Java Dagger-从其他类访问单例对象

我一直在努力理解并设置Dagger来处理我的Android项目的依赖注入。我的单一（非双关语）目标是创建我可以跨应用程序访问的单一对象。我已成功地在初始活动中设置了对象。我被困在从其他类访问这些对象的过程中。以下是我目前的设置：

初始应用程序活动

public class SplashScreenActivity extends AppCompatActivity {

    @Inject SessionKeyExchangerService exchangerService;

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

        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        // establish the session id as a singleton object
        exchangerService = component.provideSessionKeyExchangerService();

        // test whether I can access the singleton from another class
        exchangerService.sendEncryptedKeyToServer();
    } 

组件类

@Singleton
@Component(modules = {AppModule.class})
public interface AppComponent {

    SessionKeyExchangerService provideSessionKeyExchangerService();

    AESCipherService provideCipherService();
}

@Module
public class AppModule {

    @Provides @Singleton
    AESCipherService provideCipherService() {
        return new AESCipherService();
    }

    @Provides @Singleton
    SessionKeyExchangerService provideSessionKeyExchangerService(AESCipherService service) {
        return new SessionKeyExchangerService(service);
    }
}

public class SessionKeyExchangerService {

    private static SessionKeyExchangerService exchanger;
    private AESCipherService cipherService;

    @Inject
    public SessionKeyExchangerService(AESCipherService cipherService) {
        this.cipherService = cipherService;
    }

    public void sendEncryptedKeyToServer () {

        // the next line is almost certainly part of the problem
        // but I don't know how to fix!!!
        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        AESCipherService cipherService = component.provideCipherService();

        Long sessionID = cipherService.getSessionId();
        Log.d(Constants.TAG, "singleton verification: " + (Long.toString(sessionID)));
    }

模块类

@Singleton
@Component(modules = {AppModule.class})
public interface AppComponent {

    SessionKeyExchangerService provideSessionKeyExchangerService();

    AESCipherService provideCipherService();
}

@Module
public class AppModule {

    @Provides @Singleton
    AESCipherService provideCipherService() {
        return new AESCipherService();
    }

    @Provides @Singleton
    SessionKeyExchangerService provideSessionKeyExchangerService(AESCipherService service) {
        return new SessionKeyExchangerService(service);
    }
}

public class SessionKeyExchangerService {

    private static SessionKeyExchangerService exchanger;
    private AESCipherService cipherService;

    @Inject
    public SessionKeyExchangerService(AESCipherService cipherService) {
        this.cipherService = cipherService;
    }

    public void sendEncryptedKeyToServer () {

        // the next line is almost certainly part of the problem
        // but I don't know how to fix!!!
        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        AESCipherService cipherService = component.provideCipherService();

        Long sessionID = cipherService.getSessionId();
        Log.d(Constants.TAG, "singleton verification: " + (Long.toString(sessionID)));
    }

AESCipherService

public class AESCipherService {

    private Long sessionId;

    public AESCipherService() {
        sessionId = makeSessionId();
        Log.d(Constants.TAG, "Session ID: " + Long.toString(sessionId));
    }

    private Long makeSessionId() {
        // this generates a random unsigned integer in the space {0, 2^32-1)
        Random random = new Random();
        return random.nextLong() & 0xffffffffL;
    }

    public Long getSessionId() {
        return sessionId;
    }
}

会话密钥交换类

@Singleton
@Component(modules = {AppModule.class})
public interface AppComponent {

    SessionKeyExchangerService provideSessionKeyExchangerService();

    AESCipherService provideCipherService();
}

@Module
public class AppModule {

    @Provides @Singleton
    AESCipherService provideCipherService() {
        return new AESCipherService();
    }

    @Provides @Singleton
    SessionKeyExchangerService provideSessionKeyExchangerService(AESCipherService service) {
        return new SessionKeyExchangerService(service);
    }
}

public class SessionKeyExchangerService {

    private static SessionKeyExchangerService exchanger;
    private AESCipherService cipherService;

    @Inject
    public SessionKeyExchangerService(AESCipherService cipherService) {
        this.cipherService = cipherService;
    }

    public void sendEncryptedKeyToServer () {

        // the next line is almost certainly part of the problem
        // but I don't know how to fix!!!
        AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

        AESCipherService cipherService = component.provideCipherService();

        Long sessionID = cipherService.getSessionId();
        Log.d(Constants.TAG, "singleton verification: " + (Long.toString(sessionID)));
    }

以下是一些示例输出：

会话ID:217186720
单例验证：790090968

很明显，我不是在访问同一个对象。我意识到，当我试图获取对

AppComponent

类的引用时，我在

AESCipherService

中调用

new

操作符的方式导致了问题的至少一部分，但我不知道如何以任何其他方式获取该引用

我该如何解决这个问题？谢谢

 AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build();

不，不。那不是单身汉。作用域提供程序仅对每个组件起作用，这意味着您必须在整个应用程序中使用单个组件，才能拥有实际共享同一作用域提供程序的

@Singleton

作用域模块。在这种情况下，您将在每次创建活动时创建一个新组件

您需要这样创建它们：

public enum Injector {
    INSTANCE;

    private AppComponent appComponent;

    static {
        INSTANCE.appComponent = DaggerAppComponent.create();
    }

    public getAppComponent() {
        return appComponent;
    }
}

您还可以将

应用程序子类化

，并在

onCreate（）

中创建一个应用程序

也

然后

另外，您正在使用基于

@Module

的实例创建，因此在中的构造函数上丢失

@Inject

@Inject
public SessionKeyExchangerService(AESCipherService cipherService) {
    this.cipherService = cipherService;
}

而且

public void sendEncryptedKeyToServer () {

    // the next line is almost certainly part of the problem
    // but I don't know how to fix!!!
    //AppComponent component = DaggerAppComponent.builder().appModule(new AppModule()).build(); //you don't need this here at all

    //AESCipherService cipherService = component.provideCipherService(); //already provided in constructor