContext()); // <--

此代码在 UI 线程上运行

@Override
protected void onHandleIntent(Intent intent) {
    sendInformations();
}

private void sendInformations() {
    generalAPIHandler.sendPayload(new APIRequestListener() {
    ....


public void sendPayload(APIRequestListener apiRequestListener) {
    List<RealmLga> notSentData = realm.where(RealmLga.class).equalTo("isSent", false).findAll();

此代码在 IntentService 后台线程上运行

尽管处于非循环后台线程中，您也不会关闭 Realm 实例，所以崩溃对您有好处。

解决方法，在onHandleIntent()获取Realm实例，执行结束在finally {关闭。

你可能会说，"but then how will I mock my Constructor argument"，答案是使用 class 比如

@Singleton
public class RealmFactory {
    @Inject
    public RealmFactory() {
    }

    public Realm create() {
        return Realm.getDefaultInstance();
    }
}

服务中的依赖注入

Dependency Injection Into Service

android

realm

dagger-2